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AMC 20-3B Certification of Engines Equipped with Electronic Engine Control Systems

Available versions for ERULES-1963177438-8992

ED Decision 2020/010/R found in: AMC-20 Amdt 22 - Airworthiness of Products, Parts and Appliances (May 2021)

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AMC 20-3B Certification of Engines Equipped with Electronic Engine Control Systems

ED Decision 2020/010/R

(1) PURPOSE

The existing certification specifications of CS-E for Engine certification may require specific interpretation for Engines equipped with Electronic Engine Control Systems (EECS), with special regard to interface with the certification of the aircraft and/or Propeller when applicable. Because of the nature of this technology, it has been considered useful to prepare acceptable means of compliance (AMC) specifically addressing the certification of these control systems.

Like any AMC, it is issued to outline issues to be considered during the demonstration of compliance with CS-E.

(2) SCOPE

This AMC is relevant to Engine certification specifications for EECS, whether they use electrical or electronic (analogue or digital) technology. This is in addition to other AMC such as AMC E 50 or AMC E 80.

It gives guidance on the precautions to be taken for the use of electrical and electronic technology for Engine control, protection, limiting and monitoring functions, and, where applicable, for the integration of aircraft or Propeller functions. In the latter case, this document is applicable to such functions integrated into the EECS, but only to the extent that these functions affect compliance with CS-E specifications.

The text deals mainly with the thrust and power functions of an EECS, since this is the prime function of the Engine. However, there are many other functions, such as bleed valve control, that may be integrated into the system for operability reasons. The principles outlined in this AMC apply to the whole EECS.

This document also discusses the division of compliance tasks for certification between the applicants for Engine, Propeller (when applicable), and aircraft type certificates. This guidance relates to issues to be considered during Engine certification. [AMC 20-1()](#_DxCrossRefBm1701657975) addresses issues associated with the Engine installation in the aircraft.

The introduction of electrical and electronic technology can entail the following:

— greater dependence of the Engine on the aircraft owing to the increased use of electrical power or data supplied from the aircraft;

— increased integration of control and related indication functions;

— increased risk of significant Failures that are common to more than one Engine of the aircraft which might, for example, occur as a result of:

— insufficient protection from electromagnetic disturbance (e.g. lightning, internal or external radiation effects) (see CS-E 50(a)(1), CS E-80 and CS-E 170);

— insufficient integrity of the aircraft electrical power supply (see CS-E 50(h));

— insufficient integrity of data supplied from the aircraft (see CS-E 50(g));

— hidden design Faults or discrepancies contained within the design of the propulsion system control software or airborne electronic hardware (AEH) (see CS-E 50(f)); or

— omissions or errors in the system/software/AEH specification (see CS-E 50(f)).

Appropriatedesign and integration precautions should therefore be taken to minimise any adverse effects from the above.

(3) RELEVANT SPECIFICATIONS AND REFERENCE DOCUMENTS

Although compliance with many CS-E specifications might be affected by the Engine Control System, the main paragraphs relevant to the certification of the Engine Control System itself are the following:

<table border="1" cellpadding="0" cellspacing="0" width="570"><tr><td valign="top" width="348">CS-E Specification</td><td valign="top" width="108">Turbine Engines</td><td valign="top" width="114">Piston Engines</td></tr><tr><td valign="top" width="348">CS-E 20 (Engine configuration and interfaces)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 25 (Instructions for Continued Airworthiness)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 30 (Assumptions)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 50 (Engine Control System)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 60 (Provision for instruments)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 80 (Equipment)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 110 (Drawing and marking of parts — Assembly of parts)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 130 (Fire prevention)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 140 (Tests-Engine configuration)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 170 (Engine systems and component verification)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 210 (Failure analysis)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 250 (Fuel System)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 390 (Acceleration tests)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 500 (Functioning)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E-510 (Safety analysis)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 560 (Fuel system)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 745 (Engine Acceleration)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr><tr><td valign="top" width="348">CS-E 1030 (Time-limited dispatch)</td><td valign="top" width="108"></td><td valign="top" width="114"></td></tr></table>

The following documents are referenced in AMC 20-3B:

— International Electrotechnical Commission (IEC), Central Office, 3, rue de Varembé, P.O. Box 131, CH - 1211 GENEVA 20, Switzerland

— IEC/PAS 62239, Electronic Component Management Plans, edition 1.0, dated April 2001

— IEC/PAS 62240, Use of Semiconductor Devices Outside Manufacturers’ Specified Temperature Ranges, edition 1.0, dated April 2001

— RTCA, Inc. 1828 L Street, NW, Suite 805, Washington, DC 20036 or EUROCAE, 17, rue Hamelin, 75116 Paris, France

— RTCA DO-254/ EUROCAE ED-80, Design Assurance Guidance for Airborne Electronic Hardware, dated April 19, 2000

— RTCA DO-160/EUROCAE ED 14, Environmental Conditions and Test Procedures for Airborne Equipment

— [AMC 20-115](#_DxCrossRefBm1701657978) on software considerations for certification of airborne systems and equipment

— Aeronautical Systems Center, ASC/ENOI, Bldg 560, 2530 Loop Road West, Wright‑Patterson AFB, OH, USA, 45433-7101

— MIL-STD-461E, Requirements for the Control of Electromagnetic Interference Characteristics, dated August 20, 1999

— MIL-STD-810 E or F, Test Method Standard for Environmental Engineering, E dated July 14, 1989, F dated January 1, 2000

— U.S. Department of Transportation, Subsequent Distribution, Office Ardmore East Business Center, 3341 Q 75th Ave, Landover, MD, USA, 20785

— AC 20-136, Protection of Aircraft Electrical/Electronic Systems Against the Indirect Effects of Lightning, dated March 5, 1990

— Society of Automotive Engineers (SAE), 400 Commonwealth Drive, Warrendale, PA 15096-0001 USA or EUROCAE, 17, rue Hamelin, 75116 Paris, France

— SAE ARP 5412 / EUROCAE ED-84, with Amendment 1 & 2, Aircraft Lightning Environment and Related Test Waveforms, February 2005/May 2001 respectively

— SAE ARP 5413 / EUROCAE ED-81, with Amendment 1, Certification of Aircraft Electrical/Electronic Systems for the Indirect Effects of Lightning, November 1999/August 1999 respectively

— SAE ARP 5414 / EUROCAE ED-91, with Amendment 1, Aircraft Lightning Zoning, February 2005/June 1999 respectively

— SAE ARP 5416 / EUROCAE ED-105, Aircraft Lightning Test Methods, March 2005/April 2005 respectively

(4) DEFINITIONS

The words defined in CS-Definitions and in CS-E 15 are identified by capital letters.

The following figure and associated definitions are provided to facilitate a clear understanding of the terms used in this AMC.

<table cellpadding="0" cellspacing="0" width="100%"><tr><td><div>DEFINITIONS VISUALISED</div></td></tr></table>

<table cellpadding="0" cellspacing="0" width="100%"><tr><td><div>SYSTEMS</div></td></tr></table>

<table cellpadding="0" cellspacing="0" width="100%"><tr><td><div>Primary system May be one or more lanes (channels) Lanes typically have equal functionality</div></td></tr></table>

<table cellpadding="0" cellspacing="0" width="100%"><tr><td><div>ENGINE CONTROL SYSTEM</div></td></tr></table>

<table cellpadding="0" cellspacing="0" width="100%"><tr><td><div>Backup systemMay be hydromechanicalcontrol or less capable lane</div></td></tr></table>

<table cellpadding="0" cellspacing="0" width="100%"><tr><td><div>ALTERNATE MODE 1ALTERNATE MODE 2BACKUP MODE 1BACKUP MODE 2</div></td></tr></table>

<table cellpadding="0" cellspacing="0" width="100%"><tr><td><div>MODES</div></td></tr></table>

<table cellpadding="0" cellspacing="0" width="100%"><tr><td><div>PRIMARY MODE / NORMAL MODE</div></td></tr></table>

<table cellpadding="0" cellspacing="0" width="100%"><tr><td><div>ALTERNATE MODES</div></td></tr></table>

(5) GENERAL

It is recognised that the determination of compliance of the Engine Control System with the applicable aircraft certification specifications will only be made during the aircraft certification.

In the case where the installation is unknown at the time of Engine certification, the applicant for Engine certification should make reasonable installation and operational assumptions for the target installation. Any installation limitations or operational issues will be noted in the instructions for installation or operation, and/or the Type Certificate Data Sheet (TCDS) (see CS‑E 30 Assumptions).

When possible, early coordination between the Engine and the aircraft applicants is recommended in association with the relevant authorities as discussed under Section 15 of this AMC.

(6) SYSTEM DESIGN AND VALIDATION

(a) Control Modes — General

Under CS-E 50(a), the applicant should perform all necessary testing and analysis to ensure that all Control Modes, including those which occur as a result of control Fault Accommodation strategies, are implemented as required.

The need to provide protective functions, such as overspeed protection, for all Control Modes, including any Alternate Modes, should be reviewed under the specifications of CS-E 50(c), (d) and (e), and CS-E 210 or CS-E 510.

Any limitations on operations in Alternate Modes should be clearly stated in the Engine instructions for installation and operation.

Descriptions of the functioning of the Engine Control System operating in its Primary and any Alternate Modes should be provided in the Engine instructions for installation and operation.

Analyses and/or testing are necessary to substantiate that operating in the Alternate Modes has no unacceptable effect on Engine durability or endurance. Demonstration of the durability and reliability of the control system in all modes is primarily addressed by the component testing of CS-E 170. Performing some portion of the Engine certification testing in the Alternate Mode(s) and during transition between modes can be used as part of the system validation required under CS-E 50(a).

(i) Engine Test Considerations

If the Engine certification tests defined in CS-E are performed using only the Engine Control System’s Primary Mode in the Full-up Configuration and if approval for dispatch in the Alternate Mode is requested by the applicant under CS-E 1030, it should be demonstrated, by analysis and/or test, that the Engine can meet the defined test-success criteria when operating in any Alternate Mode that is proposed as a dispatchable configuration as required by CS-E 1030.

Some capabilities, such as operability, blade-off, rain, hail, bird ingestion, etc., may be lost in some control modes that are not dispatchable. These modes do not require engine test demonstration as long as the installation and operating instructions reflect this loss of capability.

(ii) Availability

Availability of any Back-up Mode should be established by routine testing or monitoring to ensure that the Back-up Mode will be available when needed. The frequency of establishing its availability should be documented in the Instructions for Continued Airworthiness (ICA).

(b) Crew Training Modes

This AMC is not specifically intended to apply to any crew training modes. These modes are usually installation-, and possibly operator-, specific and need to be negotiated on a case-by-case basis. As an example, one common application of crew training modes is for simulation of the ‘failed-fixed’ mode on a twin-engine rotorcraft. Training modes should be described in the Engine instructions for installation and operation as appropriate. Also, precautions should be taken in the design of the Engine Control System and its crew interfaces to prevent inadvertent entry into any training modes. Crew training modes, including lock-out systems, should be assessed as part of the System Safety Analysis (SSA) of CS-E 50(d).

For control configurations which are not dispatchable, but for which the applicant seeks to take credit in the system Loss of Thrust (or Power) Control (LOTC/LOPC) analysis, it may be acceptable to have specific operating limitations. In addition, compliance with CS‑E 50(a) does not imply strict compliance with the operability specifications of CS-E 390, CS-E 500 and CS-E 745 in these non-dispatchable configurations, if it can be demonstrated that, in the intended installation, no likely pilot control system inputs will result in Engine surge, stall, flame-out or unmanageable delay in power recovery. For example, in a twin-engine rotorcraft, a rudimentary Backup System may be adequate since frequent and rapid changes in power setting with the Backup System may not be necessary.

In addition to these operability considerations, other factors which should be considered in assessing the acceptability of such reduced-capability Backup Modes include:

— the installed operating characteristics of the Back-up Mode and the differences from the Primary Mode;

— the likely impact of the Back-up Mode operations on pilot workload, if the aircraft installation is known;

— the frequency of transfer from the Primary Mode to the Back-up Mode (i.e. the reliability of the Primary Mode);frequencies of transfer of less than 1 per 20 000 engine flight hours have been considered acceptable.

(d) Control Transitions

The intent of CS-E 50(b) is to ensure that any control transitions, which occur as a result of Fault Accommodation, occur in an acceptable manner.

In general, transition to Alternate Modes should be accomplished automatically by the Engine Control System. However, systems for which pilot action is required to engage the Backup Mode may also be acceptable. For instance, a Fault in the Primary System may result in a ‘failed-fixed’ fuel flow and some action is required by the pilot to engage the Backup System in order to modulate Engine power. Care should be taken to ensure that any reliance on manual transition is not expected to pose an unacceptable operating characteristic, unacceptable crew workload or require exceptional skill.

The transient change in power or thrust associated with transfer to Alternate Modes should be reviewed for compliance with CS-E 50(b). If available, input from the installer should be considered. Although this is not to be considered a complete list, some of the items that should be considered when reviewing the acceptability of Control Mode transitions are:

— The frequency of occurrence of transfers to any Alternate Mode and the capability of the Alternate Mode. Computed frequency-of-transfer rates should be supported with data from endurance or reliability testing, in-service experience on similar equipment, or other appropriate data.

— The magnitude of the power, thrust, rotor or Propeller speed transients.

— Successful demonstration, by simulation or other means, of the ability of the Engine Control System to control the Engine safely during the transition. In some cases, particularly those involving rotorcraft, it may not be possible to make a determination that the mode transition provides a safe system based solely on analytical or simulation data. Therefore, a flight test programme to support this data will normally be expected.

— An analysis should be provided to identify those Faults that cause Control Mode transitions either automatically or through pilot action.

— For turboprop or turboshaft engines, the transition should not result in excessive overspeed or underspeed of the rotor or Propeller which could cause emergency shutdown, loss of electrical generator power or the setting-off of warning devices.

The thrust or power change associated with the transition should be declared in the instructions for installing the Engine.

(i) Time Delays

Any observable time delays associated with Control Mode, channel or system transitions or in re-establishing the pilot’s ability to modulate Engine thrust or power should be identified in the Engine instructions for installation and operation (see CS-E 50(b)). These delays should be assessed during aircraft certification.

(ii) Annunciation to the Flight Crew

If annunciation is necessary to comply with CS-E 50(b)(3), the type of annunciation to the flight crew should be commensurate with the nature of the transition. For instance, reversion to an Alternate Mode of control where the transition is automatic and the only observable changes in operation of the Engine are different thrust control schedules, would require a very different form of annunciation to that required if timely action by the pilot is required in order to maintain control of the aircraft.

The intent and purpose of the cockpit annunciation should be clearly stated in the Engine instructions for installation and operation, as appropriate.

(e) Environmental conditions

Environmental conditions include electromagnetic interference (EMI), high-intensity radiated fields (HIRF) and lightning. The environmental conditions are addressed under CS-E 80 and CS-E 170. The following provides additional guidance for EMI, HIRF and lightning.

(i) Declared levels

When the installation is known during the Engine type-certification programme, the Engine Control System should be tested at levels that have been determined and agreed by the Engine and aircraft applicants. It is assumed that, by this agreement, the installation can meet the aircraft certification specifications. Successful completion of the testing to the agreed levels would be accepted for Engine type certification. This, however, may make the possibility of installing the Engine dependent on a specific aircraft.

If the aircraft installation is not known or defined at the time of the Engine certification, in order to determine the levels to be declared for the Engine certification, the Engine applicant may use the external threat level defined at the aircraft level and use assumptions on installation attenuation effects.

If none of the options defined above are available, it is recommended that the procedures and minimum default levels for HIRF testing should be agreed with EASA.

(ii) Test procedures

(A) General

The installed Engine Control System, including representative
 Engine–aircraft interface cables, should be the basis for certification testing.

EMI test procedures and test levels conducted in accordance with MIL‑STD‑461 or EUROCAE ED 14/DO-160 have been considered acceptable.

The applicant should use the HIRF test guidelines provided in EUROCAE ED 14/RTCA DO-160 or equivalent. However, it should be recognised that the tests defined in EUROCAE ED 14/RTCA DO-160 are applicable at a component test level, requiring the applicant to adapt these test procedures to a system level HIRF test to demonstrate compliance with CS-E 80 and CS‑E 170.

For lightning tests, the guidelines of SAE ARP 5412, 5413, 5414 and 5416, and EUROCAE ED 14/RTCA DO-160 would be applicable.

Pin Injection Tests (PIT) are normally conducted as component tests on the EECS unit and other system components as required. PIT levels are selected as appropriate from the tables of EUROCAE ED 14/DO-160.

Environmental tests, such as MIL-STD-810, may be accepted in lieu of EUROCAE ED-14/DO-160 tests where these tests are equal to or more rigorous than those defined in EUROCAE ED 14/DO-160.

(B) Open-loop and Closed-loop Testing

HIRF and lightning tests should be conducted as system tests on closed-loop or open-loop laboratory set-ups.

The closed-loop set-up is usually provided with hydraulic pressure to move actuators to close the inner actuating loops. A simplified Engine simulation may be used to close the outer Engine loop.

Testing should be conducted with the Engine Control System controlling at the most sensitive operating point, as selected and detailed in the test plans by the applicant. The system should be exposed to the HIRF and lightning environmental threats while operating at the selected condition. There may be a different operating point for HIRF and lightning environmental threats.

For tests in open- and closed-loop set-ups, the following factors should also be considered:

— If a special EECS test software is used, that software should be developed at the criticality level determined by the Engine safety assessment process.

— The Engine Control System should be tested at the criticality levels that have been determined and agreed by the Engine and aircraft applicants. It is assumed that by this agreement, the installation meets the aircraft certification specifications. In some cases, the application code is modified to include the required test code features.

— The system test set-up should be capable of monitoring both the output signals and the input signals.

— Anomalies observed during open-loop testing on inputs or outputs should be duplicated on the Engine simulation to determine whether the resulting power or thrust perturbations comply with the pass–fail criteria.

(iii) Pass–Fail Criteria

The pass–fail criteria of CS-E 170 for HIRF and lightning should be interpreted as ‘no adverse effect’ on the functionality of the system.

The following are considered adverse effects:

— a greater than 3 % change of Take-off Power or Thrust for a period of more than 2 seconds;

— transfers to Alternate Channels, Backup Systems, or Alternate Modes;

— component damage;

— false annunciation to the flight crew, which could cause unnecessary or inappropriate flight crew action;

— erroneous operation of protection systems, such as overspeed or thrust reverser circuits.

AEH or software design changes implemented after the initial environmental testing should be evaluated for their effects with respect to the EMI, HIRF and lightning environment.

(iv) Maintenance Actions

CS-E 25 requires that the applicant prepare Instructions for Continued Airworthiness (ICA). These include a maintenance plan. Therefore, for any protection system that is part of the type design of the Engine Control System and is required by the system to meet the qualified levels of EMI, HIRF and lightning, a maintenance plan should be provided to ensure the continued airworthiness for the parts of the installed system which are supplied by the Engine type-certificate holder.

The maintenance actions to be considered include periodic inspections or tests for required structural shielding, wire shields, connectors, and equipment protection components. Inspections or tests when the part is exposed may also be considered. The applicant should provide the engineering validation and substantiation of these maintenance actions.

(v) Time-Limited Dispatch (TLD) Environmental Tests

Although TLD is only an optional requirement for certification (see CS-E 1000 and CS-E 1030), EMI, HIRF and lightning tests for TLD are usually conducted together with tests conducted for certification. Acceptable means of compliance are provided in AMC E 1030.

(7) INTEGRITY OF THE ENGINE CONTROL SYSTEM

(a) Objective

The intent of CS-E 50(c) is to establish Engine Control System integrity requirements consistent with operational requirements of the various installations. (See also paragraph (4) of AMC E 50).

(b) Definition of an LOTC/LOPC event

(i) For turbine Engines intended for CS-25 installations

An LOTC/LOPC event is defined as an event where the Engine Control System:

— has lost the capability of modulating thrust or power between idle and 90% of maximum rated power or thrust, or

— suffers a Fault which results in a thrust or power oscillation greater than the levels given in paragraph (7)(c) of this AMC, or

— has lost the capability to govern the Engine in a manner which allows compliance with the operability specifications given in CS-E 500(a) and CS-E 745.

(ii) For turbine Engines intended for rotorcraft

An LOPC event is defined as an event where the Engine Control System:

— has lost the capability of modulating power between idle and 90% of maximum rated power at the flight condition, except OEI power ratings, or

— suffers a Fault which results in a power oscillation greater than the levels given in paragraph (7)(c) of this AMC, or

— has lost the capability to govern the Engine in a manner which allows compliance with the operability specifications given in CS-E 500(a) and CS-E 745, with the exception that the inability to meet the operability specifications in the Alternate Modes may not be included as LOPC events.

— Single Engine rotorcraft will be required to meet the operability specifications in the Alternate Mode(s), unless the lack of this capability is demonstrated to be acceptable at the aircraft level. Engine operability in the Alternate Mode(s) is considered a necessity if:

— the control transitions to the Alternate Mode more frequently than the acceptable LOPC rate, or

— normal flight crew activity requires rapid changes in power to safely fly the aircraft.

— For multi-Engine rotorcraft, the LOPC definition may not need to include the inability to meet the operability specifications in the Alternate Mode(s). This may be considered acceptable because when one Engine control transitions to an Alternate Mode, which may not have robust operability, that Engine can be left at reasonably fixed power conditions. The Engine(s) with the normally operating control(s) can change power – as necessary – to complete aircraft manoeuvres and safely land the aircraft. Demonstration of the acceptability of this type of operation may be required at aircraft certification.

(iii) For turbine Engines intended for other installations

A LOTC/LOPC event is defined as an event where the Engine Control System:

— has lost the capability of modulating thrust or power between idle and 90% of maximum rated power or thrust, or

— suffers a Fault which results in a thrust or power oscillation that would impact controllability in the intended installation, or

— has lost the capability to govern the Engine in a manner which allows compliance with the operability specifications given in CS-E 500(a) and CS-E 745, as appropriate.

(iv) For piston Engines

An LOPC event is defined as an event where the Engine Control System:

— has lost the capability of modulating power between idle and 85% of maximum rated power at all operating conditions, or

— suffers a Fault which results in a power oscillation greater than the levels given in paragraph (7)(c) of this AMC, or

— has lost the capability to govern the Engine in a manner which allows compliance with the operability specifications given in CS-E 390.

(v) For engines incorporating functions for Propeller control integrated in the EECS

The following Faults or Failures should be considered as additional LOPC events:

— inability to command a change in pitch,

— uncommanded change in pitch,

— uncontrollable Propeller torque or speed fluctuation.

Any uncommanded thrust or power oscillations should be of such a magnitude as not to impact aircraft controllability in the intended installation. Thrust or power oscillations less than 10% peak to peak of Take-off Power and/or Thrust have been considered acceptable in some installations, where the failure affects one engine only. Regardless of the levels discussed herein, if the flight crew has to shut down an Engine because of unacceptable thrust or power oscillations caused by the control system, such an event would be deemed an in-service LOTC/LOPC event.

(d) Acceptable LOTC/LOPC rate

The applicant may propose an LOTC/LOPC rate other than those below. Such a proposal should be substantiated in relation to the criticality of the Engine and control system relative to the intended installation. The intent is to show equivalence of the LOTC/LOPC rate to existing systems in comparable installations.

(i) For turbine Engines

The EECS should not cause more than one LOTC/LOPC event per 100 000 engine flight hours.

(ii) For piston Engines

An LOPC rate of 45 per million engine flight hours (or 1 per 22,222 engine flight hours) has been shown to represent an acceptable level for the most complex EECS. As a result of the architectures used in many of the EECS for these engines, the functions are implemented in independent system elements. These system elements or sub-systems can be fuel control, or ignition control, or others. If a system were to contain only one element such as fuel control, then the appropriate total system level would be 15 LOPC events per million engine flight hours. So the system elements are then additive up to a max of 45 LOPC events per million hours. For example, an EEC system comprised of fuel, ignition, and wastegate control functions should meet a total system reliability of 15+15+15 = 45 LOPC events per million engine flight hours. This criterion is then applied to the entire system and not allocated to each of the subsystems. Note that a maximum of 45 LOPC events per million engine flight hours are allowed, regardless of the number of subsystems. For example, if the EEC system includes more than three subsystems, the sum of the LOPC rates for the total system should not exceed 45 LOPC events per million engine flight hours for all of the electrical and electronic elements.

(e) LOTC/LOPC Analysis

A system reliability analysis should be submitted to substantiate the agreed LOTC/LOPC rate for the Engine Control System. A numerical analysis such as a Markov model analysis, fault tree analysis or equivalent analytical approach is expected.

The analysis should address all components in the system that can contribute to LOTC/LOPC events. This includes all electrical, mechanical, hydromechanical, and pneumatic elements of the Engine Control System. This LOTC/LOPC analysis should be done in conjunction with the System Safety Assessment required under CS-E 50(d). Paragraph (8) of this AMC provides additional guidance material.

The engine fuel pump is generally not included in the definition of the Engine Control System. It is usually considered part of the fuel delivery system.

The LOTC/LOPC analysis should include those sensors or elements which may not be part of the Engine type design, but which may contribute to LOTC/LOPC events. An example of this is the throttle or power lever transducer, which is usually supplied by the installer. The effects of loss, corruption or Failure of Aircraft-Supplied Data should be included in the Engine Control System’s LOTC/LOPC analysis. The reliability and interface requirements for these non-Engine type design elements should be contained in the Engine instructions for installation. It needs to be ensured that there is no double counting of the rate of Failure of non-engine parts within the aircraft system safety analyses.

The LOTC/LOPC analysis should consider all Faults, both detected and undetected. Any periodic maintenance actions needed to find and repair both Covered and Uncovered Faults, in order to meet the LOTC/LOPC rate, should be contained in the Engine instructions for continued airworthiness.

(f) Commercial or Industrial Grade Electronic Parts

When the Engine type design specifies commercial or industrial grade electronic components, which are parts not manufactured to military standards, the applicant should have the following data available for review, as applicable:

— Reliability data that substantiates the Failure rate for each component used in the LOTC/LOPC analysis and the SSA for each commercial and industrial grade electrical component specified in the design.

— The applicant’s procurement, quality assurance, and process control plans for the vendor-supplied commercial and industrial grade parts. These plans should ensure that the parts will be able to maintain the reliability level specified in the approved Engine type design.

— Unique databases for similar components obtained from different vendors, because commercial and industrial grade parts may not all be manufactured to the same accepted industry standard, such as military component standards.

— Commercial and industrial grade parts have typical operating ranges of 0 degrees to +70 degrees Celsius and -40 degrees to +85 degrees Celsius, respectively. Military grade parts are typically rated at -54 degrees to 125 degrees Celsius. Commercial and industrial grade parts are typically defined in these temperature ranges in vendor parts catalogues. If the declared temperature environment for the Engine Control System exceeds the stated capability of the commercial or industrial grade electronic components, the applicant should substantiate that the proposed extended range of the specified components is suitable for the installation and that the Failure rates used for those components in the SSA and LOTC/LOPC analyses is appropriately adjusted for the extended temperature environment. Additionally, if commercial or industrial parts are used in an environment beyond their specified rating and cooling provisions are required in the design of the EECS, the applicant should specify these provisions in the instructions for installation to ensure that the provisions for cooling are not compromised. Failure modes of the cooling provisions included in the EECS design that cause these limits to be exceeded should be considered in determining the probability of Failure.

— Two examples of industry published documents which provide guidance on the application of commercial or industrial grade components are:

— IEC/PAS 62239, Electronic Component Management Plans

— IEC/PAS 62240, Use of Semiconductor Devices Outside Manufacturers’ Specified Temperature Ranges

When any electrical or electronic components are changed, the SSA and LOTC/LOPC analyses should be reviewed with regard to the impact of any changes in component reliability. Component, subassembly or assembly level testing may be required by the Agency to substantiate a change that introduces a commercial or industrial part(s). However, such a change would not be classified as ‘significant’ with respect to Part 21.A.101(b)1.

(g) Single Fault Accommodation

Compliance with the single Fault specifications of CS-E 50(c)(2) and (3) may be substantiated by a combination of tests and analyses. The intent is that single Failures or malfunctions in the Engine Control System’s components, in its fully operational condition, do not result in a Hazardous Engine Effect. In addition, in its full-up configuration the control system should be essentially single Fault tolerant of electrical/electronic component Failures with respect to LOTC/LOPC events. For dispatchable configurations refer to CS-E 1030 and AMC E 1030.

It is recognised that to achieve true single Fault tolerance for LOTC/LOPC events could require a triplicated design approach or a design approach with 100% Fault detection. Currently, systems have been designed with dual, redundant channels or with Back-up Systems that provide what has been called an "essentially single Fault tolerant" system. Although these systems may have some Faults that are not Covered Faults, they have demonstrated excellent in-service safety and reliability, and have proven to be acceptable.

The objective, of course, is to have all the Faults addressed as Covered Faults. Indeed, the dual channel or Back-up system configurations do cover the vast majority of potential electrical and electronic Faults. However, on a case-by-case basis, it may be appropriate for the applicant to omit some coverage because detection or accommodation of some electrical/electronic Faults may not be practical. In these cases, it is recognised that single, simple electrical or electronic components or circuits can be employed in a reliable manner, and that requiring redundancy in some situations may not be appropriate. In these circumstances, Failures in some single electrical or electronic components, elements or circuits may result in an LOTC/LOPC event. This is what is meant by the use of the term “essentially”, and such a system may be acceptable.

(h) Local Events

Examples of local events to be considered under CS-E 50(c)(4) include:

— Overheat conditions, for example, those resulting from hot air duct bursts,

— Fires, and

— Fluid leaks or mechanical disruptions which could lead to damage to control system electrical harnesses, connectors, or the control unit(s).

These local events would normally be limited to one Engine. Therefore, a local event is not usually considered to be a common mode event, and common mode threats, such as HIRF, lightning and rain, are not considered local events.

When demonstration that there is no Hazardous Engine Effect is based on the assumption that another function exists to afford the necessary protection, it should be shown that this function is not rendered inoperative by the same local event on the Engine (including destruction of wires, ducts, power supplies).

It is considered that an overheat condition exists when the temperature of the system components is greater than the maximum safe design operating temperature for the components, as declared by the Engine applicant in the Engine instructions for installation. The Engine Control System should not cause a Hazardous Engine Effect when the components or units of the system are exposed to an overheat or over-temperature condition. Specific design features or analysis methods may be used to show compliance with respect to the prevention of Hazardous Engine Effects. Where this is not possible, for example, due to the variability or the complexity of the Failure sequence, then testing may be required.

The Engine Control System, including the electrical, electronic and mechanical parts of the system, should comply with the fire specifications of CS-E 130 and the interpretative material of AMC E 130 is relevant. This rule applies to the elements of the Engine Control System which are installed in designated fire zones.

There is no probability associated with CS-E 50(c)(4). Hence, all foreseeable local events should be considered. It is recognised, however, that it is difficult to address all possible local events in the intended aircraft installation at the time of Engine certification. Therefore, sound Engineering judgement should be applied in order to identify the reasonably foreseeable local events. Compliance with this specification may be shown by considering the end result of the local event on the Engine Control System. The local events analysed should be well documented to aid in certification of the Engine installation.

The following guidance applies to Engine Control System wiring:

— Each wire or combination of wires interfacing with the EECS that could be affected by a local event should be tested or analysed with respect to local events. The assessment should include opens, shorts to ground and shorts to power (when appropriate) and the results should show that Faults result in identified responses and do not result in Hazardous Engine Effects.

— Engine control unit aircraft interface wiring should be tested or analysed for shorts to aircraft power, and these “hot” shorts should result in an identified and non-Hazardous Engine Effect. Where aircraft interface wiring is involved, the installer should be informed of the potential effects of interface wiring Faults by means of information provided in the Engine instructions for installation. It is the installer’s responsibility to ensure that there are no wiring Faults which could affect more than one Engine. Where practical, wiring Faults should not affect more than one channel. Any assumptions made by the Engine applicant regarding channel separation should be included in the LOTC/LOPC analysis.

— Where physical separation of conductors is not practical, co-ordination between the Engine applicant and the installer should ensure that the potential for common mode Faults between Engine Control Systems is eliminated, and between channels on one Engine is minimised.

The applicant should assess by analysis or test the effects of fluid leaks impinging on components of the Electronic Engine Control System. Such conditions should not result in a Hazardous Engine Effect, nor should the fluids be allowed to impinge on circuitry or printed circuit boards and result in a potential latent Failure condition.

(8) SYSTEM SAFETY ASSESSMENT

(a) Scope of the assessment

The system safety assessment (SSA) required under CS-E 50(d) should address all operating modes, and the data used in the SSA should be substantiated.

The LOTC/LOPC analysis described in Section 7 is a subset of the SSA. The LOTC/LOPC analysis and SSA may be separate or combined as a single analysis.

The SSA should consider all Faults, both detected and undetected, and their effects on the Engine Control System and the Engine itself. The intent is primarily to address the Faults or malfunctions which only affect one Engine Control System, and therefore only one Engine. However, Faults or malfunctions in aircraft signals, including those in a multi-engine installation that could affect more than one Engine, should also be included in the SSA; these types of Faults are addressed under CS-E 50(g).

The Engine Control System SSA and LOTC/LOPC analysis, or combined analyses, should identify the applicable assumptions and installation requirements and establish any limitations relating to Engine Control System operation. These assumptions, requirements, and limitations should be stated in the Engine instructions for installation and operation as appropriate. If necessary, the limitations should be contained in the airworthiness limitations section of the instructions for continued airworthiness in accordance with CS-E 25(b)(1).

The SSA should address all Failure effects identified under CS-E 510 or CS-E 210, as appropriate. A summary should be provided, listing the malfunctions or Failures and their effects caused by the Engine Control System, such as:

— Failures affecting power or thrust resulting in LOTC/LOPC events.

— Failures which result in the Engine’s inability to meet the operability specifications. If these Failure cases are not considered as LOPC events according to paragraph (7)(b)(ii) of this AMC, the expected frequency of occurrence for these events should be documented.

— Transmission of erroneous parameters which could lead to thrust or power changes greater than 3% of Take-off Power or Thrust (10% for piston engines installations) (e.g., false high indication of the thrust or power setting parameter) or to Engine shutdown (e.g., high EGT or turbine temperatures or low oil pressure).

— Failures affecting functions included in the Engine Control System, which may be considered aircraft functions (e.g. Propeller control, thrust reverser control, control of cooling air, control of fuel recirculation)

— Failures resulting in Major Engine Effects and Hazardous Engine Effects.

The SSA should also consider all signals used by the Engine Control System, in particular any cross-Engine control signals and air signals as described in CS-E 50(i).

The criticality of functions included in the Engine Control System for aircraft level functions needs to be defined by the aircraft applicant.

(b) Criteria

The SSA should demonstrate or provide the following:

(i) Compliance with CS-E 510 or CS-E 210, as appropriate.

(ii) For Failures leading to LOTC/LOPC events,compliance with the agreed LOTC/LOPC rate for the intended installation (see paragraph (7)(d) of this AMC).

(iii) For Failures affecting Engine operability but not leading to LOPC events,compliance with the expected total frequency of occurrence of Failures that result in Engine response that is non-compliant with CS-E 390, CS-E 500(a) and CS-E 745 specifications (as appropriate). The acceptability of the frequency of occurrence for these events - along with any aircraft flight deck indications deemed necessary to inform the flight crew of such a condition - will be determined at aircraft certification.

(iv) The consequence of the transmission of a faulty parameter

The consequence of the transmission of a faulty parameter by the Engine Control System should be identified and included, as appropriate, in the LOTC/LOPC analysis. Any information necessary to mitigate the consequence of a faulty parameter transmission should be contained in the Engine operating instructions.

For example, the Engine operating instructions may indicate that a display of zero oil pressure be ignored in-flight if the oil quantity and temperature displays appear normal. In this situation, Failure to transmit oil pressure or transmitting a zero oil pressure signal should not lead to an Engine shutdown or LOTC/LOPC event. Admittedly, flight crew initiated shutdowns have occurred in-service during such conditions. In this regard, if the Engine operating instructions provide information to mitigate the condition, then control system Faults or malfunctions leading to the condition do not have to be included in the LOTC/LOPC analysis. In such a situation, the loss of multiple functions should be included in the LOTC/LOPC analysis. If the display of zero oil pressure and zero oil quantity (or high oil temperature) would result in a crew initiated shutdown, then those conditions should be included in the systems LOTC/LOPC analysis.

In multi-engine aeroplanes, Faults that result in thrust or power changes of less than approximately 10% of Take-off Power or Thrust may be undetectable by the flight crew. This level is based on pilot assessment and has been in use for a number of years. The pilots indicated that flight crews will note the Engine operating differences when the difference is greater than 10% in asymmetric thrust or power.

The detectable difference level for Engines for other installations should be agreed with the installer.

When operating in the take-off envelope, Uncovered Faults in the Engine Control System which result in a thrust or power change of less than 3% (10% for piston engines installations), are generally considered acceptable. However, this does not detract from the applicant’s obligation to ensure that the full-up system is capable of providing the declared minimum rated thrust or power. In this regard, Faults which could result in small thrust changes should be random in nature and detectable and correctable during routine inspections, overhauls or power-checks.

The frequency of occurrence of Uncovered Faults that result in a thrust or power change greater than 3% of Take-off Power or Thrust, but less than the change defined as an LOTC/LOPC event, should be contained in the SSA documentation. There are no firm specifications relating to this class of Faults for Engine certification; however the rate of occurrence of these types of Faults should be reasonably low, in the order of 10-4 events per Engine flight hour or less. These Faults may be required to be included in aircraft certification analysis.

Signals sent from one Engine Control System to another in an aeroplane installation, such as signals used for an Automatic Take-off Thrust Control System (ATTCS), synchrophasing, etc., are addressed under CS-E 50(g). They should be limited in authority by the receiving Engine Control System, so that undetected Faults do not result in an unacceptable change in thrust or power on the Engine using those signals. The maximum thrust or power loss on the Engine using a cross-Engine signal should generally be limited to 3% absolute difference of the current operating condition.

Note: It is recognised that ATTCS, when activated, may command a thrust or power increase of 10% or more on the remaining Engine(s). It is also recognised that signals sent from one Engine control to another in a rotorcraft installation, such as load sharing and One Engine Inoperative (OEI), can have a much greater impact on Engine power when those signals fail. Data of these Failure modes should be contained in the SSA.

When operating in the take-off envelope, detected Faults in the Engine Control System, which result in a thrust or power change of up to 10% (15% for piston engines) may be acceptable if the total frequency of occurrence for these types of Failures is relatively low. The predicted frequency of occurrence for this category of Faults should be contained in SSA documentation. It should be noted that requirements for the allowable frequency of occurrence for this category of Faults and any need for a flight deck indication of these conditions would be reviewed during aircraft certification. A total frequency of occurrence in excess of 10–4 events per Engine flight hour would not normally be acceptable.

Detected Faults in signals exchanged between Engine Control Systems should be accommodated so as not to result in greater than a 3% thrust or power change on the Engine using the cross-Engine signals.

(9) PROTECTIVE FUNCTIONS

(a) Rotor Over-speed Protection.

Rotor over-speed protection is usually achieved by providing an independent over-speed protection system, such that it requires two independent Faults or malfunctions (as described below) to result in an uncontrolled over-speed.

The following guidance applies if the rotor over-speed protection is provided solely by an Engine Control System protective function.

For dispatchable configurations, refer to CS-E 1030 and AMC E 1030.

The SSA should show that the probability per Engine flight hour of an uncontrolled over-speed condition from any cause in combination with a Failure of the over-speed protection system to function is less than one event per hundred million hours (a Failure rate of 10–8 events per Engine flight hour).

The over-speed protection system would be expected to have a Failure rate of less than 10–4 Failures per engine flight hour to ensure the integrity of the protected function.

A self-test of the over-speed protection system to ensure its functionality prior to each flight is normally necessary for achieving the objectives. Verifying the functionality of the over-speed protection system at Engine shutdown and/or start-up is considered adequate for compliance with this requirement. It is recognised that some Engines may routinely not be shut down between flight cycles. In this case this should be accounted for in the analyses.

Because in some over-speed protection systems there are multiple protection paths, there will always be uncertainty that all paths are functional at any given time. Where multiple paths can invoke the over-speed protection system, a test of a different path may be performed each Engine cycle. The objective is that a complete test of the over-speed system, including electro-mechanical parts, is achieved in the minimum number of Engine cycles. This is acceptable so long as the system meets a 10-4 Failure rate.

The applicant may provide data that demonstrates that the mechanical parts (this does not include the electro-mechanical parts) of the over-speed protection system can operate without Failure between stated periods, and a periodic inspection may be established for those parts. This data is acceptable in lieu of testing the mechanical parts of the sub-system each Engine cycle.

(b) Other protective functions

The Engine Control System may perform other protective functions. Some of these may be Engine functions, but others may be aircraft or Propeller functions. Engine functions should be considered under the guidelines of this AMC. The integrity of other protective functions provided by the Engine Control System should be consistent with a safety analysis associated with those functions, but if those functions are not Engine functions, they may not be a part of Engine certification.

As Engine Control Systems become increasingly integrated into the aircraft and Propeller systems, they are incorporating protective functions that were previously provided by the aircraft or Propeller systems. Examples are reducing the Engine to idle thrust if a thrust reverser deploys and providing the auto-feather function for the Propeller when an Engine fails.

The reliability and availability associated with these functions should be consistent with the top level hazard assessment of conditions involving these functions. This will be completed during aircraft certification.

For example, if an Engine Failure with loss of the auto-feather function is catastrophic at the aircraft level - and the auto-feather function is incorporated into the Engine Control System - the applicant will have to show for CS-25 installations (or CS-23 installations certified to CS-25 specifications) that an Engine Failure with loss of the auto-feather function cannot result from a single control system Failure, and that combinations of control system Failures, or Engine and control system Failures, which lead to a significant Engine loss of thrust or power with an associated loss of the autofeather function may be required to have an extremely improbable event rate (i.e., 10-9 events per Engine flight hour).

Although these functions await evaluation at the aircraft level, it is strongly recommended that, if practicable, the aircraft level hazard assessment involving these functions be available at the time of the Engine Control System certification. This will facilitate discussions and co-ordination between the Engine and aircraft certification teams under the conditions outlined in paragraph (15) of this AMC. It is recognised that this co-ordination may not occur for various reasons. Because of this, the applicant should recognise that although the Engine may be certified, it may not be installable at the aircraft level.

The overall requirement is that the safety assessment of the Engine Control System should include all Failure modes of all functions incorporated in the system. This includes those functions which are added to support aircraft certification, so that the information of those Failure modes will get properly addressed and passed on to the installer for inclusion in the airframe SSA. Information concerning the frequencies of occurrence of those Failure modes may be needed as well.

(10) SOFTWARE AND AIRBORNE ELECTRONIC HARDWARE (AEH)DESIGN AND IMPLEMENTATION

(a) Objective

For Engine Control Systems that use software/AEH, the objective of CS-E 50(f) is to prevent as far as possible software/AEH errors that would result in an unacceptable effect on power or thrust, or any unsafe condition.

In multiple Engine installations, the possibility of software/AEH errors that are common to more than one Engine Control System may determine the criticality level of the software/AEH.

(b) Approved Methods

Methods for developing software/AEH that are compliant with the guidelines contained in the latest edition of [AMC 20-115](#_DxCrossRefBm1701657978)/[AMC 20-152](#_DxCrossRefBm1701657977) are acceptable methods. Alternative methods for developing software/AEH may be proposed by the applicant and are subject to approval by EASA.

Software/AEH which was not developed using the versions of ED-12/ED-80 referenced in the latest edition of [AMC 20-115](#_DxCrossRefBm1701657978)/[AMC 20-152](#_DxCrossRefBm1701657977) is referred to as legacy software/AEH. In general, changes made to legacy software/AEH applicable to its original installation are assured in the same manner as the original certification. When legacy software/AEH is used in a new aircraft installation that requires the latest edition of [AMC 20‑115](#_DxCrossRefBm1701657978)/[AMC 20‑152](#_DxCrossRefBm1701657977), the original approval of the legacy software/AEH is still valid, assuming equivalence to the required software/AEHcriticalitylevel can be ascertained. If the software/AEH development method equivalence is acceptable to EASA, taking into account the conditions defined in the latest edition of [AMC 20-115](#_DxCrossRefBm1701657978)/[AMC 20-152](#_DxCrossRefBm1701657977), the legacy software/AEH can be used in the new installation. If equivalence cannot be substantiated, all the software changes should be assured through the use of the latest edition of [AMC 20-115](#_DxCrossRefBm1701657978) for software or of [AMC 20-152](#_DxCrossRefBm1701657977) for AEH.

Note: In this AMC, the ‘criticality level’ is used to reflect either the software level of a software item or the AEH design assurance level (or DAL) of an AEH item.

The software/AEH criticality level is determined by the Engine safety assessment process. ED-79A/ARP4754A and ARP4761 provide guidelines on how to conduct an aircraft/Engine/system safety assessment process. The Engine software/AEH should be developed at the criticality levels that have been determined and agreed by the Engine and aircraft applicants. It is assumed that by this agreement, the aircraft certification specifications are met.

Determination of the appropriate software/AEH criticality level may depend on the Failure modes and consequences of those Failures. For example, it is possible that Failures resulting in significant thrust or power increases or oscillations may be more severe than an Engine shutdown and, therefore, the possibility of these types of Failures should be considered when selecting a given software/AEH criticality level.

(d) On-Board or Field Software Loading and Part Number Marking

The following guidelines should be followed when on-board or field loading of Electronic Engine Control software and associated Electronic Part Marking (EPM) is implemented.

For software changes, the software to be loaded should have been documented by an approved design change and released with a service bulletin.

For an EECS unit having separate part numbers for hardware and software, the software part number(s) need not be displayed on the unit as long as the software part number(s) is(are) embedded in the loaded software and can be verified by electronic means. When new software is loaded into the unit, the same verification requirement applies and the proper software part number should be verified before the unit is returned to service.

For an EECS unit having only one part number, which represents a combination of a software and hardware build, the unit part number on the nameplate should be changed or updated when the new software is loaded. The software build or version number should be verified before the unit is returned to service.

The configuration control system for an EECS that will be onboard/field loaded and using electronic part marking should be approved. The drawing system should provide a compatibility table that tabulates the combinations of hardware part numbers and software versions that have been approved by the Agency. The top-level compatibility table should be under configuration control, and it should be updated for each change that affects hardware/software combinations. The applicable service bulletin should define the hardware configurations with which the new software version is compatible.

The loading system should be in compliance with the guidelines of the latest edition of [AMC 20-115](#_DxCrossRefBm1701657978).

If the applicant proposes more than one source for loading, (e.g., diskette, mass storage, Secure Disk card, USB stick flash, etc.), all sources should comply with these guidelines.

The service bulletin should require verification that the correct software version has been loaded after installation on the aircraft.

(e) Software Change Category

The processes and methods used to change software should not affect the software level of that software. For classification of software changes, refer to §4 in Appendix A of GM 21.A.91.

(f) Software Changes by Others than the TC Holder

There are two types of potential software changes that could be implemented by someone other than the original TC holder:

— option-selectable software, or

— user-modifiable software (UMS).

Option-selectable changes would have to be pre-certified utilising a method of selection which has been shown not to be capable of causing a control malfunction.

UMS is software intended for modification by the aircraft operator without review by the certification authority, the aircraft applicant, or the equipment vendor. For Engine Control Systems, UMS has generally not been applicable. However, approval of UMS, if required, would be addressed on a case-by-case basis.

In principle, persons other than the TC holder may modify the software within the modification constraints defined by the TC holder, if the system has been certified with the provision for software user modifications. To certify an Electronic Engine Control System with the provision for software modification by others than the TC holder, the TC holder should (1) provide the necessary information for approval of the design and implementation of a software change, and (2) demonstrate that the necessary precautions have been taken to prevent the user modification from affecting Engine airworthiness, especially if the user modification is incorrectly implemented.

In the case where the software is changed in a manner not pre-allowed by the TC holder as “user modifiable”, the “non-TC holder” applicant will have to comply with the requirements given in Part 21, subpart E.

(11) RESERVED

(12) AIRCRAFT-SUPPLIED DATA

(a) Objective

As required by CS-E 50(g), in case of loss, interruption, or corruption of Aircraft-Supplied Data, the Engine should continue to function in a safe and acceptable manner, without unacceptable effects on thrust or power, Hazardous Engine Effects, or loss of ability to comply with the operating specifications of CS-E 390, CS-E 500(a) and CS-E 745, as appropriate.

(b) Background

Historically, regulatory practice was to preserve the Engine independence from the aircraft. Hence even with very reliable architecture, such as triply redundant air data computer (ADC) systems, it was required that the Engine Control System provided an independent control means that could be used to safely fly the aircraft should all the ADC signals be lost.

However, with the increased Engine-aircraft integration that is currently occurring in the aviation industry and with the improvement in reliability and implementation of Aircraft-Supplied Data, the regulatory intent is being revised to require that Fault Accommodation be provided against single Failures of Aircraft-Supplied Data. This may include Fault Accommodation by transition into another Control Mode that is independent of Aircraft-Supplied Data.

The Engine Control System’s LOTC/LOPC analysis should contain the effects of air data system Failures in all allowable Engine Control System and air data system dispatch configurations.

When Aircraft-Supplied Data can affect Engine Control System operation, the applicant should address the following items, as applicable, in the SSA or other appropriate documents:

— Software in the data path to the EECS should be at a level consistent with that defined for the EECS. The data path may include other aircraft equipment, such as aircraft thrust management computers, or other avionics equipment.

— The applicant should state in the instructions for installation that the aircraft applicant is responsible for ensuring that changes to aircraft equipment, including software, in the data path to the Engine do not affect the integrity of the data provided to the Engine as defined by the Engine instructions for installation.

— The applicant should supply the effects of faulty and corrupted Aircraft-Supplied Data on the EECS in the Engine instructions for installation.

— The instructions for installation should state that the installer should ensure that those sensors and equipment involved in delivering information to the EECS are capable of operating in the EMI, HIRF and lightning environments, as defined in the certification basis for the aircraft, without affecting their proper and continued operation.

— The applicant should state the reliability level for the Aircraft-Supplied Data that was used as part of the SSA and LOTC/LOPC analysis as an “assumed value” in the instructions for installation.

As stated in CS-E 50(g), thrust and power command signals sent from the aircraft are not subject to the specifications of CS-E 50(g)(2). If the aircraft thrust or power command system is configured to move the Engine thrust or power levers or transmit an electronic signal to command a thrust or power change, the Engine Control System merely responds to the command and changes Engine thrust or power as appropriate. The Engine Control System may have no way of knowing that the sensed throttle or power lever movement was correct or erroneous.

In both the moving throttle (or power lever) and non-moving throttle (or power lever) configurations, it is the installer’s responsibility to show that a proper functional hazard analysis is performed on the aircraft system involved in generating Engine thrust or power commands, and that the system meets the appropriate aircraft’s functional hazard assessment safety related specifications. This task is an aircraft certification issue, however Failures of the system should be included in the Engine’s LOTC/LOPC analysis.

The applicant should prepare a Fault Accommodation chart that defines the Fault Accommodation architecture for the Aircraft-Supplied Data.

There may be elements of the Engine Control System that are mounted in the aircraft and are not part of the Engine type design, but which are dedicated to the Engine Control System and powered by it, such as a throttle position resolver. In these instances, such elements are considered to be an integral component of the Electronic Engine Control System and are not considered aircraft data.

In the case where the particular Failure modes of the aircraft air data may be unknown, the typical Failure modes of loss of data and erroneous data should be assumed. The term “erroneous data” is used herein to describe a condition where the data appears to be valid but is incorrect.

Such assumptions and the results of the evaluation of erroneous aircraft data should be provided to the installer.

The following are examples of possible means of accommodation:

— Provision of an Alternate Mode that is independent of Aircraft-Supplied Data.

— Dual sources of aircraft-supplied sensor data with local Engine sensors provided as voters and alternate data sources.

— Use of synthesised Engine parameters to control or as voters. When synthesised parameters are used for control or voting purposes, the analysis should consider the impact of temperature and other environmental effects on those sensors whose data are used in the synthesis. The variability of any data or information necessary to relate the data from the sensors used in the synthesis to the parameters being synthesised should also be assessed.

— Triple redundant ADC systems that provide the required data.

If for aircraft certification it is intended to show that the complete loss of the aircraft air data system itself is extremely improbable, then it should be shown that the aircraft air data system is unaffected by a complete loss of aircraft generated power, for example, backed up by battery power. (See [AMC 20-1](#_DxCrossRefBm1701657975))

(d) Effects on the Engine

CS-E 510 defines the Hazardous Engine Effects for turbine Engines.

CS-E 50(g) is primarily intended to address the effects of aircraft signals, such as aircraft air data information, or other signals which could be common to all Engine Control Systems in a multi-Engine installation. The control system design should ensure that the full-up system is capable of providing the declared minimum rated thrust or power throughout the Engine operating envelope.

CS-E 50(g) requires the applicant to provide an analysis of the effect of loss or corruption of aircraft data on Engine thrust or power. The effects of Failures in Aircraft-Supplied Data should be documented in the SSA as described in Section (8) above. Where appropriate, aircraft data Failures or malfunctions that contribute to LOTC/LOPC events should be included in the LOTC/LOPC analysis.

(e) Validation

Functionality of the Fault Accommodation logic should be demonstrated by test, analysis, or combination thereof. In the case where the aircraft air data system is not functional because of the loss of all aircraft generated power, the Engine Control System should include validated Fault Accommodation logic which allows the Engine to operate acceptably with the loss of all aircraft-supplied air data. Engine operation in this system configuration should be demonstrated by test.

For all dispatchable Control Modes, see CS-E 1030 and AMC E 1030.

If an Alternate Mode, independent of Aircraft-Supplied Data, has been provided to accommodate the loss of all data, sufficient testing should be conducted to demonstrate that the operability specifications have been met when operating in this mode. Characteristics of operation in this mode should be included in the instructions for installation and operation as appropriate. This Alternate Mode need not be dispatchable.

(13) AIRCRAFT SUPPLIED ELECTRICAL POWER

(a) Objective

The objective is to provide an electrical power source that is single Fault tolerant (including common cause or mode) in order to allow the EECS to comply with CS-E 50(c)(2). The most common practice for achieving this objective has been to provide a dedicated electrical power source for the EECS. When aircraft electrical power is used, the assumed quality and reliability levels of this aircraft power should be contained in the instructions for installation.

(b) Electrical power sources

An Engine dedicated power source is defined herein as an electric power source providing electrical power generated and supplied solely for use by a single Engine Control System. Such a source is usually provided by an alternator(s), mechanically driven by the Engine or the transmission system of rotorcraft. However, with the increased integration of the Engine-aircraft systems and with the application of EECS to small Engines, both piston and turbine, use of an Engine-mounted alternator may not necessarily be the only design approach for meeting the objective.

Batteries are considered an Aircraft-Supplied Power source except in the case of piston Engines. For piston Engines, a battery source dedicated solely to the Engine Control System may be accepted as an Engine dedicated power source. In such applications, appropriate information for the installer should be provided including, for example, health status and maintenance requirements for the dedicated battery system.

An analysis and a review of the design architecture should identify the requirements for Engine dedicated power sources and Aircraft-Supplied Power sources. The analysis should include the effects of losing these sources. If the Engine is dependent on Aircraft-Supplied Power for any operational functions, the analysis should result in a definition of the requirements for Aircraft-Supplied Power.

The following configurations have been used:

— EECS dependent on Aircraft-Supplied Power

— EECS independent of Aircraft-Supplied Power (Engine dedicated power source)

— Aircraft-Supplied Power used for functions, switched by the EECS

— Aircraft-Supplied Power directly used for Engine functions, independently from the EECS

— Aircraft-Supplied Power used to back up the Engine dedicated power source

The capacity of any Engine dedicated power source, required to comply with CS-E 50(h)(2), should provide sufficient margin to maintain confidence that the Engine Control System will continue to function in all anticipated Engine operating conditions where the control system is designed and expected to recover Engine operation automatically in-flight. The autonomy of the Engine Control System should be sufficient to ensure its functioning in the case of immediate automatic relight after unintended shutdown. Conversely, the autonomy of the Engine Control System in the whole envelope of restart in windmilling conditions is not always required. This margin should account for any other anticipated variations in the output of the dedicated power source such as those due to temperature variations, manufacturing tolerances and idle speed variations. The design margin should be substantiated by test and/or analysis and should also take into account any deterioration over the life of the Engine.

(d) Aircraft-Supplied Power Reliability

Any Aircraft-Supplied Power reliability values used in system analyses, whether supplied by the aircraft manufacturer or assumed, should be contained in the instructions for installation.

When Aircraft-Supplied Power is used in any architecture, if aircraft power Faults or Failures can contribute to LOTC/LOPC or Hazardous Engine Effects, these events should be included in the Engine SSA and LOTC/LOPC analyses.

When compliance with CS-E 50(h)(1) imposes an Engine dedicated power source, Failure of this source should be addressed in the LOTC/LOPC analysis required under CS-E 50 (c). While no credit is normally necessary to be given in the LOTC/LOPC analysis for the use of Aircraft-Supplied Power as a back-up power source, Aircraft-Supplied Power has typically been provided for the purpose of accommodating the loss of the Engine dedicated power source. However, LOTC/LOPC allowance and any impact on the SSA for the use of Aircraft-Supplied Power as the sole power source for an Engine control Back-up System or as a back-up power source would be reviewed on a case-by-case basis.

In some system architectures, an Engine dedicated power source may not be required and Aircraft-Supplied Power may be acceptable as the sole source of power.

An example is a system that consists of a primary electronic single channel and a full capability hydromechanical Back-up System that is independent of electrical power (a full capability hydromechanical control system is one that meets all CS-E specifications and is not dependent on aircraft power). In this type of architecture, loss or interruption of Aircraft-Supplied Power is accommodated by transferring control to the hydromechanical system. Transition from the electronic to the hydromechanical control system is addressed under CS-E 50(b).

Another example is an EECS powered by an aircraft power system that could support a critical fly-by-wire flight control system. Such a power system may be acceptable as the sole source of power for an EECS. In this example, it should be stated in the instructions for installation that a detailed design review and safety analysis is to be conducted to identify latent failures and common cause failures that could result in the loss of all electrical power. The instructions should also state that any emergency power sources must be known to be operational at the beginning of the flight. Any emergency power sources must be isolated from the normal electrical power system in such a way that the emergency power system will be available no matter what happens to the normal generated power system. If batteries are the source of emergency power, there must be a means of determining their condition prior to flight, and their capacity must be shown to be sufficient to assure exhaustion will not occur before getting the aircraft safely back on the ground.

This will satisfy that appropriate reliability assumptions are provided to the installer.

(e) Aircraft-Supplied Power Quality

When Aircraft-Supplied Power is necessary for operation of the Engine Control System, CS-E 50(h)(3) specifies that the Engine instructions for installation contain the Engine Control System’s electrical power supply quality requirements. This applies to any of the configurations listed in paragraph (13)(c) or any new configurations or novel approach not listed that use Aircraft-Supplied Power. These quality requirements should include steady state and transient under-voltage and over-voltage limits for the equipment. The power input standards of RTCA DO-160/EUROCAE ED-14 are considered to provide an acceptable definition of such requirements. If RTCA DO-160/EUROCAE ED-14 is used, any exceptions to the power quality standards cited for the particular category of equipment specified should be stated.

It is recognised that the electrical or electronic components of the Engine Control System when operated on Aircraft-Supplied Power may cease to operate during some low voltage aircraft power supply conditions beyond those required to sustain normal operation, but in no case should the operation of the Engine control result in a Hazardous Engine Effect. In addition, low voltage transients outside the control system’s declared capability should not cause permanent loss of function of the control system, or result in inappropriate control system operation which could cause the Engine to exceed any operational limits, or cause the transmission of unacceptable erroneous data.

When aircraft power recovers from a low-voltage condition to a condition within which the control system is expected to operate normally, the Engine Control System should resume normal operation. The time interval associated with this recovery should be contained in the Engine instructions for installation. It is recognised that Aircraft-Supplied Power conditions may lead to an Engine shutdown or Engine condition which is not recoverable automatically. In these cases the Engine should be capable of being restarted, and any special flight crew procedures for executing an Engine restart during such conditions should be contained in the Engine instructions for operation. The acceptability of any non-recoverable Engine operating conditions - as a result of these Aircraft-Supplied Power conditions - will be determined at aircraft certification.

If Aircraft-Supplied Power supplied by a battery is required to meet an "all Engines out" restart requirement, the analysis according to paragraph 13(c) should result in a definition of the requirements for this Aircraft-Supplied Power. In any installation where aircraft electrical power is used to operate the Engine Control System, such as low Engine speed in-flight re-starting conditions, the effects of any aircraft electrical bus-switching transients or power transients associated with application of electrical loads, which could cause an interruption in voltage or a decay in voltage below that level required for proper control functioning, should be considered.

(f) Effects on the Engine

Where loss of aircraft power results in a change in Engine Control Mode, the Control Mode transition should meet the specifications of CS-E 50(b).

For some Engine control functions that rely exclusively upon Aircraft-Supplied Power, the loss of electrical power may still be acceptable. Acceptability is based on evaluation of the change in Engine operating characteristics, experience with similar designs, or the accommodation designed into the control system.

Examples of such Engine control functions that have traditionally been reliant on aircraft power include:

— Engine start and ignition

— Thrust Reverser deployment

— Anti-Icing (Engine probe heat)

— Fuel Shut-Off

— Over-speed Protection Systems

— Non-critical functions that are primarily performance enhancement functions which, if inoperative, do not affect the safe operation of the Engine.

(g) Validation

The applicant should demonstrate the effects of loss of Aircraft-Supplied Power by Engine test, system validation test or bench test or combination thereof.

(14) PISTON ENGINES

Piston Engines are addressed by the sections above; no additional specific guidance is necessary.

CS-E 50 specifications are applicable to these Engines but, when interpretation is necessary, the conditions which would be acceptable for the aircraft installation should be considered.

(15) ENGINE, PROPELLER AND AIRCRAFT SYSTEMS INTEGRATION AND THE INTERRELATION BETWEEN ENGINE, PROPELLER AND AIRCRAFT CERTIFICATION ACTIVITIES

(a) Aircraft or Propeller Functions Integrated into the Engine Control System

This involves the integration of aircraft or Propeller functions (i.e., those that have traditionally not been considered Engine control functions), into the Electronic Engine Control System’s hardware and software.

Examples of this include thrust reverser control systems, Propeller speed governors, which govern speed by varying pitch, and ATTCS. When this type of integration activity is pursued, the EECS becomes part of - and should be included in the aircraft’s SSA, and although the aircraft functions incorporated into the EECS may receive review at Engine certification, the acceptability of the safety analysis involving these functions should be determined at aircraft certification.

The EECS may be configured to contain only part of the aircraft system’s functionality, or it may contain virtually all of it. Thrust reverser control systems are an example where only part of the functionality is included in the EECS. In such cases, the aircraft is configured to have separate switches and logic (i.e., independent from the EECS) as part of the thrust reverser control system. This separation of reverser control system elements and logic provides an architectural means to limit the criticality of the functions provided by the EECS.

However, in some cases the EECS may be configured to incorporate virtually all of a critical aircraft function. Examples of this “virtual completeness” in aircraft functionality are EECS which contain full authority to govern Propeller speed in turboprop powered aircraft and ATTCS in turbofan power aircraft.

The first of these examples is considered critical because, if an Engine fails, the logic in the Engine Control System should be configured to feather the Propeller on that Engine. Failure to rapidly feather the Propeller following an Engine Failure results in excessive drag on the aircraft, and such a condition can be critical to the aircraft. When functions like these are integrated into the Engine control such that they render an EECS critical, special attention should be paid to assuring that no single (including common cause/mode) Failures could cause the critical Failure condition, e.g. exposure of the EECS to overheat should not cause both an Engine shutdown and Failure of the Propeller to feather.

The second example, that of an ATTCS, is considered critical because the system is required to increase the thrust of the remaining Engine(s) following an Engine Failure during takeoff, and the increased thrust on the remaining Engines is necessary to achieve the required aircraft performance.

All of the above examples of integration involve aircraft functionality that would receive significant review during aircraft certification.

(b) Integration of Engine Control Functions into Aircraft Systems

The trend toward systems integration may lead to aircraft systems performing functions traditionally considered part of the Engine Control System. Some designs may use aircraft systems to implement a significant number of the Engine Control System functions. An example would be the complex integrated flight and Engine Control Systems – integrated in aircraft avionics units - which govern Engine speed, rotor speed, rotor pitch angle and rotor tilt angle in tilt-rotor aircraft.

In these designs, aircraft systems may be required to be used during Engine certification. In such cases, the Engine applicant is responsible for specifying the requirements for the EECS in the instructions for installation and substantiating the adequacy of those requirements.

An example of limited integration would be an Engine control which receives a torque output demand signal from the aircraft and responds by changing the Engine’s fuel flow and other variables to meet that demand. However, the EECS itself, which is part of the type design, provides all the functionality required to safely operate the Engine in accordance with CS-E or other applicable specifications.

(i) Objective

To satisfy the aircraft specifications, such as CS 25.901, CS 25.903 and CS 25.1309, an analysis of the consequences of Failures of the Engine Control System on the aircraft has to be made. The Engine applicant should, together with the aircraft applicant, ensure that the software/AEH criticality levels and the safety and reliability objectives for the Engine electronic control system are consistent with these specifications.

(ii) Interface Definition and System Responsibilities

System responsibilities as well as interface definitions should be identified for the functional as well as hardware and software aspects between the Engine, Propeller and the aircraft systems in the appropriate documents.

The Engine/Propeller/aircraft documents should cover in particular:

— Functional requirements and criticality (which may be based on Engine, Propeller and aircraft considerations);

— Fault Accommodation strategies;

— Maintenance strategies;

— The software/AEH criticality level (per function if necessary);

— The reliability objectives for:

— LOTC/LOPC events,

— Transmission of faulty parameters;

— The environmental requirements including the degree of protection against lightning or other electromagnetic effects (e.g. level of induced voltages that can be supported at the interfaces);

— Engine, Propeller and aircraft interface data and characteristics;

— Aircraft power supply requirements and characteristics (if relevant).

(iii) Distribution of Compliance Tasks

The tasks for the certification of the aircraft propulsion system equipped with Electronic Engine Control Systems (EECSs) may be shared between the Engine, Propeller and aircraft applicants. The distribution of these tasks between the applicants should be identified and agreed with the appropriate Engine, Propeller and aircraft authorities. For further information refer to [AMC 20-1()](#_DxCrossRefBm1701657975).

The aircraft certification should deal with the overall integration of the Engine and Propeller in compliance with the applicable aircraft specifications.

The Engine certification will address the functional aspects of the Engine Control System in compliance with the applicable Engine specifications.

Appropriate evidence provided for Engine certification should be used for aircraft certification. For example, the quality of any aircraft function software/AEH and aircraft–Engine interface logic already demonstrated for Engine certification should need no additional substantiation for aircraft certification.

Two examples are given below to illustrate this principle.

(A) Case of an EECS performing the functions for the control of the Engine and the functions for the control of the Propeller.

The Engine certification would address all general requirements such as software/AEH development assurance procedures, EMI, HIRF and lightning protection levels, effects of loss of aircraft-supplied power.

The Engine certification would address the functional aspects for the Engine functions (safety analysis, rate of LOTC/LOPC events, effect of loss of aircraft-supplied data, etc.). The Fault Accommodation logic affecting the control of the Engine, for example, will be reviewed at that time.

The Propeller certification will similarly address the functional aspects for the Propeller functions. The Fault Accommodation logic affecting the control of the Propeller, for example, will be reviewed at that time.

In this example, the Propeller functions and characteristics defined by the Propeller applicant, which are to be provided by the Engine Control System, would normally need to be refined by flight test. The Propeller applicant is responsible for ensuring that these functions and characteristics, which are provided for use during the Engine certification programme, define an airworthy Propeller configuration, even if they have not yet been refined by flight test.

With regard to changes in design, agreement by all parties involved should be reached so that changes to the Engine Control System that affect the Propeller system, or vice versa, do not lead to any inadvertent effects on the other system.

(B) Case of an aircraft computer performing the functions for the control of the Engine.

The aircraft certification will address all general requirements such as software/AEH development assurance procedures, EMI, HIRF and lightning protection levels.

The aircraft certification will address the functional aspects for the aircraft functions.

The Engine certification will address the functional aspects for the Engine functions (safety analysis, rate of LOTC/LOPC events, effect of loss of aircraft-supplied data, etc.) The Fault Accommodation logic affecting the control of the Engine, for example, will be reviewed at that time.

[Amdt 20/2]

[Amdt 20/10]

[Amdt 20/19]

AMC 20-3B Certification of Engines Equipped with Electronic Engine
Control Systems

ED Decision 2020/010/R

(1)       PURPOSE

The existing certification specifications of
CS-E for Engine certification may require specific interpretation for Engines
equipped with Electronic Engine Control Systems (EECS), with special regard to
interface with the certification of the aircraft and/or Propeller when
applicable. Because of the nature of this technology, it has been considered
useful to prepare acceptable means of compliance (AMC) specifically addressing
the certification of these control systems.

Like any AMC, it is issued to outline issues
to be considered during the demonstration of compliance with CS-E.

(2)       SCOPE

This AMC is relevant to Engine certification
specifications for EECS, whether they use electrical or electronic (analogue
or digital) technology. This is in addition to other AMC such as AMC E 50
or AMC E 80.

It gives guidance on the precautions to be
taken for the use of electrical and electronic technology for Engine control,
protection, limiting and monitoring functions, and, where applicable, for the integration
of aircraft or Propeller functions. In the latter case, this document is
applicable to such functions integrated into the EECS, but only to the extent
that these functions affect compliance with CS-E specifications.

The text deals mainly with the thrust and
power functions of an EECS, since this is the prime function of the Engine.
However, there are many other functions, such as bleed valve control, that may
be integrated into the system for operability reasons. The principles outlined
in this AMC apply to the whole EECS.

This document also discusses the division of
compliance tasks for certification between the applicants for Engine,
Propeller (when applicable), and aircraft type certificates. This guidance
relates to issues to be considered during Engine certification. [AMC 20-1()](#_DxCrossRefBm421436781) addresses issues associated
with the Engine installation in the aircraft.

The introduction of electrical and
electronic technology can entail the following:

—
greater dependence of the
Engine on the aircraft owing to the increased use of electrical power or data
supplied from the aircraft;

—
increased integration of
control and related indication functions;

—
increased risk of significant
Failures that are common to more than one Engine of the aircraft which might,
for example, occur as a result of:

—
insufficient protection from
electromagnetic disturbance (e.g. lightning, internal or external radiation
effects) (see CS-E 50(a)(1), CS E-80 and CS-E 170);

—
insufficient integrity of the
aircraft electrical power supply (see CS-E 50(h));

—
insufficient integrity of data
supplied from the aircraft (see CS-E 50(g));

—
hidden design Faults or
discrepancies contained within the design of the propulsion system control
software or airborne electronic hardware (AEH) (see CS-E 50(f)); or

—
omissions or errors in the
system/software/AEH specification (see CS-E 50(f)).

Appropriatedesign and integration
precautions should therefore be taken to minimise any adverse effects from the
above.

(3)       RELEVANT
SPECIFICATIONS AND REFERENCE DOCUMENTS

Although compliance with many CS-E
specifications might be affected by the Engine Control System, the main
paragraphs relevant to the certification of the Engine Control System itself
are the following:

<table border="1" cellpadding="0" cellspacing="0" width="570">
<tr>
<td valign="top" width="348">
CS-E
 Specification
</td>
<td valign="top" width="108">
Turbine
 Engines
</td>
<td valign="top" width="114">
Piston
 Engines
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 20 (Engine configuration and interfaces)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 25 (Instructions for Continued Airworthiness)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 30 (Assumptions)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 50 (Engine Control System)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 60 (Provision for instruments)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 80 (Equipment)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 110 (Drawing and marking of parts — Assembly of parts)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 130 (Fire prevention)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 140 (Tests-Engine configuration)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 170 (Engine systems and component verification)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 210 (Failure analysis)
</td>
<td valign="top" width="108">
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 250 (Fuel System)
</td>
<td valign="top" width="108">
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 390 (Acceleration tests)
</td>
<td valign="top" width="108">
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 500 (Functioning)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E-510
 (Safety analysis)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 560 (Fuel system)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 745 (Engine Acceleration)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 1030 (Time-limited dispatch)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
</table>

The following documents are referenced in AMC
20-3B:

—
International Electrotechnical
Commission (IEC), Central Office, 3, rue de Varembé, P.O. Box 131, CH - 1211
GENEVA 20, Switzerland

—
IEC/PAS 62239, Electronic
Component Management Plans, edition 1.0, dated April 2001

—
IEC/PAS 62240, Use of
Semiconductor Devices Outside Manufacturers’ Specified Temperature Ranges,
edition 1.0, dated April 2001

—
RTCA, Inc. 1828 L Street, NW,
Suite 805, Washington, DC 20036 or EUROCAE, 17, rue Hamelin, 75116 Paris,
France

—
RTCA DO-254/ EUROCAE ED-80,
Design Assurance Guidance for Airborne Electronic Hardware, dated April 19,
2000

—
RTCA DO-160/EUROCAE ED 14,
Environmental Conditions and Test Procedures for Airborne Equipment

—
[AMC 20-115](#_DxCrossRefBm421436784) on software considerations
for certification of airborne systems and equipment

—
Aeronautical Systems Center,
ASC/ENOI, Bldg 560, 2530 Loop Road West, Wright‑Patterson AFB, OH, USA,
45433-7101

—
MIL-STD-461E, Requirements for
the Control of Electromagnetic Interference Characteristics, dated August 20,
1999

—
MIL-STD-810 E or F, Test
Method Standard for Environmental Engineering, E dated July 14, 1989, F dated
January 1, 2000

—
U.S. Department of
Transportation, Subsequent Distribution, Office Ardmore East Business Center,
3341 Q 75th Ave, Landover, MD, USA, 20785

—
AC 20-136, Protection of
Aircraft Electrical/Electronic Systems Against the Indirect Effects of
Lightning, dated March 5, 1990

—
Society of Automotive
Engineers (SAE), 400 Commonwealth Drive, Warrendale, PA 15096-0001 USA or
EUROCAE, 17, rue Hamelin, 75116 Paris, France

—
SAE ARP 5412 / EUROCAE ED-84,
with Amendment 1 & 2, Aircraft Lightning Environment and Related Test
Waveforms, February 2005/May 2001 respectively

—
SAE ARP 5413 / EUROCAE ED-81,
with Amendment 1, Certification of Aircraft Electrical/Electronic Systems for
the Indirect Effects of Lightning, November 1999/August 1999 respectively

—
SAE ARP 5414 / EUROCAE ED-91,
with Amendment 1, Aircraft Lightning Zoning, February 2005/June 1999
respectively

—
SAE ARP 5416 / EUROCAE ED-105,
Aircraft Lightning Test Methods, March 2005/April 2005 respectively

(4)       DEFINITIONS

The words defined in CS-Definitions and in
CS-E 15 are identified by capital letters.

The following figure and associated
definitions are provided to facilitate a clear understanding of the terms used
in this AMC.

![Aviation.Bot AI suggestion, not from EASA source: The image provides a visual representation of definitions related to engine control systems and their associated operational modes, illustrating the relationships between different system types and the modes they enable.

Detailed Description:
The image is titled "DEFINITIONS VISUALISED" at the top center. It is divided conceptually into two main vertical sections: "SYSTEMS" on the left and "MODES" on the right, both underlined.

Under the "SYSTEMS" section, there is a larger conceptual boundary indicated by a thick dashed rectangular outline labeled "ENGINE CONTROL SYSTEM". Inside this boundary, two distinct system components are depicted:
1. **Primary system**: This is represented by a solid-line rectangular box. Inside this box, the text "Primary system" is bolded, followed by two lines of descriptive text: "May be one or more lanes (channels)" and "Lanes typically have equal functionality".
2. **Backup system**: This is represented by a dotted-dashed line rectangular box, positioned below the "Primary system" box. Inside this box, the text "Backup system" is bolded, followed by the descriptive text: "May be hydromechanical control or less capable lane".

Under the "MODES" section, various operational modes are listed:
1. **PRIMARY MODE / NORMAL MODE**: This text appears as a standalone entry.
2. **ALTERNATE MODES**: This is a conceptual boundary indicated by a thick dashed rectangular outline, with the title "ALTERNATE MODES" underlined. Inside this boundary, two specific modes are listed as standalone text entries: "ALTERNATE MODE 1" and "ALTERNATE MODE 2".
3. **BACKUP MODE 1**: This text appears as a standalone entry, positioned below the "ALTERNATE MODES" boundary.
4. **BACKUP MODE 2**: This text appears as a standalone entry, positioned below "BACKUP MODE 1".

Connecting lines with arrows illustrate the relationships between the systems and modes:
* Three solid lines originate from the right side of the "Primary system" box, each terminating with an arrowhead pointing to a mode on the right:
 * One arrow points to "PRIMARY MODE / NORMAL MODE".
 * One arrow points to "ALTERNATE MODE 1".
 * One arrow points to "ALTERNATE MODE 2".
* Two solid lines originate from the right side of the "Backup system" box, each terminating with an arrowhead pointing to a mode on the right:
 * One arrow points to "BACKUP MODE 1".
 * One arrow points to "BACKUP MODE 2".

Contextual Linkage: The diagram visually categorizes the components of an "ENGINE CONTROL SYSTEM" into "Primary system" and "Backup system" and then maps these systems to their corresponding operational "MODES". The "Primary system" is shown to be capable of operating in the "PRIMARY MODE / NORMAL MODE" as well as "ALTERNATE MODE 1" and "ALTERNATE MODE 2". The "Backup system" is shown to be capable of operating in "BACKUP MODE 1" and "BACKUP MODE 2". The dashed and dotted-dashed outlines indicate conceptual groupings or boundaries for the systems and modes.](file_wSyEACTCE2d/image001.jpg)

(5)       GENERAL

It is recognised that the determination of
compliance of the Engine Control System with the applicable aircraft
certification specifications will only be made during the aircraft certification.

In the case where the installation is
unknown at the time of Engine certification, the applicant for Engine
certification should make reasonable installation and operational assumptions
for the target installation. Any installation limitations or operational
issues will be noted in the instructions for installation or operation, and/or
the Type Certificate Data Sheet (TCDS) (see CS‑E 30 Assumptions).

When possible, early coordination between
the Engine and the aircraft applicants is recommended in association with the
relevant authorities as discussed under Section 15 of this AMC.

(6)       SYSTEM
DESIGN AND VALIDATION

(a)       Control Modes —
General

Under CS-E 50(a), the
applicant should perform all necessary testing and analysis to ensure that all
Control Modes, including those which occur as a result of control Fault
Accommodation strategies, are implemented as required.

The need to provide protective functions,
such as overspeed protection, for all Control Modes, including any Alternate
Modes, should be reviewed under the specifications of CS-E 50(c), (d) and (e),
and CS-E 210 or CS-E 510.

Any limitations on operations in Alternate
Modes should be clearly stated in the Engine instructions for installation and
operation.

Descriptions of the functioning of the
Engine Control System operating in its Primary and any Alternate Modes should
be provided in the Engine instructions for installation and operation.

Analyses and/or testing are necessary to
substantiate that operating in the Alternate Modes has no unacceptable effect
on Engine durability or endurance. Demonstration of the durability and
reliability of the control system in all modes is primarily addressed by the
component testing of CS-E 170. Performing some portion of the Engine
certification testing in the Alternate Mode(s) and during transition between
modes can be used as part of the system validation required under CS-E 50(a).

(i)        Engine Test
Considerations

If the Engine certification tests defined in
CS-E are performed using only the Engine Control System’s Primary Mode in the
Full-up Configuration and if approval for dispatch in the Alternate Mode is
requested by the applicant under CS-E 1030, it should be demonstrated, by
analysis and/or test, that the Engine can meet the defined test-success
criteria when operating in any Alternate Mode that is proposed as a
dispatchable configuration as required by CS-E 1030.

Some capabilities, such as operability,
blade-off, rain, hail, bird ingestion, etc., may be lost in some control modes
that are not dispatchable. These modes do not require engine test
demonstration as long as the installation and operating instructions reflect
this loss of capability.

(ii)       Availability

Availability of any Back-up Mode should be
established by routine testing or monitoring to ensure that the Back-up Mode
will be available when needed. The frequency of establishing its availability
should be documented in the Instructions for Continued Airworthiness (ICA).

(b)       Crew Training Modes

This AMC is not specifically intended to
apply to any crew training modes. These modes are usually installation-, and
possibly operator-, specific and need to be negotiated on a case-by-case
basis. As an example, one common application of crew training modes is for
simulation of the ‘failed-fixed’ mode on a twin-engine rotorcraft. Training
modes should be described in the Engine instructions for installation and
operation as appropriate. Also, precautions should be taken in the design of
the Engine Control System and its crew interfaces to prevent inadvertent entry
into any training modes. Crew training modes, including lock-out systems,
should be assessed as part of the System Safety Analysis (SSA) of CS-E 50(d).

For control configurations which are not
dispatchable, but for which the applicant seeks to take credit in the system Loss
of Thrust (or Power) Control (LOTC/LOPC) analysis, it may be acceptable to
have specific operating limitations. In addition, compliance with CS‑E 50(a)
does not imply strict compliance with the operability specifications of CS-E
390, CS-E 500 and CS-E 745 in these non-dispatchable configurations, if it can
be demonstrated that, in the intended installation, no likely pilot control
system inputs will result in Engine surge, stall, flame-out or unmanageable
delay in power recovery. For example, in a twin-engine rotorcraft, a
rudimentary Backup System may be adequate since frequent and rapid changes in
power setting with the Backup System may not be necessary.

In addition to these operability
considerations, other factors which should be considered in assessing the
acceptability of such reduced-capability Backup Modes include:

—
the installed operating
characteristics of the Back-up Mode and the differences from the Primary Mode;

—
the likely impact of the
Back-up Mode operations on pilot workload, if the aircraft installation is
known;

—        the frequency of
transfer from the Primary Mode to the Back-up Mode (i.e. the reliability of
the Primary Mode);frequencies of transfer of less than 1 per 20 000
engine flight hours have been considered acceptable.

(d)       Control Transitions

The intent of CS-E 50(b) is to ensure that
any control transitions, which occur as a result of Fault Accommodation, occur
in an acceptable manner.

In general, transition to Alternate Modes
should be accomplished automatically by the Engine Control System. However,
systems for which pilot action is required to engage the Backup Mode may also
be acceptable. For instance, a Fault in the Primary System may result in a
‘failed-fixed’ fuel flow and some action is required by the pilot to engage
the Backup System in order to modulate Engine power. Care should be taken to
ensure that any reliance on manual transition is not expected to pose an
unacceptable operating characteristic, unacceptable crew workload or require
exceptional skill.

The transient change in power or thrust
associated with transfer to Alternate Modes should be reviewed for compliance
with CS-E 50(b). If available, input from the installer should be considered.
Although this is not to be considered a complete list, some of the items that
should be considered when reviewing the acceptability of Control Mode
transitions are:

—
The frequency of occurrence of
transfers to any Alternate Mode and the capability of the Alternate Mode.
Computed frequency-of-transfer rates should be supported with data from
endurance or reliability testing, in-service experience on similar equipment,
or other appropriate data.

—
The magnitude of the power,
thrust, rotor or Propeller speed transients.

—
Successful demonstration, by
simulation or other means, of the ability of the Engine Control System to
control the Engine safely during the transition. In some cases, particularly
those involving rotorcraft, it may not be possible to make a determination
that the mode transition provides a safe system based solely on analytical or
simulation data. Therefore, a flight test programme to support this data will
normally be expected.

—
An analysis should be provided
to identify those Faults that cause Control Mode transitions either
automatically or through pilot action.

—
For turboprop or turboshaft
engines, the transition should not result in excessive overspeed or underspeed
of the rotor or Propeller which could cause emergency shutdown, loss of
electrical generator power or the setting-off of warning devices.

The thrust or power change associated with
the transition should be declared in the instructions for installing the
Engine.

(i)        Time Delays

Any observable time delays associated with
Control Mode, channel or system transitions or in re-establishing the pilot’s
ability to modulate Engine thrust or power should be identified in the Engine
instructions for installation and operation (see CS-E 50(b)). These delays
should be assessed during aircraft certification.

(ii)       Annunciation to the
Flight Crew

If annunciation is necessary to comply with
CS-E 50(b)(3), the type of annunciation to the flight crew should be
commensurate with the nature of the transition. For instance, reversion to an
Alternate Mode of control where the transition is automatic and the only
observable changes in operation of the Engine are different thrust control
schedules, would require a very different form of annunciation to that
required if timely action by the pilot is required in order to maintain
control of the aircraft.

The intent and purpose of the cockpit
annunciation should be clearly stated in the Engine instructions for
installation and operation, as appropriate.

(e)       Environmental
conditions

Environmental conditions include electromagnetic
interference (EMI), high-intensity radiated fields (HIRF) and lightning. The
environmental conditions are addressed under CS-E 80 and CS-E 170.
The following provides additional guidance for EMI, HIRF and lightning.

(i)        Declared levels

When the installation is known during the
Engine type-certification programme, the Engine Control System should be
tested at levels that have been determined and agreed by the Engine and
aircraft applicants. It is assumed that, by this agreement, the installation
can meet the aircraft certification specifications. Successful completion of
the testing to the agreed levels would be accepted for Engine type
certification. This, however, may make the possibility of installing the
Engine dependent on a specific aircraft.

If the aircraft installation is not known or
defined at the time of the Engine certification, in order to determine the
levels to be declared for the Engine certification, the Engine applicant may
use the external threat level defined at the aircraft level and use
assumptions on installation attenuation effects.

If none of the options defined above are
available, it is recommended that the procedures and minimum default levels
for HIRF testing should be agreed with EASA.

(ii)       Test procedures

(A)      General

The installed Engine Control System,
including representative
Engine–aircraft interface cables, should be the basis for certification
testing.

EMI test procedures and test levels
conducted in accordance with MIL‑STD‑461 or EUROCAE ED 14/DO-160 have been
considered acceptable.

The applicant should use the HIRF test
guidelines provided in EUROCAE ED 14/RTCA DO-160 or equivalent. However, it
should be recognised that the tests defined in EUROCAE ED 14/RTCA DO-160 are
applicable at a component test level, requiring the applicant to adapt these
test procedures to a system level HIRF test to demonstrate compliance with
CS-E 80 and CS‑E 170.

For lightning tests, the guidelines of SAE
ARP 5412, 5413, 5414 and 5416, and EUROCAE ED 14/RTCA DO-160 would be
applicable.

Pin Injection Tests (PIT) are normally
conducted as component tests on the EECS unit and other system components as
required. PIT levels are selected as appropriate from the tables of EUROCAE ED
14/DO-160.

Environmental tests, such as MIL-STD-810,
may be accepted in lieu of EUROCAE ED-14/DO-160 tests where these tests are
equal to or more rigorous than those defined in EUROCAE ED 14/DO-160.

(B)       Open-loop and Closed-loop Testing

HIRF and lightning tests should be conducted
as system tests on closed-loop or open-loop laboratory set-ups.

The closed-loop set-up is usually provided
with hydraulic pressure to move actuators to close the inner actuating loops.
A simplified Engine simulation may be used to close the outer Engine loop.

Testing should be conducted with the Engine
Control System controlling at the most sensitive operating point, as selected
and detailed in the test plans by the applicant. The system should be exposed
to the HIRF and lightning environmental threats while operating at the
selected condition. There may be a different operating point for HIRF and
lightning environmental threats.

For tests in open- and closed-loop set-ups,
the following factors should also be considered:

—
If a special EECS test
software is used, that software should be developed at the criticality level
determined by the Engine safety assessment process.

—
The Engine Control System
should be tested at the criticality levels that have been determined and
agreed by the Engine and aircraft applicants. It is assumed that by this
agreement, the installation meets the aircraft certification specifications.
In some cases, the application code is modified to include the required test
code features.

—
The system test set-up should
be capable of monitoring both the output signals and the input signals.

—
Anomalies observed during
open-loop testing on inputs or outputs should be duplicated on the Engine
simulation to determine whether the resulting power or thrust perturbations
comply with the pass–fail criteria.

(iii)      Pass–Fail Criteria

The pass–fail criteria of CS-E 170 for HIRF
and lightning should be interpreted as ‘no adverse effect’ on the
functionality of the system.

The following are considered adverse
effects:

—
a greater than 3 % change
of Take-off Power or Thrust for a period of more than 2 seconds;

—
transfers to Alternate
Channels, Backup Systems, or Alternate Modes;

—
component damage;

—
false annunciation to the flight
crew, which could cause unnecessary or inappropriate flight crew action;

—
erroneous operation of protection
systems, such as overspeed or thrust reverser circuits.

AEH or software design changes implemented
after the initial environmental testing should be evaluated for their effects
with respect to the EMI, HIRF and lightning environment.

(iv)      Maintenance Actions

CS-E 25 requires that the applicant prepare
Instructions for Continued Airworthiness (ICA). These include a maintenance
plan. Therefore, for any protection system that is part of the type design of
the Engine Control System and is required by the system to meet the qualified
levels of EMI, HIRF and lightning, a maintenance plan should be provided to
ensure the continued airworthiness for the parts of the installed system which
are supplied by the Engine type-certificate holder.

The maintenance actions to be considered
include periodic inspections or tests for required structural shielding, wire
shields, connectors, and equipment protection components. Inspections or tests
when the part is exposed may also be considered. The applicant should provide
the engineering validation and substantiation of these maintenance actions.

(v)       Time-Limited
Dispatch (TLD) Environmental Tests

Although TLD is only an optional requirement
for certification (see CS-E 1000 and CS-E 1030), EMI, HIRF and lightning tests
for TLD are usually conducted together with tests conducted for certification.
Acceptable means of compliance are provided in AMC E 1030.

(7)       INTEGRITY
OF THE ENGINE CONTROL SYSTEM

(a)       Objective

The intent of CS-E 50(c) is to establish
Engine Control System integrity requirements consistent with operational
requirements of the various installations. (See also paragraph (4) of AMC E
50).

(b)       Definition of an
LOTC/LOPC event

(i)        For turbine Engines
intended for CS-25 installations

An LOTC/LOPC event is defined as an
event where the Engine Control System:

—
has lost the capability of
modulating thrust or power between idle and 90% of maximum rated power or
thrust, or

—
suffers a Fault which results
in a thrust or power oscillation greater than the levels given in paragraph
(7)(c) of this AMC, or

—
has lost the capability to
govern the Engine in a manner which allows compliance with the operability specifications
given in CS-E 500(a) and CS-E 745.

(ii)       For turbine Engines
intended for rotorcraft

An LOPC event is defined as an event where the
Engine Control System:

—
has lost the capability of
modulating power between idle and 90% of maximum rated power at the flight
condition, except OEI power ratings, or

—
suffers a Fault which results
in a power oscillation greater than the levels given in paragraph (7)(c) of
this AMC, or

—
has lost the capability to
govern the Engine in a manner which allows compliance with the operability
specifications given in CS-E 500(a) and CS-E 745, with the exception that the
inability to meet the operability specifications in the Alternate Modes may
not be included as LOPC events.

—
Single Engine rotorcraft will
be required to meet the operability specifications in the Alternate Mode(s),
unless the lack of this capability is demonstrated to be acceptable at the
aircraft level. Engine operability in the Alternate Mode(s) is considered a
necessity if:

—
the control transitions to the
Alternate Mode more frequently than the acceptable LOPC rate, or

—
normal flight crew activity
requires rapid changes in power to safely fly the aircraft.

—
For multi-Engine rotorcraft,
the LOPC definition may not need to include the inability to meet the
operability specifications in the Alternate Mode(s). This may be considered
acceptable because when one Engine control transitions to an Alternate Mode,
which may not have robust operability, that Engine can be left at reasonably
fixed power conditions. The Engine(s) with the normally operating control(s)
can change power – as necessary – to complete aircraft manoeuvres and safely
land the aircraft. Demonstration of the acceptability of this type of
operation may be required at aircraft certification.

(iii)      For turbine Engines
intended for other installations

A
LOTC/LOPC event is defined as an event where the Engine Control System:

—
has lost the capability of
modulating thrust or power between idle and 90% of maximum rated power or
thrust, or

—
suffers a Fault which results
in a thrust or power oscillation that would impact controllability in the
intended installation, or

—
has lost the capability to
govern the Engine in a manner which allows compliance with the operability specifications
given in CS-E 500(a) and CS-E 745, as appropriate.

(iv)      For piston Engines

An
LOPC event is defined as an event where the Engine Control System:

—
has lost the capability of
modulating power between idle and 85% of maximum rated power at all operating
conditions, or

—
suffers a Fault which results
in a power oscillation greater than the levels given in paragraph (7)(c) of
this AMC, or

—        has lost the capability to govern the
Engine in a manner which allows compliance with the operability specifications
given in CS-E 390.

(v)       For engines incorporating functions for Propeller control
integrated in the EECS

The following Faults or Failures should be
considered as additional LOPC events:

—
inability to command a change
in pitch,

—
uncommanded change in pitch,

—        uncontrollable
Propeller torque or speed fluctuation.

Any uncommanded thrust or power oscillations
should be of such a magnitude as not to impact aircraft controllability in the
intended installation. Thrust or power oscillations less than 10% peak to peak
of Take-off Power and/or Thrust have been considered acceptable in some
installations, where the failure affects one engine only. Regardless of the
levels discussed herein, if the flight crew has to shut down an Engine because
of unacceptable thrust or power oscillations caused by the control system, such
an event would be deemed an in-service LOTC/LOPC event.

(d)       Acceptable LOTC/LOPC
rate

The applicant may
propose an LOTC/LOPC rate other than those below. Such a proposal should be
substantiated in relation to the criticality of the Engine and control system
relative to the intended installation. The intent is to show equivalence of
the LOTC/LOPC rate to existing systems in comparable installations.

(i)        For turbine Engines

The EECS should not cause more than one
LOTC/LOPC event per 100 000 engine flight hours.

(ii)       For piston Engines

An LOPC rate of 45 per million engine flight
hours (or 1 per 22,222 engine flight hours) has been shown to represent an
acceptable level for the most complex EECS. As a result of the architectures
used in many of the EECS for these engines, the functions are implemented in
independent system elements. These system elements or sub-systems can be fuel
control, or ignition control, or others. If a system were to contain only one
element such as fuel control, then the appropriate total system level would be
15 LOPC events per million engine flight hours. So the system elements are
then additive up to a max of 45 LOPC events per million hours. For example, an
EEC system comprised of fuel, ignition, and wastegate control functions should
meet a total system reliability of 15+15+15 = 45 LOPC events per million
engine flight hours. This criterion is then applied to the entire system and
not allocated to each of the subsystems. Note that a maximum of 45 LOPC events
per million engine flight hours are allowed, regardless of the number of
subsystems. For example, if the EEC system includes more than three
subsystems, the sum of the LOPC rates for the total system should not exceed
45 LOPC events per million engine flight hours for all of the electrical and
electronic elements.

(e)       LOTC/LOPC Analysis

A system reliability analysis should be
submitted to substantiate the agreed LOTC/LOPC rate for the Engine Control
System. A numerical analysis such as a Markov model analysis, fault tree
analysis or equivalent analytical approach is expected.

The analysis should address all components
in the system that can contribute to LOTC/LOPC events. This includes all
electrical, mechanical, hydromechanical, and pneumatic elements of the Engine
Control System. This LOTC/LOPC analysis should be done in conjunction with the
System Safety Assessment required under CS-E 50(d). Paragraph (8) of this AMC
provides additional guidance material.

The engine fuel pump is generally not
included in the definition of the Engine Control System. It is usually
considered part of the fuel delivery system.

The LOTC/LOPC analysis should include those
sensors or elements which may not be part of the Engine type design, but which
may contribute to LOTC/LOPC events. An example of this is the throttle or
power lever transducer, which is usually supplied by the installer. The
effects of loss, corruption or Failure of Aircraft-Supplied Data should be
included in the Engine Control System’s LOTC/LOPC analysis. The reliability
and interface requirements for these non-Engine type design elements should be
contained in the Engine instructions for installation. It needs to be ensured
that there is no double counting of the rate of Failure of non-engine parts
within the aircraft system safety analyses.

The LOTC/LOPC analysis should consider all
Faults, both detected and undetected. Any periodic maintenance actions needed
to find and repair both Covered and Uncovered Faults, in order to meet the
LOTC/LOPC rate, should be contained in the Engine instructions for continued
airworthiness.

(f)        Commercial or
Industrial Grade Electronic Parts

When the Engine type design specifies
commercial or industrial grade electronic components, which are parts not
manufactured to military standards, the applicant should have the following
data available for review, as applicable:

—
Reliability data that
substantiates the Failure rate for each component used in the LOTC/LOPC
analysis and the SSA for each commercial and industrial grade electrical
component specified in the design.

—
The applicant’s procurement,
quality assurance, and process control plans for the vendor-supplied
commercial and industrial grade parts. These plans should ensure that the
parts will be able to maintain the reliability level specified in the approved
Engine type design.

—
Unique databases for similar
components obtained from different vendors, because commercial and industrial
grade parts may not all be manufactured to the same accepted industry
standard, such as military component standards.

—
Commercial and industrial
grade parts have typical operating ranges of 0 degrees to +70 degrees Celsius
and -40 degrees to +85 degrees Celsius, respectively. Military grade parts are
typically rated at -54 degrees to 125 degrees Celsius. Commercial and industrial
grade parts are typically defined in these temperature ranges in vendor parts
catalogues. If the declared temperature environment for the Engine Control
System exceeds the stated capability of the commercial or industrial grade
electronic components, the applicant should substantiate that the proposed
extended range of the specified components is suitable for the installation
and that the Failure rates used for those components in the SSA and LOTC/LOPC
analyses is appropriately adjusted for the extended temperature environment.
Additionally, if commercial or industrial parts are used in an environment
beyond their specified rating and cooling provisions are required in the
design of the EECS, the applicant should specify these provisions in the instructions
for installation to ensure that the provisions for cooling are not
compromised. Failure modes of the cooling provisions included in the EECS
design that cause these limits to be exceeded should be considered in
determining the probability of Failure.

—
Two examples of industry
published documents which provide guidance on the application of commercial or
industrial grade components are:

—
IEC/PAS 62239, Electronic
Component Management Plans

—
IEC/PAS 62240, Use of
Semiconductor Devices Outside Manufacturers’ Specified Temperature Ranges

When any electrical or electronic components
are changed, the SSA and LOTC/LOPC analyses should be reviewed with regard to
the impact of any changes in component reliability. Component, subassembly or
assembly level testing may be required by the Agency to substantiate a change
that introduces a commercial or industrial part(s). However, such a change
would not be classified as ‘significant’ with respect to Part 21.A.101(b)1.

(g)       Single Fault
Accommodation

Compliance with the single Fault
specifications of CS-E 50(c)(2) and (3) may be substantiated by a combination
of tests and analyses. The intent is that single Failures or malfunctions in
the Engine Control System’s components, in its fully operational condition, do
not result in a Hazardous Engine Effect. In addition, in its full-up
configuration the control system should be essentially single Fault tolerant
of electrical/electronic component Failures with respect to LOTC/LOPC events.
For dispatchable configurations refer to CS-E 1030 and AMC E 1030.

It is recognised that to achieve true single
Fault tolerance for LOTC/LOPC events could require a triplicated design
approach or a design approach with 100% Fault detection. Currently, systems
have been designed with dual, redundant channels or with Back-up Systems that
provide what has been called an "essentially single Fault tolerant"
system. Although these systems may have some Faults that are not Covered
Faults, they have demonstrated excellent in-service safety and reliability, and
have proven to be acceptable.

The objective, of course, is to have all the
Faults addressed as Covered Faults. Indeed, the dual channel or Back-up system
configurations do cover the vast majority of potential electrical and
electronic Faults. However, on a case-by-case basis, it may be appropriate for
the applicant to omit some coverage because detection or accommodation of some
electrical/electronic Faults may not be practical. In these cases, it is
recognised that single, simple electrical or electronic components or circuits
can be employed in a reliable manner, and that requiring redundancy in some
situations may not be appropriate. In these circumstances, Failures in some
single electrical or electronic components, elements or circuits may result in
an LOTC/LOPC event. This is what is meant by the use of the term
“essentially”, and such a system may be acceptable.

(h)       Local Events

Examples of local events to be considered
under CS-E 50(c)(4) include:

—
Overheat conditions, for
example, those resulting from hot air duct bursts,

—
Fires, and

—
Fluid leaks or mechanical
disruptions which could lead to damage to control system electrical harnesses,
connectors, or the control unit(s).

These local events would normally be limited
to one Engine. Therefore, a local event is not usually considered to be a
common mode event, and common mode threats, such as HIRF, lightning and rain,
are not considered local events.

When demonstration that there is no
Hazardous Engine Effect is based on the assumption that another function
exists to afford the necessary protection, it should be shown that this
function is not rendered inoperative by the same local event on the Engine
(including destruction of wires, ducts, power supplies).

It is considered that an overheat condition
exists when the temperature of the system components is greater than the
maximum safe design operating temperature for the components, as declared by
the Engine applicant in the Engine instructions for installation. The Engine
Control System should not cause a Hazardous Engine Effect when the components
or units of the system are exposed to an overheat or over-temperature
condition. Specific design features or analysis methods may be used to show
compliance with respect to the prevention of Hazardous Engine Effects. Where
this is not possible, for example, due to the variability or the complexity of
the Failure sequence, then testing may be required.

The Engine Control System, including the
electrical, electronic and mechanical parts of the system, should comply with
the fire specifications of CS-E 130 and the interpretative material of AMC E
130 is relevant. This rule applies to the elements of the Engine Control
System which are installed in designated fire zones.

There is no probability associated with CS-E
50(c)(4). Hence, all foreseeable local events should be considered. It is
recognised, however, that it is difficult to address all possible local events
in the intended aircraft installation at the time of Engine certification.
Therefore, sound Engineering judgement should be applied in order to identify
the reasonably foreseeable local events. Compliance with this specification
may be shown by considering the end result of the local event on the Engine
Control System. The local events analysed should be well documented to aid in
certification of the Engine installation.

The following guidance applies to Engine
Control System wiring:

—
Each wire or combination of
wires interfacing with the EECS that could be affected by a local event should
be tested or analysed with respect to local events. The assessment should
include opens, shorts to ground and shorts to power (when appropriate) and the
results should show that Faults result in identified responses and do not result
in Hazardous Engine Effects.

—
Engine control unit aircraft
interface wiring should be tested or analysed for shorts to aircraft power,
and these “hot” shorts should result in an identified and non-Hazardous Engine
Effect. Where aircraft interface wiring is involved, the installer should be
informed of the potential effects of interface wiring Faults by means of
information provided in the Engine instructions for installation. It is the
installer’s responsibility to ensure that there are no wiring Faults which
could affect more than one Engine. Where practical, wiring Faults should not
affect more than one channel. Any assumptions made by the Engine applicant
regarding channel separation should be included in the LOTC/LOPC analysis.

—
Where physical separation of
conductors is not practical, co-ordination between the Engine applicant and
the installer should ensure that the potential for common mode Faults between
Engine Control Systems is eliminated, and between channels on one Engine is
minimised.

The applicant should assess by analysis or
test the effects of fluid leaks impinging on components of the Electronic
Engine Control System. Such conditions should not result in a Hazardous Engine
Effect, nor should the fluids be allowed to impinge on circuitry or printed
circuit boards and result in a potential latent Failure condition.

(8)       SYSTEM
SAFETY ASSESSMENT

(a)       Scope of the
assessment

The system safety assessment (SSA) required
under CS-E 50(d) should address all operating modes, and the data used in the
SSA should be substantiated.

The LOTC/LOPC analysis described in Section
7 is a subset of the SSA. The LOTC/LOPC analysis and SSA may be separate or
combined as a single analysis.

The SSA should consider all Faults, both
detected and undetected, and their effects on the Engine Control System and
the Engine itself. The intent is primarily to address the Faults or
malfunctions which only affect one Engine Control System, and therefore only
one Engine. However, Faults or malfunctions in aircraft signals, including
those in a multi-engine installation that could affect more than one Engine,
should also be included in the SSA; these types of Faults are addressed under
CS-E 50(g).

The Engine Control System SSA and LOTC/LOPC
analysis, or combined analyses, should identify the applicable assumptions and
installation requirements and establish any limitations relating to Engine
Control System operation. These assumptions, requirements, and limitations
should be stated in the Engine instructions for installation and operation as
appropriate. If necessary, the limitations should be contained in the
airworthiness limitations section of the instructions for continued airworthiness
in accordance with CS-E 25(b)(1).

The SSA should address all Failure effects
identified under CS-E 510 or CS-E 210, as appropriate. A summary should be
provided, listing the malfunctions or Failures and their effects caused by the
Engine Control System, such as:

—
Failures affecting power or
thrust resulting in LOTC/LOPC events.

—
Failures which result in the
Engine’s inability to meet the operability specifications. If these Failure
cases are not considered as LOPC events according to paragraph (7)(b)(ii) of
this AMC, the expected frequency of occurrence for these events should be
documented.

—
Transmission of erroneous
parameters which could lead to thrust or power changes greater than 3% of
Take-off Power or Thrust (10% for piston engines installations) (e.g., false
high indication of the thrust or power setting parameter) or to Engine
shutdown (e.g., high EGT or turbine temperatures or low oil pressure).

—
Failures affecting functions
included in the Engine Control System, which may be considered aircraft
functions (e.g. Propeller control, thrust reverser control, control of cooling
air, control of fuel recirculation)

—
Failures resulting in Major
Engine Effects and Hazardous Engine Effects.

The SSA should also consider all signals
used by the Engine Control System, in particular any cross-Engine control
signals and air signals as described in CS-E 50(i).

The criticality of functions included in the
Engine Control System for aircraft level functions needs to be defined by the
aircraft applicant.

(b)       Criteria

The SSA should demonstrate or provide the
following:

(i)        Compliance with
CS-E 510 or CS-E 210, as appropriate.

(ii)       For Failures
leading to LOTC/LOPC events,compliance with the agreed LOTC/LOPC rate for the intended
installation (see paragraph (7)(d) of this AMC).

(iii)      For Failures
affecting Engine operability but not leading to LOPC events,compliance with the expected total frequency of occurrence of
Failures that result in Engine response that is non-compliant with CS-E 390,
CS-E 500(a) and CS-E 745 specifications (as appropriate). The acceptability of
the frequency of occurrence for these events - along with any aircraft flight
deck indications deemed necessary to inform the flight crew of such a
condition - will be determined at aircraft certification.

(iv)      The consequence of
the transmission of a faulty parameter

The consequence of the transmission of a
faulty parameter by the Engine Control System should be identified and
included, as appropriate, in the LOTC/LOPC analysis. Any information necessary
to mitigate the consequence of a faulty parameter transmission should be
contained in the Engine operating instructions.

For example, the Engine operating
instructions may indicate that a display of zero oil pressure be ignored
in-flight if the oil quantity and temperature displays appear normal. In this
situation, Failure to transmit oil pressure or transmitting a zero oil
pressure signal should not lead to an Engine shutdown or LOTC/LOPC event.
Admittedly, flight crew initiated shutdowns have occurred in-service during
such conditions. In this regard, if the Engine operating instructions provide
information to mitigate the condition, then control system Faults or
malfunctions leading to the condition do not have to be included in the
LOTC/LOPC analysis. In such a situation, the loss of multiple functions should
be included in the LOTC/LOPC analysis. If the display of zero oil pressure and
zero oil quantity (or high oil temperature) would result in a crew initiated
shutdown, then those conditions should be included in the systems LOTC/LOPC
analysis.

In multi-engine aeroplanes, Faults that
result in thrust or power changes of less than approximately 10% of Take-off
Power or Thrust may be undetectable by the flight crew. This level is based on
pilot assessment and has been in use for a number of years. The pilots
indicated that flight crews will note the Engine operating differences when
the difference is greater than 10% in asymmetric thrust or power.

The detectable difference level for Engines
for other installations should be agreed with the installer.

When operating in the take-off envelope,
Uncovered Faults in the Engine Control System which result in a thrust or
power change of less than 3% (10% for piston engines installations), are
generally considered acceptable. However, this does not detract from the
applicant’s obligation to ensure that the full-up system is capable of
providing the declared minimum rated thrust or power. In this regard, Faults
which could result in small thrust changes should be random in nature and
detectable and correctable during routine inspections, overhauls or
power-checks.

The frequency of occurrence of Uncovered
Faults that result in a thrust or power change greater than 3% of Take-off
Power or Thrust, but less than the change defined as an LOTC/LOPC event,
should be contained in the SSA documentation. There are no firm specifications
relating to this class of Faults for Engine certification; however the rate of
occurrence of these types of Faults should be reasonably low, in the order of
10-4 events per Engine flight hour or less. These Faults may be
required to be included in aircraft certification analysis.

Signals sent from one Engine Control System
to another in an aeroplane installation, such as signals used for an Automatic
Take-off Thrust Control System (ATTCS), synchrophasing, etc., are addressed
under CS-E 50(g). They should be limited in authority by the receiving Engine
Control System, so that undetected Faults do not result in an unacceptable
change in thrust or power on the Engine using those signals. The maximum
thrust or power loss on the Engine using a cross-Engine signal should
generally be limited to 3% absolute difference of the current operating
condition.

Note: It is recognised that ATTCS, when
activated, may command a thrust or power increase of 10% or more on the
remaining Engine(s). It is also recognised that signals sent from one Engine
control to another in a rotorcraft installation, such as load sharing and One
Engine Inoperative (OEI), can have a much greater impact on Engine power when
those signals fail. Data of these Failure modes should be contained in the
SSA.

When operating in the take-off envelope,
detected Faults in the Engine Control System, which result in a thrust or
power change of up to 10% (15% for piston engines) may be acceptable if the
total frequency of occurrence for these types of Failures is relatively low.
The predicted frequency of occurrence for this category of Faults should be
contained in SSA documentation. It should be noted that requirements for the
allowable frequency of occurrence for this category of Faults and any need for
a flight deck indication of these conditions would be reviewed during aircraft
certification. A total frequency of occurrence in excess of 10–4
events per Engine flight hour would not normally be acceptable.

Detected Faults in signals exchanged between
Engine Control Systems should be accommodated so as not to result in greater
than a 3% thrust or power change on the Engine using the cross-Engine signals.

(9)       PROTECTIVE
FUNCTIONS

(a)       Rotor Over-speed
Protection.

Rotor over-speed protection is usually
achieved by providing an independent over-speed protection system, such that
it requires two independent Faults or malfunctions (as described below) to
result in an uncontrolled over-speed.

The following guidance applies if the rotor
over-speed protection is provided solely by an Engine Control System
protective function.

For dispatchable configurations, refer to
CS-E 1030 and AMC E 1030.

The SSA should show that the probability per
Engine flight hour of an uncontrolled over-speed condition from any cause in
combination with a Failure of the over-speed protection system to function is
less than one event per hundred million hours (a Failure rate of 10–8 events
per Engine flight hour).

The over-speed protection system would be
expected to have a Failure rate of less than 10–4 Failures per engine flight
hour to ensure the integrity of the protected function.

A self-test of the over-speed protection
system to ensure its functionality prior to each flight is normally necessary
for achieving the objectives. Verifying the functionality of the over-speed
protection system at Engine shutdown and/or start-up is considered adequate
for compliance with this requirement. It is recognised that some Engines may
routinely not be shut down between flight cycles. In this case this should be
accounted for in the analyses.

Because in some over-speed protection
systems there are multiple protection paths, there will always be uncertainty
that all paths are functional at any given time. Where multiple paths can
invoke the over-speed protection system, a test of a different path may be
performed each Engine cycle. The objective is that a complete test of the
over-speed system, including electro-mechanical parts, is achieved in the
minimum number of Engine cycles. This is acceptable so long as the system
meets a 10-4 Failure rate.

The applicant may provide data that
demonstrates that the mechanical parts (this does not include the
electro-mechanical parts) of the over-speed protection system can operate
without Failure between stated periods, and a periodic inspection may be established
for those parts. This data is acceptable in lieu of testing the mechanical
parts of the sub-system each Engine cycle.

(b)       Other protective
functions

The Engine Control System may perform other
protective functions. Some of these may be Engine functions, but others may be
aircraft or Propeller functions. Engine functions should be considered under
the guidelines of this AMC. The integrity of other protective functions
provided by the Engine Control System should be consistent with a safety
analysis associated with those functions, but if those functions are not
Engine functions, they may not be a part of Engine certification.

As Engine Control Systems become
increasingly integrated into the aircraft and Propeller systems, they are
incorporating protective functions that were previously provided by the
aircraft or Propeller systems. Examples are reducing the Engine to idle thrust
if a thrust reverser deploys and providing the auto-feather function for the
Propeller when an Engine fails.

The reliability and availability associated
with these functions should be consistent with the top level hazard assessment
of conditions involving these functions. This will be completed during
aircraft certification.

For example, if an Engine Failure with loss
of the auto-feather function is catastrophic at the aircraft level - and the
auto-feather function is incorporated into the Engine Control System - the
applicant will have to show for CS-25 installations (or CS-23 installations
certified to CS-25 specifications) that an Engine Failure with loss of the
auto-feather function cannot result from a single control system Failure, and
that combinations of control system Failures, or Engine and control system
Failures, which lead to a significant Engine loss of thrust or power with an
associated loss of the autofeather function may be required to have an
extremely improbable event rate (i.e., 10-9 events per Engine flight hour).

Although these functions await evaluation at
the aircraft level, it is strongly recommended that, if practicable, the
aircraft level hazard assessment involving these functions be available at the
time of the Engine Control System certification. This will facilitate
discussions and co-ordination between the Engine and aircraft certification
teams under the conditions outlined in paragraph (15) of this AMC. It is
recognised that this co-ordination may not occur for various reasons. Because
of this, the applicant should recognise that although the Engine may be
certified, it may not be installable at the aircraft level.

The overall requirement is that the safety
assessment of the Engine Control System should include all Failure modes of
all functions incorporated in the system. This includes those functions which
are added to support aircraft certification, so that the information of those
Failure modes will get properly addressed and passed on to the installer for
inclusion in the airframe SSA. Information concerning the frequencies of
occurrence of those Failure modes may be needed as well.

(10)     SOFTWARE
AND AIRBORNE ELECTRONIC HARDWARE (AEH)DESIGN AND IMPLEMENTATION

(a)       Objective

For Engine Control Systems that use software/AEH,
the objective of CS-E 50(f) is to prevent as far as possible software/AEH
errors that would result in an unacceptable effect on power or thrust, or any
unsafe condition.

In multiple Engine installations, the
possibility of software/AEH errors that are common to more than one Engine
Control System may determine the criticality level of the software/AEH.

(b)       Approved Methods

Methods for developing software/AEH that are
compliant with the guidelines contained in the latest edition of [AMC 20-115](#_DxCrossRefBm421436784)/[AMC 20-152](#_DxCrossRefBm421436783) are acceptable methods.
Alternative methods for developing software/AEH may be proposed by the
applicant and are subject to approval by EASA.

Software/AEH which was not developed using the
versions of ED-12/ED-80 referenced in the latest edition of [AMC 20-115](#_DxCrossRefBm421436784)/[AMC 20-152](#_DxCrossRefBm421436783) is referred to as legacy
software/AEH. In general, changes made to legacy software/AEH applicable to
its original installation are assured in the same manner as the original
certification. When legacy software/AEH is used in a new aircraft installation
that requires the latest edition of [AMC 20‑115](#_DxCrossRefBm421436784)/[AMC 20‑152](#_DxCrossRefBm421436783), the original approval of
the legacy software/AEH is still valid, assuming equivalence to the required
software/AEHcriticalitylevel can be ascertained. If the software/AEH
development method equivalence is acceptable to EASA, taking into account the
conditions defined in the latest edition of [AMC 20-115](#_DxCrossRefBm421436784)/[AMC 20-152](#_DxCrossRefBm421436783), the legacy software/AEH
can be used in the new installation. If equivalence cannot be substantiated,
all the software changes should be assured through the use of the latest
edition of [AMC 20-115](#_DxCrossRefBm421436784) for software
or of [AMC 20-152](#_DxCrossRefBm421436783) for AEH.

Note: In this AMC, the ‘criticality level’
is used to reflect either the software level of a software item or the AEH
design assurance level (or DAL) of an AEH item.

The software/AEH criticality level is
determined by the Engine safety assessment process. ED-79A/ARP4754A and
ARP4761 provide guidelines on how to conduct an aircraft/Engine/system safety
assessment process. The Engine software/AEH should be developed at the
criticality levels that have been determined and agreed by the Engine and
aircraft applicants. It is assumed that by this agreement, the aircraft
certification specifications are met.

Determination of the appropriate software/AEH
criticality level may depend on the Failure modes and consequences of those
Failures. For example, it is possible that Failures resulting in significant
thrust or power increases or oscillations may be more severe than an Engine
shutdown and, therefore, the possibility of these types of Failures should be
considered when selecting a given software/AEH criticality level.

(d)       On-Board or Field
Software Loading and Part Number Marking

The following guidelines should be followed
when on-board or field loading of Electronic Engine Control software and
associated Electronic Part Marking (EPM) is implemented.

For software changes, the software to be
loaded should have been documented by an approved design change and released
with a service bulletin.

For an EECS unit having separate part
numbers for hardware and software, the software part number(s) need not be
displayed on the unit as long as the software part number(s) is(are) embedded
in the loaded software and can be verified by electronic means. When new
software is loaded into the unit, the same verification requirement applies
and the proper software part number should be verified before the unit is
returned to service.

For an EECS unit having only one part
number, which represents a combination of a software and hardware build, the
unit part number on the nameplate should be changed or updated when the new
software is loaded. The software build or version number should be verified
before the unit is returned to service.

The configuration control system for an EECS
that will be onboard/field loaded and using electronic part marking should be
approved. The drawing system should provide a compatibility table that
tabulates the combinations of hardware part numbers and software versions that
have been approved by the Agency. The top-level compatibility table should be
under configuration control, and it should be updated for each change that
affects hardware/software combinations. The applicable service bulletin should
define the hardware configurations with which the new software version is
compatible.

The loading system should be in compliance
with the guidelines of the latest edition of [AMC 20-115](#_DxCrossRefBm421436784).

If the applicant proposes more than one
source for loading, (e.g., diskette, mass storage, Secure Disk card, USB stick
flash, etc.), all sources should comply with these guidelines.

The service bulletin should require
verification that the correct software version has been loaded after
installation on the aircraft.

(e)       Software Change
Category

The processes and methods used to change
software should not affect the software level of that software. For
classification of software changes, refer to §4 in Appendix A of GM 21.A.91.

(f)        Software Changes by
Others than the TC Holder

There are two types of potential software
changes that could be implemented by someone other than the original TC
holder:

—
option-selectable software, or

—
user-modifiable software
(UMS).

Option-selectable changes would have to be
pre-certified utilising a method of selection which has been shown not to be
capable of causing a control malfunction.

UMS is software intended for modification by
the aircraft operator without review by the certification authority, the
aircraft applicant, or the equipment vendor. For Engine Control Systems, UMS
has generally not been applicable. However, approval of UMS, if required,
would be addressed on a case-by-case basis.

In principle, persons other than the TC
holder may modify the software within the modification constraints defined by
the TC holder, if the system has been certified with the provision for
software user modifications. To certify an Electronic Engine Control System
with the provision for software modification by others than the TC holder, the
TC holder should (1) provide the necessary information for approval of the
design and implementation of a software change, and (2) demonstrate that the
necessary precautions have been taken to prevent the user modification from
affecting Engine airworthiness, especially if the user modification is incorrectly
implemented.

In the case where the software is changed in
a manner not pre-allowed by the TC holder as “user modifiable”, the “non-TC
holder” applicant will have to comply with the requirements given in Part 21,
subpart E.

(11)     RESERVED

(12)     AIRCRAFT-SUPPLIED
DATA

(a)       Objective

As required by CS-E 50(g), in case of loss,
interruption, or corruption of Aircraft-Supplied Data, the Engine should
continue to function in a safe and acceptable manner, without unacceptable
effects on thrust or power, Hazardous Engine Effects, or loss of ability to
comply with the operating specifications of CS-E 390, CS-E 500(a) and CS-E
745, as appropriate.

(b)       Background

Historically, regulatory practice was to
preserve the Engine independence from the aircraft. Hence even with very
reliable architecture, such as triply redundant air data computer (ADC)
systems, it was required that the Engine Control System provided an independent
control means that could be used to safely fly the aircraft should all the ADC
signals be lost.

However, with the increased Engine-aircraft
integration that is currently occurring in the aviation industry and with the
improvement in reliability and implementation of Aircraft-Supplied Data, the
regulatory intent is being revised to require that Fault Accommodation be
provided against single Failures of Aircraft-Supplied Data. This may include
Fault Accommodation by transition into another Control Mode that is
independent of Aircraft-Supplied Data.

The Engine Control System’s LOTC/LOPC
analysis should contain the effects of air data system Failures in all
allowable Engine Control System and air data system dispatch configurations.

When Aircraft-Supplied Data can affect
Engine Control System operation, the applicant should address the following
items, as applicable, in the SSA or other appropriate documents:

—
Software in the data path to
the EECS should be at a level consistent with that defined for the EECS. The
data path may include other aircraft equipment, such as aircraft thrust
management computers, or other avionics equipment.

—
The applicant should state in
the instructions for installation that the aircraft applicant is responsible
for ensuring that changes to aircraft equipment, including software, in the
data path to the Engine do not affect the integrity of the data provided to
the Engine as defined by the Engine instructions for installation.

—
The applicant should supply
the effects of faulty and corrupted Aircraft-Supplied Data on the EECS in the
Engine instructions for installation.

—
The instructions for
installation should state that the installer should ensure that those sensors
and equipment involved in delivering information to the EECS are capable of
operating in the EMI, HIRF and lightning environments, as defined in the
certification basis for the aircraft, without affecting their proper and
continued operation.

—
The applicant should state the
reliability level for the Aircraft-Supplied Data that was used as part of the
SSA and LOTC/LOPC analysis as an “assumed value” in the instructions for
installation.

As stated in CS-E 50(g), thrust and power
command signals sent from the aircraft are not subject to the specifications
of CS-E 50(g)(2). If the aircraft thrust or power command system is configured
to move the Engine thrust or power levers or transmit an electronic signal to
command a thrust or power change, the Engine Control System merely responds to
the command and changes Engine thrust or power as appropriate. The Engine
Control System may have no way of knowing that the sensed throttle or power
lever movement was correct or erroneous.

In both the moving throttle (or power lever)
and non-moving throttle (or power lever) configurations, it is the installer’s
responsibility to show that a proper functional hazard analysis is performed
on the aircraft system involved in generating Engine thrust or power commands,
and that the system meets the appropriate aircraft’s functional hazard
assessment safety related specifications. This task is an aircraft
certification issue, however Failures of the system should be included in the
Engine’s LOTC/LOPC analysis.

The applicant should prepare a Fault
Accommodation chart that defines the Fault Accommodation architecture for the
Aircraft-Supplied Data.

There may be elements of the Engine Control
System that are mounted in the aircraft and are not part of the Engine type
design, but which are dedicated to the Engine Control System and powered by
it, such as a throttle position resolver. In these instances, such elements
are considered to be an integral component of the Electronic Engine Control
System and are not considered aircraft data.

In the case where the particular Failure
modes of the aircraft air data may be unknown, the typical Failure modes of
loss of data and erroneous data should be assumed. The term “erroneous data”
is used herein to describe a condition where the data appears to be valid but
is incorrect.

Such assumptions and the results of the
evaluation of erroneous aircraft data should be provided to the installer.

The following are examples of possible means
of accommodation:

—
Provision of an Alternate Mode
that is independent of Aircraft-Supplied Data.

—
Dual sources of
aircraft-supplied sensor data with local Engine sensors provided as voters and
alternate data sources.

—
Use of synthesised Engine
parameters to control or as voters. When synthesised parameters are used for
control or voting purposes, the analysis should consider the impact of
temperature and other environmental effects on those sensors whose data are
used in the synthesis. The variability of any data or information necessary to
relate the data from the sensors used in the synthesis to the parameters being
synthesised should also be assessed.

—
Triple redundant ADC systems
that provide the required data.

If for aircraft certification it is intended
to show that the complete loss of the aircraft air data system itself is
extremely improbable, then it should be shown that the aircraft air data
system is unaffected by a complete loss of aircraft generated power, for
example, backed up by battery power. (See [AMC
20-1](#_DxCrossRefBm421436781))

(d)       Effects on the
Engine

CS-E 510 defines the Hazardous Engine
Effects for turbine Engines.

CS-E 50(g) is primarily intended to address
the effects of aircraft signals, such as aircraft air data information, or
other signals which could be common to all Engine Control Systems in a
multi-Engine installation. The control system design should ensure that the
full-up system is capable of providing the declared minimum rated thrust or
power throughout the Engine operating envelope.

CS-E 50(g) requires the applicant to provide
an analysis of the effect of loss or corruption of aircraft data on Engine
thrust or power. The effects of Failures in Aircraft-Supplied Data should be
documented in the SSA as described in Section (8) above. Where appropriate,
aircraft data Failures or malfunctions that contribute to LOTC/LOPC events
should be included in the LOTC/LOPC analysis.

(e)       Validation

Functionality of the Fault Accommodation
logic should be demonstrated by test, analysis, or combination thereof. In the
case where the aircraft air data system is not functional because of the loss
of all aircraft generated power, the Engine Control System should include
validated Fault Accommodation logic which allows the Engine to operate
acceptably with the loss of all aircraft-supplied air data. Engine operation
in this system configuration should be demonstrated by test.

For all dispatchable Control Modes, see CS-E
1030 and AMC E 1030.

If an Alternate Mode, independent of
Aircraft-Supplied Data, has been provided to accommodate the loss of all data,
sufficient testing should be conducted to demonstrate that the operability
specifications have been met when operating in this mode. Characteristics of
operation in this mode should be included in the instructions for installation
and operation as appropriate. This Alternate Mode need not be dispatchable.

(13)     AIRCRAFT
SUPPLIED ELECTRICAL POWER

(a)       Objective

The objective is to provide
an electrical power source that is single Fault tolerant (including common
cause or mode) in order to allow the EECS to comply with CS-E 50(c)(2). The
most common practice for achieving this objective has been to provide a
dedicated electrical power source for the EECS. When aircraft electrical power
is used, the assumed quality and reliability levels of this aircraft power
should be contained in the instructions for installation.

(b)       Electrical power sources

An Engine dedicated power
source is defined herein as an electric power source providing electrical
power generated and supplied solely for use by a single Engine Control System.
Such a source is usually provided by an alternator(s), mechanically driven by
the Engine or the transmission system of rotorcraft. However, with the
increased integration of the Engine-aircraft systems and with the application
of EECS to small Engines, both piston and turbine, use of an Engine-mounted
alternator may not necessarily be the only design approach for meeting the
objective.

Batteries are considered an
Aircraft-Supplied Power source except in the case of piston Engines. For
piston Engines, a battery source dedicated solely to the Engine Control System
may be accepted as an Engine dedicated power source. In such applications,
appropriate information for the installer should be provided including, for
example, health status and maintenance requirements for the dedicated battery
system.

An analysis and a review of
the design architecture should identify the requirements for Engine dedicated
power sources and Aircraft-Supplied Power sources. The analysis should include
the effects of losing these sources. If the Engine is dependent on Aircraft-Supplied
Power for any operational functions, the analysis should result in a
definition of the requirements for Aircraft-Supplied Power.

The following
configurations have been used:

—
EECS dependent on
Aircraft-Supplied Power

—
EECS independent of Aircraft-Supplied
Power (Engine dedicated power source)

—
Aircraft-Supplied Power used
for functions, switched by the EECS

—
Aircraft-Supplied Power
directly used for Engine functions, independently from the EECS

—
Aircraft-Supplied Power used
to back up the Engine dedicated power source

The capacity of any Engine
dedicated power source, required to comply with CS-E 50(h)(2), should provide
sufficient margin to maintain confidence that the Engine Control System will
continue to function in all anticipated Engine operating conditions where the
control system is designed and expected to recover Engine operation automatically
in-flight. The autonomy of the Engine Control System should be sufficient to
ensure its functioning in the case of immediate automatic relight after
unintended shutdown. Conversely, the autonomy of the Engine Control System in
the whole envelope of restart in windmilling conditions is not always
required. This margin should account for any other anticipated variations in
the output of the dedicated power source such as those due to temperature
variations, manufacturing tolerances and idle speed variations. The design
margin should be substantiated by test and/or analysis and should also take
into account any deterioration over the life of the Engine.

(d)       Aircraft-Supplied Power Reliability

Any Aircraft-Supplied Power
reliability values used in system analyses, whether supplied by the aircraft
manufacturer or assumed, should be contained in the instructions for
installation.

When Aircraft-Supplied
Power is used in any architecture, if aircraft power Faults or Failures can
contribute to LOTC/LOPC or Hazardous Engine Effects, these events should be
included in the Engine SSA and LOTC/LOPC analyses.

When compliance with CS-E
50(h)(1) imposes an Engine dedicated power source, Failure of this source
should be addressed in the LOTC/LOPC analysis required under CS-E 50 (c).
While no credit is normally necessary to be given in the LOTC/LOPC analysis
for the use of Aircraft-Supplied Power as a back-up power source,
Aircraft-Supplied Power has typically been provided for the purpose of
accommodating the loss of the Engine dedicated power source. However,
LOTC/LOPC allowance and any impact on the SSA for the use of Aircraft-Supplied
Power as the sole power source for an Engine control Back-up System or as a
back-up power source would be reviewed on a case-by-case basis.

In some system
architectures, an Engine dedicated power source may not be required and
Aircraft-Supplied Power may be acceptable as the sole source of power.

An example is a system that
consists of a primary electronic single channel and a full capability
hydromechanical Back-up System that is independent of electrical power (a full
capability hydromechanical control system is one that meets all CS-E specifications
and is not dependent on aircraft power). In this type of architecture, loss or
interruption of Aircraft-Supplied Power is accommodated by transferring
control to the hydromechanical system. Transition from the electronic to the
hydromechanical control system is addressed under CS-E 50(b).

Another example is an EECS
powered by an aircraft power system that could support a critical fly-by-wire
flight control system. Such a power system may be acceptable as the sole
source of power for an EECS. In this example, it should be stated in the instructions
for installation that a detailed design review and safety analysis is to be
conducted to identify latent failures and common cause failures that could
result in the loss of all electrical power. The instructions should also state
that any emergency power sources must be known to be operational at the
beginning of the flight. Any emergency power sources must be isolated from the
normal electrical power system in such a way that the emergency power system
will be available no matter what happens to the normal generated power system.
If batteries are the source of emergency power, there must be a means of
determining their condition prior to flight, and their capacity must be shown
to be sufficient to assure exhaustion will not occur before getting the aircraft
safely back on the ground.

This will satisfy that
appropriate reliability assumptions are provided to the installer.

(e)       Aircraft-Supplied Power Quality

When Aircraft-Supplied
Power is necessary for operation of the Engine Control System, CS-E 50(h)(3)
specifies that the Engine instructions for installation contain the Engine
Control System’s electrical power supply quality requirements. This applies to
any of the configurations listed in paragraph (13)(c) or any new
configurations or novel approach not listed that use Aircraft-Supplied Power.
These quality requirements should include steady state and transient
under-voltage and over-voltage limits for the equipment. The power input
standards of RTCA DO-160/EUROCAE ED-14 are considered to provide an acceptable
definition of such requirements. If RTCA DO-160/EUROCAE ED-14 is used, any
exceptions to the power quality standards cited for the particular category of
equipment specified should be stated.

It is recognised that the
electrical or electronic components of the Engine Control System when operated
on Aircraft-Supplied Power may cease to operate during some low voltage
aircraft power supply conditions beyond those required to sustain normal operation,
but in no case should the operation of the Engine control result in a
Hazardous Engine Effect. In addition, low voltage transients outside the
control system’s declared capability should not cause permanent loss of
function of the control system, or result in inappropriate control system
operation which could cause the Engine to exceed any operational limits, or
cause the transmission of unacceptable erroneous data.

When aircraft power
recovers from a low-voltage condition to a condition within which the control
system is expected to operate normally, the Engine Control System should
resume normal operation. The time interval associated with this recovery
should be contained in the Engine instructions for installation. It is
recognised that Aircraft-Supplied Power conditions may lead to an Engine
shutdown or Engine condition which is not recoverable automatically. In these
cases the Engine should be capable of being restarted, and any special flight
crew procedures for executing an Engine restart during such conditions should
be contained in the Engine instructions for operation. The acceptability of
any non-recoverable Engine operating conditions - as a result of these
Aircraft-Supplied Power conditions - will be determined at aircraft
certification.

If Aircraft-Supplied Power
supplied by a battery is required to meet an "all Engines out"
restart requirement, the analysis according to paragraph 13(c) should result
in a definition of the requirements for this Aircraft-Supplied Power. In any installation
where aircraft electrical power is used to operate the Engine Control System,
such as low Engine speed in-flight re-starting conditions, the effects of any
aircraft electrical bus-switching transients or power transients associated
with application of electrical loads, which could cause an interruption in
voltage or a decay in voltage below that level required for proper control functioning,
should be considered.

(f)        Effects on the
Engine

Where loss of aircraft
power results in a change in Engine Control Mode, the Control Mode transition
should meet the specifications of CS-E 50(b).

For some Engine control
functions that rely exclusively upon Aircraft-Supplied Power, the loss of
electrical power may still be acceptable. Acceptability is based on evaluation
of the change in Engine operating characteristics, experience with similar designs,
or the accommodation designed into the control system.

Examples of such Engine
control functions that have traditionally been reliant on aircraft power
include:

—
Engine start and ignition

—
Thrust Reverser deployment

—
Anti-Icing (Engine probe heat)

—
Fuel Shut-Off

—
Over-speed Protection Systems

—        Non-critical
functions that are primarily performance enhancement functions which, if
inoperative, do not affect the safe operation of the Engine.

(g)       Validation

The applicant should
demonstrate the effects of loss of Aircraft-Supplied Power by Engine test,
system validation test or bench test or combination thereof.

(14)     PISTON
ENGINES

Piston Engines are addressed by the sections
above; no additional specific guidance is necessary.

CS-E 50 specifications are applicable to
these Engines but, when interpretation is necessary, the conditions which
would be acceptable for the aircraft installation should be considered.

(15)     ENGINE,
PROPELLER AND AIRCRAFT SYSTEMS INTEGRATION AND THE INTERRELATION BETWEEN
ENGINE, PROPELLER AND AIRCRAFT CERTIFICATION ACTIVITIES

(a)       Aircraft or
Propeller Functions Integrated into the Engine Control System

This involves the integration of aircraft or
Propeller functions (i.e., those that have traditionally not been considered
Engine control functions), into the Electronic Engine Control System’s
hardware and software.

Examples of this include thrust reverser
control systems, Propeller speed governors, which govern speed by varying
pitch, and ATTCS. When this type of integration activity is pursued, the EECS
becomes part of - and should be included in the aircraft’s SSA, and although
the aircraft functions incorporated into the EECS may receive review at Engine
certification, the acceptability of the safety analysis involving these
functions should be determined at aircraft certification.

The EECS may be configured to contain only
part of the aircraft system’s functionality, or it may contain virtually all
of it. Thrust reverser control systems are an example where only part of the
functionality is included in the EECS. In such cases, the aircraft is
configured to have separate switches and logic (i.e., independent from the
EECS) as part of the thrust reverser control system. This separation of
reverser control system elements and logic provides an architectural means to
limit the criticality of the functions provided by the EECS.

However, in some cases the EECS may be
configured to incorporate virtually all of a critical aircraft function.
Examples of this “virtual completeness” in aircraft functionality are EECS
which contain full authority to govern Propeller speed in turboprop powered
aircraft and ATTCS in turbofan power aircraft.

The first of these examples is considered
critical because, if an Engine fails, the logic in the Engine Control System
should be configured to feather the Propeller on that Engine. Failure to
rapidly feather the Propeller following an Engine Failure results in excessive
drag on the aircraft, and such a condition can be critical to the aircraft.
When functions like these are integrated into the Engine control such that
they render an EECS critical, special attention should be paid to assuring
that no single (including common cause/mode) Failures could cause the critical
Failure condition, e.g. exposure of the EECS to overheat should not cause both
an Engine shutdown and Failure of the Propeller to feather.

The second example, that of an ATTCS, is
considered critical because the system is required to increase the thrust of
the remaining Engine(s) following an Engine Failure during takeoff, and the
increased thrust on the remaining Engines is necessary to achieve the required
aircraft performance.

All of the above examples of integration
involve aircraft functionality that would receive significant review during
aircraft certification.

(b)       Integration of
Engine Control Functions into Aircraft Systems

The trend toward systems integration may
lead to aircraft systems performing functions traditionally considered part of
the Engine Control System. Some designs may use aircraft systems to implement
a significant number of the Engine Control System functions. An example would
be the complex integrated flight and Engine Control Systems – integrated in
aircraft avionics units - which govern Engine speed, rotor speed, rotor pitch
angle and rotor tilt angle in tilt-rotor aircraft.

In these designs, aircraft systems may be
required to be used during Engine certification. In such cases, the Engine
applicant is responsible for specifying the requirements for the EECS in the
instructions for installation and substantiating the adequacy of those
requirements.

An example of limited integration would be
an Engine control which receives a torque output demand signal from the
aircraft and responds by changing the Engine’s fuel flow and other variables
to meet that demand. However, the EECS itself, which is part of the type
design, provides all the functionality required to safely operate the Engine
in accordance with CS-E or other applicable specifications.

(i)        Objective

To satisfy the aircraft specifications, such
as CS 25.901, CS 25.903 and CS 25.1309, an analysis of the consequences of
Failures of the Engine Control System on the aircraft has to be made. The
Engine applicant should, together with the aircraft applicant, ensure that the
software/AEH criticality levels and the safety and reliability objectives for
the Engine electronic control system are consistent with these specifications.

(ii)       Interface
Definition and System Responsibilities

System responsibilities as well as interface
definitions should be identified for the functional as well as hardware and
software aspects between the Engine, Propeller and the aircraft systems in the
appropriate documents.

The Engine/Propeller/aircraft documents
should cover in particular:

—
Functional requirements and
criticality (which may be based on Engine, Propeller and aircraft
considerations);

—
Fault Accommodation strategies;

—
Maintenance strategies;

—
The software/AEH criticality
level (per function if necessary);

—
The reliability objectives
for:

—
LOTC/LOPC events,

—
Transmission of faulty
parameters;

—
The environmental requirements
including the degree of protection against lightning or other electromagnetic
effects (e.g. level of induced voltages that can be supported at the
interfaces);

—
Engine, Propeller and aircraft
interface data and characteristics;

—
Aircraft power supply
requirements and characteristics (if relevant).

(iii)      Distribution of
Compliance Tasks

The tasks for the certification of the
aircraft propulsion system equipped with Electronic Engine Control Systems (EECSs)
may be shared between the Engine, Propeller and aircraft applicants. The
distribution of these tasks between the applicants should be identified and
agreed with the appropriate Engine, Propeller and aircraft authorities. For
further information refer to [AMC 20-1()](#_DxCrossRefBm421436781).

The aircraft certification should deal with
the overall integration of the Engine and Propeller in compliance with the
applicable aircraft specifications.

The Engine certification will address the
functional aspects of the Engine Control System in compliance with the
applicable Engine specifications.

Appropriate evidence provided for Engine
certification should be used for aircraft certification. For example, the
quality of any aircraft function software/AEH and aircraft–Engine interface
logic already demonstrated for Engine certification should need no additional
substantiation for aircraft certification.

Two examples are given below to illustrate
this principle.

(A)      Case of an EECS performing the functions for the control of
the Engine and the functions for the control of the Propeller.

The Engine certification would address all
general requirements such as software/AEH development assurance procedures,
EMI, HIRF and lightning protection levels, effects of loss of
aircraft-supplied power.

The Engine certification would address the
functional aspects for the Engine functions (safety analysis, rate of
LOTC/LOPC events, effect of loss of aircraft-supplied data, etc.). The Fault
Accommodation logic affecting the control of the Engine, for example, will be
reviewed at that time.

The Propeller certification will similarly
address the functional aspects for the Propeller functions. The Fault
Accommodation logic affecting the control of the Propeller, for example, will
be reviewed at that time.

In this example, the Propeller functions and
characteristics defined by the Propeller applicant, which are to be provided
by the Engine Control System, would normally need to be refined by flight
test. The Propeller applicant is responsible for ensuring that these functions
and characteristics, which are provided for use during the Engine
certification programme, define an airworthy Propeller configuration, even if
they have not yet been refined by flight test.

With regard to changes in design, agreement
by all parties involved should be reached so that changes to the Engine
Control System that affect the Propeller system, or vice versa, do not lead to
any inadvertent effects on the other system.

(B)       Case of an aircraft computer performing the functions for the
control of the Engine.

The aircraft certification will address all
general requirements such as software/AEH development assurance procedures,
EMI, HIRF and lightning protection levels.

The aircraft certification will address the
functional aspects for the aircraft functions.

The Engine certification will address the
functional aspects for the Engine functions (safety analysis, rate of LOTC/LOPC
events, effect of loss of aircraft-supplied data, etc.) The Fault
Accommodation logic affecting the control of the Engine, for example, will be
reviewed at that time.

[Amdt 20/2]

[Amdt 20/10]

[Amdt 20/19]

AMC 20-3B Certification of Engines Equipped with Electronic Engine
Control Systems

ED Decision 2020/010/R

(1)       PURPOSE

The existing certification specifications of CS-E for Engine
certification may require specific interpretation for Engines equipped with
Electronic Engine Control Systems (EECS), with special regard to interface
with the certification of the aircraft and/or Propeller when applicable.
Because of the nature of this technology, it has been considered useful to
prepare acceptable means of compliance (AMC) specifically addressing the
certification of these control systems.

Like any AMC, it is issued to outline issues to be considered
during the demonstration of compliance with CS-E.

(2)       SCOPE

This AMC is relevant to Engine certification specifications
for EECS, whether they use electrical or electronic (analogue or digital)
technology. This is in addition to other AMC such as AMC E 50 or
AMC E 80.

It gives guidance on the precautions to be taken for the use
of electrical and electronic technology for Engine control, protection,
limiting and monitoring functions, and, where applicable, for the integration
of aircraft or Propeller functions. In the latter case, this document is
applicable to such functions integrated into the EECS, but only to the extent
that these functions affect compliance with CS-E specifications.

The text deals mainly with the thrust and power functions of
an EECS, since this is the prime function of the Engine. However, there are
many other functions, such as bleed valve control, that may be integrated into
the system for operability reasons. The principles outlined in this AMC apply
to the whole EECS.

This document also discusses the division of compliance tasks
for certification between the applicants for Engine, Propeller (when
applicable), and aircraft type certificates. This guidance relates to issues
to be considered during Engine certification. [AMC 20-1()](#_DxCrossRefBm1926189217) addresses issues
associated with the Engine installation in the aircraft.

The introduction of electrical and electronic technology can
entail the following:

—
greater dependence of the Engine on the
aircraft owing to the increased use of electrical power or data supplied from
the aircraft;

—
increased integration of control and related
indication functions;

—
increased risk of significant Failures that are
common to more than one Engine of the aircraft which might, for example, occur
as a result of:

—
insufficient protection from electromagnetic
disturbance (e.g. lightning, internal or external radiation effects) (see CS-E
50(a)(1), CS E-80 and CS-E 170);

—
insufficient integrity of the aircraft
electrical power supply (see CS-E 50(h));

—
insufficient integrity of data supplied from
the aircraft (see CS-E 50(g));

—
hidden design Faults or discrepancies contained
within the design of the propulsion system control software or airborne electronic
hardware (AEH) (see CS-E 50(f)); or

—
omissions or errors in the system/software/AEH
specification (see CS-E 50(f)).

Appropriatedesign and integration precautions should
therefore be taken to minimise any adverse effects from the above.

(3)       RELEVANT
SPECIFICATIONS AND REFERENCE DOCUMENTS

Although compliance with many CS-E specifications might be
affected by the Engine Control System, the main paragraphs relevant to the
certification of the Engine Control System itself are the following:

<table border="1" cellpadding="0" cellspacing="0" width="570">
<tr>
<td valign="top" width="348">
CS-E
 Specification
</td>
<td valign="top" width="108">
Turbine Engines
</td>
<td valign="top" width="114">
Piston Engines
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 20 (Engine configuration and interfaces)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 25 (Instructions for Continued Airworthiness)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 30 (Assumptions)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 50 (Engine Control System)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 60 (Provision for instruments)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 80 (Equipment)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 110 (Drawing and marking of parts — Assembly of parts)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 130 (Fire prevention)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 140 (Tests-Engine configuration)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 170 (Engine systems and component verification)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 210 (Failure analysis)
</td>
<td valign="top" width="108">
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 250 (Fuel System)
</td>
<td valign="top" width="108">
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 390 (Acceleration tests)
</td>
<td valign="top" width="108">
</td>
<td valign="top" width="114">
ü
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 500 (Functioning)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E-510
 (Safety analysis)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 560 (Fuel system)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 745 (Engine Acceleration)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
</td>
</tr>
<tr>
<td valign="top" width="348">
CS-E
 1030 (Time-limited dispatch)
</td>
<td valign="top" width="108">
ü
</td>
<td valign="top" width="114">
ü
</td>
</tr>
</table>

The following documents are referenced in AMC 20-3B:

—
International Electrotechnical Commission
(IEC), Central Office, 3, rue de Varembé, P.O. Box 131, CH - 1211 GENEVA 20,
Switzerland

—
IEC/PAS 62239, Electronic Component Management
Plans, edition 1.0, dated April 2001

—
IEC/PAS 62240, Use of Semiconductor Devices
Outside Manufacturers’ Specified Temperature Ranges, edition 1.0, dated April
2001

—
RTCA, Inc. 1828 L Street, NW, Suite 805,
Washington, DC 20036 or EUROCAE, 17, rue Hamelin, 75116 Paris, France

—
RTCA DO-254/ EUROCAE ED-80, Design Assurance
Guidance for Airborne Electronic Hardware, dated April 19, 2000

—
RTCA DO-160/EUROCAE ED 14, Environmental
Conditions and Test Procedures for Airborne Equipment

—
[AMC 20-115](#_DxCrossRefBm1926189222)
on software considerations for certification of airborne systems and equipment

—
Aeronautical Systems Center, ASC/ENOI, Bldg
560, 2530 Loop Road West, Wright‑Patterson AFB, OH, USA, 45433-7101

—
MIL-STD-461E, Requirements for the Control of
Electromagnetic Interference Characteristics, dated August 20, 1999

—
MIL-STD-810 E or F, Test Method Standard for
Environmental Engineering, E dated July 14, 1989, F dated January 1, 2000

—
U.S. Department of Transportation, Subsequent
Distribution, Office Ardmore East Business Center, 3341 Q 75th Ave,
Landover, MD, USA, 20785

—
AC 20-136, Protection of Aircraft
Electrical/Electronic Systems Against the Indirect Effects of Lightning, dated
March 5, 1990

—
Society of Automotive Engineers (SAE), 400
Commonwealth Drive, Warrendale, PA 15096-0001 USA or EUROCAE, 17, rue Hamelin,
75116 Paris, France

—
SAE ARP 5412 / EUROCAE ED-84, with Amendment 1
& 2, Aircraft Lightning Environment and Related Test Waveforms, February
2005/May 2001 respectively

—
SAE ARP 5413 / EUROCAE ED-81, with Amendment 1,
Certification of Aircraft Electrical/Electronic Systems for the Indirect
Effects of Lightning, November 1999/August 1999 respectively

—
SAE ARP 5414 / EUROCAE ED-91, with Amendment 1,
Aircraft Lightning Zoning, February 2005/June 1999 respectively

—
SAE ARP 5416 / EUROCAE ED-105, Aircraft
Lightning Test Methods, March 2005/April 2005 respectively

(4)       DEFINITIONS

The words defined in CS-Definitions and in CS-E 15 are
identified by capital letters.

The following figure and associated definitions are provided
to facilitate a clear understanding of the terms used in this AMC.

![Aviation.Bot AI suggestion, not from EASA source: This image is a conceptual diagram illustrating the relationship between different components of an Engine Control System and their corresponding operational modes, providing a visual aid for definitions.

Detailed Description:
The diagram is titled "DEFINITIONS VISUALISED" in bold, underlined, and centered at the top.
It is divided conceptually into two main sections: "SYSTEMS" on the left and "MODES" on the right, both titles are bold and underlined.

Under the "SYSTEMS" section, there is a bold, underlined sub-heading "ENGINE CONTROL SYSTEM". A large rectangular box with a dashed black border encloses two smaller, solid-bordered rectangular boxes, representing the overall Engine Control System.
1.  The top inner box is labeled "Primary system" in bold and italic font. Inside this box, the text reads: "May be one or more lanes (channels)" and "Lanes typically have equal functionality".
2.  The bottom inner box is labeled "Backup system" in bold and italic font. Inside this box, the text reads: "May be hydromechanical control or less capable lane".

Under the "MODES" section, there is a text label "PRIMARY MODE / NORMAL MODE" positioned at the top. Below this, a bold, underlined sub-heading "ALTERNATE MODES" is present. A large rectangular box with a dashed black border encloses four text labels, representing the "ALTERNATE MODES" category.
1.  The first text label inside this dashed box is "ALTERNATE MODE 1".
2.  The second text label is "ALTERNATE MODE 2".
3.  The third text label is "BACKUP MODE 1".
4.  The fourth text label is "BACKUP MODE 2".

Four solid black arrows connect the "SYSTEMS" to the "MODES" section, all pointing from left to right:
1.  An arrow originates from the "Primary system" box and points to the "PRIMARY MODE / NORMAL MODE" text.
2.  Another arrow originates from the "Primary system" box and points to the "ALTERNATE MODE 1" text.
3.  An arrow originates from the "Backup system" box and points to the "BACKUP MODE 1" text.
4.  A final arrow originates from the "Backup system" box and points to the "BACKUP MODE 2" text.

Contextual Linkage:
The diagram visually defines how the "ENGINE CONTROL SYSTEM", comprising a "Primary system" and a "Backup system", relates to various operational "MODES". The "Primary system" is shown to enable both the "PRIMARY MODE / NORMAL MODE" and "ALTERNATE MODE 1". The "Backup system" is shown to enable "BACKUP MODE 1" and "BACKUP MODE 2". The diagram also categorizes "ALTERNATE MODE 1", "ALTERNATE MODE 2", "BACKUP MODE 1", and "BACKUP MODE 2" collectively under the broader heading of "ALTERNATE MODES".](file_tNNDI2wQkpg/image002.png)

(5)       GENERAL

It is recognised that the determination of compliance of the
Engine Control System with the applicable aircraft certification
specifications will only be made during the aircraft certification.

In the case where the installation is unknown at the time of
Engine certification, the applicant for Engine certification should make
reasonable installation and operational assumptions for the target
installation. Any installation limitations or operational issues will be noted
in the instructions for installation or operation, and/or the Type Certificate
Data Sheet (TCDS) (see CS‑E 30 Assumptions).

When possible, early coordination between the Engine and the
aircraft applicants is recommended in association with the relevant
authorities as discussed under Section 15 of this AMC.

(6)       SYSTEM DESIGN AND
VALIDATION

(a)       Control Modes — General

Under CS-E 50(a), the applicant should
perform all necessary testing and analysis to ensure that all Control Modes,
including those which occur as a result of control Fault Accommodation
strategies, are implemented as required.

The need to provide protective functions, such as overspeed
protection, for all Control Modes, including any Alternate Modes, should be
reviewed under the specifications of CS-E 50(c), (d) and (e), and CS-E 210 or
CS-E 510.

Any limitations on operations in Alternate Modes should be
clearly stated in the Engine instructions for installation and operation.

Descriptions of the functioning of the Engine Control System
operating in its Primary and any Alternate Modes should be provided in the
Engine instructions for installation and operation.

Analyses and/or testing are necessary to substantiate that
operating in the Alternate Modes has no unacceptable effect on Engine
durability or endurance. Demonstration of the durability and reliability of
the control system in all modes is primarily addressed by the component
testing of CS-E 170. Performing some portion of the Engine certification
testing in the Alternate Mode(s) and during transition between modes can be
used as part of the system validation required under CS-E 50(a).

(i)        Engine Test Considerations

If the Engine certification tests defined in CS-E are
performed using only the Engine Control System’s Primary Mode in the Full-up
Configuration and if approval for dispatch in the Alternate Mode is requested
by the applicant under CS-E 1030, it should be demonstrated, by analysis
and/or test, that the Engine can meet the defined test-success criteria when
operating in any Alternate Mode that is proposed as a dispatchable configuration
as required by CS-E 1030.

Some capabilities, such as operability, blade-off, rain,
hail, bird ingestion, etc., may be lost in some control modes that are not
dispatchable. These modes do not require engine test demonstration as long as
the installation and operating instructions reflect this loss of capability.

(ii)       Availability

Availability of any Back-up Mode should be established by
routine testing or monitoring to ensure that the Back-up Mode will be
available when needed. The frequency of establishing its availability should
be documented in the Instructions for Continued Airworthiness (ICA).

(b)       Crew Training Modes

This AMC is not specifically intended to apply to any crew
training modes. These modes are usually installation-, and possibly operator-,
specific and need to be negotiated on a case-by-case basis. As an example, one
common application of crew training modes is for simulation of the
‘failed-fixed’ mode on a twin-engine rotorcraft. Training modes should be
described in the Engine instructions for installation and operation as
appropriate. Also, precautions should be taken in the design of the Engine
Control System and its crew interfaces to prevent inadvertent entry into any
training modes. Crew training modes, including lock-out systems, should be
assessed as part of the System Safety Analysis (SSA) of CS-E 50(d).

For control configurations which are not dispatchable, but
for which the applicant seeks to take credit in the system Loss of Thrust (or
Power) Control (LOTC/LOPC) analysis, it may be acceptable to have specific
operating limitations. In addition, compliance with CS‑E 50(a) does not
imply strict compliance with the operability specifications of CS-E 390, CS-E
500 and CS-E 745 in these non-dispatchable configurations, if it can be
demonstrated that, in the intended installation, no likely pilot control
system inputs will result in Engine surge, stall, flame-out or unmanageable
delay in power recovery. For example, in a twin-engine rotorcraft, a
rudimentary Backup System may be adequate since frequent and rapid changes in
power setting with the Backup System may not be necessary.

In addition to these operability considerations, other
factors which should be considered in assessing the acceptability of such
reduced-capability Backup Modes include:

—
the installed operating characteristics of the
Back-up Mode and the differences from the Primary Mode;

—
the likely impact of the Back-up Mode
operations on pilot workload, if the aircraft installation is known;

—        the frequency of transfer from the
Primary Mode to the Back-up Mode (i.e. the reliability of the Primary Mode);frequencies
of transfer of less than 1 per 20 000 engine flight hours have been
considered acceptable.

(d)       Control Transitions

The intent of CS-E 50(b) is to ensure that any control
transitions, which occur as a result of Fault Accommodation, occur in an
acceptable manner.

In general, transition to Alternate Modes should be
accomplished automatically by the Engine Control System. However, systems for
which pilot action is required to engage the Backup Mode may also be
acceptable. For instance, a Fault in the Primary System may result in a
‘failed-fixed’ fuel flow and some action is required by the pilot to engage
the Backup System in order to modulate Engine power. Care should be taken to
ensure that any reliance on manual transition is not expected to pose an
unacceptable operating characteristic, unacceptable crew workload or require
exceptional skill.

The transient change in power or thrust associated with
transfer to Alternate Modes should be reviewed for compliance with CS-E 50(b).
If available, input from the installer should be considered. Although this is
not to be considered a complete list, some of the items that should be
considered when reviewing the acceptability of Control Mode transitions are:

—
The frequency of occurrence of transfers to any
Alternate Mode and the capability of the Alternate Mode. Computed
frequency-of-transfer rates should be supported with data from endurance or
reliability testing, in-service experience on similar equipment, or other
appropriate data.

—
The magnitude of the power, thrust, rotor or
Propeller speed transients.

—
Successful demonstration, by simulation or
other means, of the ability of the Engine Control System to control the Engine
safely during the transition. In some cases, particularly those involving
rotorcraft, it may not be possible to make a determination that the mode
transition provides a safe system based solely on analytical or simulation
data. Therefore, a flight test programme to support this data will normally be
expected.

—
An analysis should be provided to identify
those Faults that cause Control Mode transitions either automatically or
through pilot action.

—
For turboprop or turboshaft engines, the
transition should not result in excessive overspeed or underspeed of the rotor
or Propeller which could cause emergency shutdown, loss of electrical
generator power or the setting-off of warning devices.

The thrust or power change associated with the transition
should be declared in the instructions for installing the Engine.

(i)        Time Delays

Any observable time delays associated with Control Mode,
channel or system transitions or in re-establishing the pilot’s ability to
modulate Engine thrust or power should be identified in the Engine
instructions for installation and operation (see CS-E 50(b)). These delays
should be assessed during aircraft certification.

(ii)       Annunciation to the Flight Crew

If annunciation is necessary to comply with CS-E 50(b)(3),
the type of annunciation to the flight crew should be commensurate with the
nature of the transition. For instance, reversion to an Alternate Mode of
control where the transition is automatic and the only observable changes in
operation of the Engine are different thrust control schedules, would require
a very different form of annunciation to that required if timely action by the
pilot is required in order to maintain control of the aircraft.

The intent and purpose of the cockpit annunciation should be
clearly stated in the Engine instructions for installation and operation, as
appropriate.

(e)       Environmental conditions

Environmental conditions include electromagnetic interference
(EMI), high-intensity radiated fields (HIRF) and lightning. The environmental
conditions are addressed under CS-E 80 and CS-E 170. The following
provides additional guidance for EMI, HIRF and lightning.

(i)        Declared levels

When the installation is known during the Engine type-certification
programme, the Engine Control System should be tested at levels that have been
determined and agreed by the Engine and aircraft applicants. It is assumed
that, by this agreement, the installation can meet the aircraft certification
specifications. Successful completion of the testing to the agreed levels
would be accepted for Engine type certification. This, however, may make the
possibility of installing the Engine dependent on a specific aircraft.

If the aircraft installation is not known or defined at the
time of the Engine certification, in order to determine the levels to be
declared for the Engine certification, the Engine applicant may use the
external threat level defined at the aircraft level and use assumptions on
installation attenuation effects.

If none of the options defined above are available, it is
recommended that the procedures and minimum default levels for HIRF testing should
be agreed with EASA.

(ii)       Test procedures

(A)      General

The installed Engine Control System, including representative

Engine–aircraft interface cables, should be the basis for certification
testing.

EMI test procedures and test levels conducted in accordance
with MIL‑STD‑461 or EUROCAE ED 14/DO-160 have been considered acceptable.

The applicant should use the HIRF test guidelines provided in
EUROCAE ED 14/RTCA DO-160 or equivalent. However, it should be recognised that
the tests defined in EUROCAE ED 14/RTCA DO-160 are applicable at a component
test level, requiring the applicant to adapt these test procedures to a system
level HIRF test to demonstrate compliance with CS-E 80 and CS‑E 170.

For lightning tests, the guidelines of SAE ARP 5412, 5413,
5414 and 5416, and EUROCAE ED 14/RTCA DO-160 would be applicable.

Pin Injection Tests (PIT) are normally conducted as component
tests on the EECS unit and other system components as required. PIT levels are
selected as appropriate from the tables of EUROCAE ED 14/DO-160.

Environmental tests, such as MIL-STD-810, may be accepted in
lieu of EUROCAE ED-14/DO-160 tests where these tests are equal to or more
rigorous than those defined in EUROCAE ED 14/DO-160.

(B)       Open-loop
and Closed-loop Testing

HIRF and lightning tests should be conducted as system tests
on closed-loop or open-loop laboratory set-ups.

The closed-loop set-up is usually provided with hydraulic
pressure to move actuators to close the inner actuating loops. A simplified
Engine simulation may be used to close the outer Engine loop.

Testing should be conducted with the Engine Control System
controlling at the most sensitive operating point, as selected and detailed in
the test plans by the applicant. The system should be exposed to the HIRF and
lightning environmental threats while operating at the selected condition.
There may be a different operating point for HIRF and lightning environmental
threats.

For tests in open- and closed-loop set-ups, the following
factors should also be considered:

—
If a special EECS test software is used, that
software should be developed at the criticality level determined by the Engine
safety assessment process.

—
The Engine Control System should be tested at
the criticality levels that have been determined and agreed by the Engine and
aircraft applicants. It is assumed that by this agreement, the installation
meets the aircraft certification specifications. In some cases, the
application code is modified to include the required test code features.

—
The system test set-up should be capable of
monitoring both the output signals and the input signals.

—
Anomalies observed during open-loop testing on
inputs or outputs should be duplicated on the Engine simulation to determine
whether the resulting power or thrust perturbations comply with the pass–fail
criteria.

(iii)      Pass–Fail Criteria

The pass–fail criteria of CS-E 170 for HIRF and lightning
should be interpreted as ‘no adverse effect’ on the functionality of the
system.

The following are considered adverse effects:

—
a greater than 3 % change of Take-off
Power or Thrust for a period of more than 2 seconds;

—
transfers to Alternate Channels, Backup
Systems, or Alternate Modes;

—
component damage;

—
false annunciation to the flight crew, which
could cause unnecessary or inappropriate flight crew action;

—
erroneous operation of protection systems, such
as overspeed or thrust reverser circuits.

AEH or software design changes implemented after the initial
environmental testing should be evaluated for their effects with respect to
the EMI, HIRF and lightning environment.

(iv)      Maintenance Actions

CS-E 25 requires that the applicant prepare Instructions for
Continued Airworthiness (ICA). These include a maintenance plan. Therefore,
for any protection system that is part of the type design of the Engine
Control System and is required by the system to meet the qualified levels of
EMI, HIRF and lightning, a maintenance plan should be provided to ensure the
continued airworthiness for the parts of the installed system which are
supplied by the Engine type-certificate holder.

The maintenance actions to be considered include periodic
inspections or tests for required structural shielding, wire shields,
connectors, and equipment protection components. Inspections or tests when the
part is exposed may also be considered. The applicant should provide the
engineering validation and substantiation of these maintenance actions.

(v)       Time-Limited Dispatch (TLD)
Environmental Tests

Although TLD is only an optional requirement for
certification (see CS-E 1000 and CS-E 1030), EMI, HIRF and lightning tests for
TLD are usually conducted together with tests conducted for certification.
Acceptable means of compliance are provided in AMC E 1030.

(7)       INTEGRITY OF THE
ENGINE CONTROL SYSTEM

(a)       Objective

The intent of CS-E 50(c) is to establish Engine Control
System integrity requirements consistent with operational requirements of the
various installations. (See also paragraph (4) of AMC E 50).

(b)       Definition of an LOTC/LOPC event

(i)        For turbine Engines intended for CS-25
installations

An LOTC/LOPC event is defined as an event where the
Engine Control System:

—
has lost the capability of modulating thrust or
power between idle and 90% of maximum rated power or thrust, or

—
suffers a Fault which results in a thrust or
power oscillation greater than the levels given in paragraph (7)(c) of this
AMC, or

—
has lost the capability to govern the Engine in
a manner which allows compliance with the operability specifications given in
CS-E 500(a) and CS-E 745.

(ii)       For turbine Engines intended for
rotorcraft

An LOPC event is defined as an event where the Engine Control
System:

—
has lost the capability of modulating power
between idle and 90% of maximum rated power at the flight condition, except
OEI power ratings, or

—
suffers a Fault which results in a power
oscillation greater than the levels given in paragraph (7)(c) of this AMC, or

—
has lost the capability to govern the Engine in
a manner which allows compliance with the operability specifications given in
CS-E 500(a) and CS-E 745, with the exception that the inability to meet the
operability specifications in the Alternate Modes may not be included as LOPC
events.

—
Single Engine rotorcraft will be required to
meet the operability specifications in the Alternate Mode(s), unless the lack
of this capability is demonstrated to be acceptable at the aircraft level.
Engine operability in the Alternate Mode(s) is considered a necessity if:

—
the control transitions to the Alternate Mode
more frequently than the acceptable LOPC rate, or

—
normal flight crew activity requires rapid
changes in power to safely fly the aircraft.

—
For multi-Engine rotorcraft, the LOPC
definition may not need to include the inability to meet the operability
specifications in the Alternate Mode(s). This may be considered acceptable
because when one Engine control transitions to an Alternate Mode, which may
not have robust operability, that Engine can be left at reasonably fixed power
conditions. The Engine(s) with the normally operating control(s) can change
power – as necessary – to complete aircraft manoeuvres and safely land the
aircraft. Demonstration of the acceptability of this type of operation may be
required at aircraft certification.

(iii)      For turbine Engines intended for other
installations

A LOTC/LOPC event is
defined as an event where the Engine Control System:

—
has lost the capability of modulating thrust or
power between idle and 90% of maximum rated power or thrust, or

—
suffers a Fault which results in a thrust or
power oscillation that would impact controllability in the intended
installation, or

—
has lost the capability to govern the Engine in
a manner which allows compliance with the operability specifications given in
CS-E 500(a) and CS-E 745, as appropriate.

(iv)      For
piston Engines

An LOPC event is
defined as an event where the Engine Control System:

—
has lost the capability of modulating power
between idle and 85% of maximum rated power at all operating conditions, or

—
suffers a Fault which results in a power
oscillation greater than the levels given in paragraph (7)(c) of this AMC, or

—        has lost the capability to govern the Engine in a manner
which allows compliance with the operability specifications given in CS-E 390.

(v)       For
engines incorporating functions for Propeller control integrated in the EECS

The following Faults or Failures should be considered as
additional LOPC events:

—
inability to command a change in pitch,

—
uncommanded change in pitch,

—        uncontrollable Propeller
torque or speed fluctuation.

Any uncommanded thrust or power oscillations should be of
such a magnitude as not to impact aircraft controllability in the intended
installation. Thrust or power oscillations less than 10% peak to peak of
Take-off Power and/or Thrust have been considered acceptable in some
installations, where the failure affects one engine only. Regardless of the
levels discussed herein, if the flight crew has to shut down an Engine because
of unacceptable thrust or power oscillations caused by the control system, such
an event would be deemed an in-service LOTC/LOPC event.

(d)       Acceptable LOTC/LOPC rate

The applicant may propose an LOTC/LOPC
rate other than those below. Such a proposal should be substantiated in
relation to the criticality of the Engine and control system relative to the
intended installation. The intent is to show equivalence of the LOTC/LOPC rate
to existing systems in comparable installations.

(i)        For
turbine Engines

The EECS should not cause more than one LOTC/LOPC event per
100 000 engine flight hours.

(ii)       For piston Engines

An LOPC rate of 45 per million engine flight hours (or 1 per
22,222 engine flight hours) has been shown to represent an acceptable level
for the most complex EECS. As a result of the architectures used in many of
the EECS for these engines, the functions are implemented in independent
system elements. These system elements or sub-systems can be fuel control, or
ignition control, or others. If a system were to contain only one element such
as fuel control, then the appropriate total system level would be 15 LOPC
events per million engine flight hours. So the system elements are then
additive up to a max of 45 LOPC events per million hours. For example, an EEC
system comprised of fuel, ignition, and wastegate control functions should
meet a total system reliability of 15+15+15 = 45 LOPC events per million
engine flight hours. This criterion is then applied to the entire system and
not allocated to each of the subsystems. Note that a maximum of 45 LOPC events
per million engine flight hours are allowed, regardless of the number of
subsystems. For example, if the EEC system includes more than three
subsystems, the sum of the LOPC rates for the total system should not exceed
45 LOPC events per million engine flight hours for all of the electrical and
electronic elements.

(e)       LOTC/LOPC Analysis

A system reliability analysis should be submitted to
substantiate the agreed LOTC/LOPC rate for the Engine Control System. A
numerical analysis such as a Markov model analysis, fault tree analysis or
equivalent analytical approach is expected.

The analysis should address all components in the system that
can contribute to LOTC/LOPC events. This includes all electrical, mechanical,
hydromechanical, and pneumatic elements of the Engine Control System. This
LOTC/LOPC analysis should be done in conjunction with the System Safety Assessment
required under CS-E 50(d). Paragraph (8) of this AMC provides additional
guidance material.

The engine fuel pump is generally not included in the
definition of the Engine Control System. It is usually considered part of the
fuel delivery system.

The LOTC/LOPC analysis should include those sensors or
elements which may not be part of the Engine type design, but which may
contribute to LOTC/LOPC events. An example of this is the throttle or power
lever transducer, which is usually supplied by the installer. The effects of
loss, corruption or Failure of Aircraft-Supplied Data should be included in
the Engine Control System’s LOTC/LOPC analysis. The reliability and interface
requirements for these non-Engine type design elements should be contained in the
Engine instructions for installation. It needs to be ensured that there is no
double counting of the rate of Failure of non-engine parts within the aircraft
system safety analyses.

The LOTC/LOPC analysis should consider all Faults, both
detected and undetected. Any periodic maintenance actions needed to find and
repair both Covered and Uncovered Faults, in order to meet the LOTC/LOPC rate,
should be contained in the Engine instructions for continued airworthiness.

(f)        Commercial or Industrial Grade
Electronic Parts

When the Engine type design specifies commercial or
industrial grade electronic components, which are parts not manufactured to
military standards, the applicant should have the following data available for
review, as applicable:

—
Reliability data that substantiates the Failure
rate for each component used in the LOTC/LOPC analysis and the SSA for each
commercial and industrial grade electrical component specified in the design.

—
The applicant’s procurement, quality assurance,
and process control plans for the vendor-supplied commercial and industrial
grade parts. These plans should ensure that the parts will be able to maintain
the reliability level specified in the approved Engine type design.

—
Unique databases for similar components
obtained from different vendors, because commercial and industrial grade parts
may not all be manufactured to the same accepted industry standard, such as
military component standards.

—
Commercial and industrial grade parts have
typical operating ranges of 0 degrees to +70 degrees Celsius and -40 degrees
to +85 degrees Celsius, respectively. Military grade parts are typically rated
at -54 degrees to 125 degrees Celsius. Commercial and industrial grade parts
are typically defined in these temperature ranges in vendor parts catalogues.
If the declared temperature environment for the Engine Control System exceeds
the stated capability of the commercial or industrial grade electronic components,
the applicant should substantiate that the proposed extended range of the
specified components is suitable for the installation and that the Failure
rates used for those components in the SSA and LOTC/LOPC analyses is
appropriately adjusted for the extended temperature environment. Additionally,
if commercial or industrial parts are used in an environment beyond their
specified rating and cooling provisions are required in the design of the
EECS, the applicant should specify these provisions in the instructions for
installation to ensure that the provisions for cooling are not compromised. Failure
modes of the cooling provisions included in the EECS design that cause these
limits to be exceeded should be considered in determining the probability of
Failure.

—
Two examples of industry published documents
which provide guidance on the application of commercial or industrial grade
components are:

—
IEC/PAS 62239, Electronic Component Management
Plans

—
IEC/PAS 62240, Use of Semiconductor Devices
Outside Manufacturers’ Specified Temperature Ranges

When any electrical or electronic components are changed, the
SSA and LOTC/LOPC analyses should be reviewed with regard to the impact of any
changes in component reliability. Component, subassembly or assembly level
testing may be required by the Agency to substantiate a change that introduces
a commercial or industrial part(s). However, such a change would not be
classified as ‘significant’ with respect to Part 21.A.101(b)1.

(g)       Single Fault Accommodation

Compliance with the single Fault specifications of CS-E 50(c)(2)
and (3) may be substantiated by a combination of tests and analyses. The
intent is that single Failures or malfunctions in the Engine Control System’s
components, in its fully operational condition, do not result in a Hazardous
Engine Effect. In addition, in its full-up configuration the control system
should be essentially single Fault tolerant of electrical/electronic component
Failures with respect to LOTC/LOPC events. For dispatchable configurations
refer to CS-E 1030 and AMC E 1030.

It is recognised that to achieve true single Fault tolerance
for LOTC/LOPC events could require a triplicated design approach or a design
approach with 100% Fault detection. Currently, systems have been designed with
dual, redundant channels or with Back-up Systems that provide what has been
called an "essentially single Fault tolerant" system. Although these
systems may have some Faults that are not Covered Faults, they have
demonstrated excellent in-service safety and reliability, and have proven to
be acceptable.

The objective, of course, is to have all the Faults addressed
as Covered Faults. Indeed, the dual channel or Back-up system configurations
do cover the vast majority of potential electrical and electronic Faults.
However, on a case-by-case basis, it may be appropriate for the applicant to
omit some coverage because detection or accommodation of some
electrical/electronic Faults may not be practical. In these cases, it is
recognised that single, simple electrical or electronic components or circuits
can be employed in a reliable manner, and that requiring redundancy in some
situations may not be appropriate. In these circumstances, Failures in some
single electrical or electronic components, elements or circuits may result in
an LOTC/LOPC event. This is what is meant by the use of the term
“essentially”, and such a system may be acceptable.

(h)       Local Events

Examples of local events to be considered under CS-E 50(c)(4)
include:

—
Overheat conditions, for example, those resulting
from hot air duct bursts,

—
Fires, and

—
Fluid leaks or mechanical disruptions which
could lead to damage to control system electrical harnesses, connectors, or
the control unit(s).

These local events would normally be limited to one Engine.
Therefore, a local event is not usually considered to be a common mode event,
and common mode threats, such as HIRF, lightning and rain, are not considered
local events.

When demonstration that there is no Hazardous Engine Effect
is based on the assumption that another function exists to afford the
necessary protection, it should be shown that this function is not rendered
inoperative by the same local event on the Engine (including destruction of
wires, ducts, power supplies).

It is considered that an overheat condition exists when the
temperature of the system components is greater than the maximum safe design
operating temperature for the components, as declared by the Engine applicant
in the Engine instructions for installation. The Engine Control System should
not cause a Hazardous Engine Effect when the components or units of the system
are exposed to an overheat or over-temperature condition. Specific design
features or analysis methods may be used to show compliance with respect to
the prevention of Hazardous Engine Effects. Where this is not possible, for
example, due to the variability or the complexity of the Failure sequence,
then testing may be required.

The Engine Control System, including the electrical,
electronic and mechanical parts of the system, should comply with the fire
specifications of CS-E 130 and the interpretative material of AMC E 130 is
relevant. This rule applies to the elements of the Engine Control System which
are installed in designated fire zones.

There is no probability associated with CS-E 50(c)(4). Hence,
all foreseeable local events should be considered. It is recognised, however,
that it is difficult to address all possible local events in the intended
aircraft installation at the time of Engine certification. Therefore, sound
Engineering judgement should be applied in order to identify the reasonably
foreseeable local events. Compliance with this specification may be shown by
considering the end result of the local event on the Engine Control System.
The local events analysed should be well documented to aid in certification of
the Engine installation.

The following guidance applies to Engine Control System
wiring:

—
Each wire or combination of wires interfacing
with the EECS that could be affected by a local event should be tested or
analysed with respect to local events. The assessment should include opens,
shorts to ground and shorts to power (when appropriate) and the results should
show that Faults result in identified responses and do not result in Hazardous
Engine Effects.

—
Engine control unit aircraft interface wiring
should be tested or analysed for shorts to aircraft power, and these “hot”
shorts should result in an identified and non-Hazardous Engine Effect. Where
aircraft interface wiring is involved, the installer should be informed of the
potential effects of interface wiring Faults by means of information provided
in the Engine instructions for installation. It is the installer’s
responsibility to ensure that there are no wiring Faults which could affect
more than one Engine. Where practical, wiring Faults should not affect more
than one channel. Any assumptions made by the Engine applicant regarding
channel separation should be included in the LOTC/LOPC analysis.

—
Where physical separation of conductors is not
practical, co-ordination between the Engine applicant and the installer should
ensure that the potential for common mode Faults between Engine Control
Systems is eliminated, and between channels on one Engine is minimised.

The applicant should assess by analysis or test the effects
of fluid leaks impinging on components of the Electronic Engine Control
System. Such conditions should not result in a Hazardous Engine Effect, nor
should the fluids be allowed to impinge on circuitry or printed circuit boards
and result in a potential latent Failure condition.

(8)       SYSTEM SAFETY
ASSESSMENT

(a)       Scope of the assessment

The system safety assessment (SSA) required under CS-E 50(d)
should address all operating modes, and the data used in the SSA should be
substantiated.

The LOTC/LOPC analysis described in Section 7 is a subset of
the SSA. The LOTC/LOPC analysis and SSA may be separate or combined as a
single analysis.

The SSA should consider all Faults, both detected and
undetected, and their effects on the Engine Control System and the Engine
itself. The intent is primarily to address the Faults or malfunctions which
only affect one Engine Control System, and therefore only one Engine. However,
Faults or malfunctions in aircraft signals, including those in a multi-engine
installation that could affect more than one Engine, should also be included
in the SSA; these types of Faults are addressed under CS-E 50(g).

The Engine Control System SSA and LOTC/LOPC analysis, or
combined analyses, should identify the applicable assumptions and installation
requirements and establish any limitations relating to Engine Control System
operation. These assumptions, requirements, and limitations should be stated
in the Engine instructions for installation and operation as appropriate. If
necessary, the limitations should be contained in the airworthiness
limitations section of the instructions for continued airworthiness in accordance
with CS-E 25(b)(1).

The SSA should address all Failure effects identified under
CS-E 510 or CS-E 210, as appropriate. A summary should be provided, listing
the malfunctions or Failures and their effects caused by the Engine Control
System, such as:

—
Failures affecting power or thrust resulting in
LOTC/LOPC events.

—
Failures which result in the Engine’s inability
to meet the operability specifications. If these Failure cases are not
considered as LOPC events according to paragraph (7)(b)(ii) of this AMC, the
expected frequency of occurrence for these events should be documented.

—
Transmission of erroneous parameters which
could lead to thrust or power changes greater than 3% of Take-off Power or
Thrust (10% for piston engines installations) (e.g., false high indication of
the thrust or power setting parameter) or to Engine shutdown (e.g., high EGT
or turbine temperatures or low oil pressure).

—
Failures affecting functions included in the
Engine Control System, which may be considered aircraft functions (e.g.
Propeller control, thrust reverser control, control of cooling air, control of
fuel recirculation)

—
Failures resulting in Major Engine Effects and
Hazardous Engine Effects.

The SSA should also consider all signals used by the Engine
Control System, in particular any cross-Engine control signals and air signals
as described in CS-E 50(i).

The criticality of functions included in the Engine Control
System for aircraft level functions needs to be defined by the aircraft
applicant.

(b)       Criteria

The SSA should demonstrate or provide the following:

(i)        Compliance with CS-E 510 or CS-E 210,
as appropriate.

(ii)       For Failures leading to LOTC/LOPC events,compliance
with the agreed LOTC/LOPC rate for the intended installation (see paragraph
(7)(d) of this AMC).

(iii)      For Failures affecting Engine operability
but not leading to LOPC events,compliance
with the expected total frequency of occurrence of Failures that result in
Engine response that is non-compliant with CS-E 390, CS-E 500(a) and CS-E 745
specifications (as appropriate). The acceptability of the frequency of
occurrence for these events - along with any aircraft flight deck indications
deemed necessary to inform the flight crew of such a condition - will be
determined at aircraft certification.

(iv)      The consequence of the transmission of a
faulty parameter

The consequence of the transmission of a faulty parameter by
the Engine Control System should be identified and included, as appropriate,
in the LOTC/LOPC analysis. Any information necessary to mitigate the
consequence of a faulty parameter transmission should be contained in the
Engine operating instructions.

For example, the Engine operating instructions may indicate
that a display of zero oil pressure be ignored in-flight if the oil quantity
and temperature displays appear normal. In this situation, Failure to transmit
oil pressure or transmitting a zero oil pressure signal should not lead to an
Engine shutdown or LOTC/LOPC event. Admittedly, flight crew initiated
shutdowns have occurred in-service during such conditions. In this regard, if
the Engine operating instructions provide information to mitigate the condition,
then control system Faults or malfunctions leading to the condition do not
have to be included in the LOTC/LOPC analysis. In such a situation, the loss
of multiple functions should be included in the LOTC/LOPC analysis. If the
display of zero oil pressure and zero oil quantity (or high oil temperature)
would result in a crew initiated shutdown, then those conditions should be
included in the systems LOTC/LOPC analysis.

In multi-engine aeroplanes, Faults that result in thrust or
power changes of less than approximately 10% of Take-off Power or Thrust may
be undetectable by the flight crew. This level is based on pilot assessment
and has been in use for a number of years. The pilots indicated that flight
crews will note the Engine operating differences when the difference is
greater than 10% in asymmetric thrust or power.

The detectable difference level for Engines for other
installations should be agreed with the installer.

When operating in the take-off envelope, Uncovered Faults in
the Engine Control System which result in a thrust or power change of less
than 3% (10% for piston engines installations), are generally considered
acceptable. However, this does not detract from the applicant’s obligation to
ensure that the full-up system is capable of providing the declared minimum
rated thrust or power. In this regard, Faults which could result in small
thrust changes should be random in nature and detectable and correctable during
routine inspections, overhauls or power-checks.

The frequency of occurrence of Uncovered Faults that result
in a thrust or power change greater than 3% of Take-off Power or Thrust, but
less than the change defined as an LOTC/LOPC event, should be contained in the
SSA documentation. There are no firm specifications relating to this class of
Faults for Engine certification; however the rate of occurrence of these types
of Faults should be reasonably low, in the order of 10-4 events per
Engine flight hour or less. These Faults may be required to be included in
aircraft certification analysis.

Signals sent from one Engine Control System to another in an
aeroplane installation, such as signals used for an Automatic Take-off Thrust
Control System (ATTCS), synchrophasing, etc., are addressed under CS-E 50(g).
They should be limited in authority by the receiving Engine Control System, so
that undetected Faults do not result in an unacceptable change in thrust or
power on the Engine using those signals. The maximum thrust or power loss on
the Engine using a cross-Engine signal should generally be limited to 3%
absolute difference of the current operating condition.

Note: It is recognised that ATTCS, when activated, may
command a thrust or power increase of 10% or more on the remaining Engine(s).
It is also recognised that signals sent from one Engine control to another in
a rotorcraft installation, such as load sharing and One Engine Inoperative
(OEI), can have a much greater impact on Engine power when those signals fail.
Data of these Failure modes should be contained in the SSA.

When operating in the take-off envelope, detected Faults in
the Engine Control System, which result in a thrust or power change of up to
10% (15% for piston engines) may be acceptable if the total frequency of
occurrence for these types of Failures is relatively low. The predicted
frequency of occurrence for this category of Faults should be contained in SSA
documentation. It should be noted that requirements for the allowable
frequency of occurrence for this category of Faults and any need for a flight
deck indication of these conditions would be reviewed during aircraft
certification. A total frequency of occurrence in excess of 10–4
events per Engine flight hour would not normally be acceptable.

Detected Faults in signals exchanged between Engine Control
Systems should be accommodated so as not to result in greater than a 3% thrust
or power change on the Engine using the cross-Engine signals.

(9)       PROTECTIVE FUNCTIONS

(a)       Rotor Over-speed Protection.

Rotor over-speed protection is usually achieved by providing
an independent over-speed protection system, such that it requires two
independent Faults or malfunctions (as described below) to result in an
uncontrolled over-speed.

The following guidance applies if the rotor over-speed
protection is provided solely by an Engine Control System protective function.

For dispatchable configurations, refer to CS-E 1030 and AMC E
1030.

The SSA should show that the probability per Engine flight
hour of an uncontrolled over-speed condition from any cause in combination
with a Failure of the over-speed protection system to function is less than
one event per hundred million hours (a Failure rate of 10–8 events per Engine
flight hour).

The over-speed protection system would be expected to have a
Failure rate of less than 10–4 Failures per engine flight hour to ensure the
integrity of the protected function.

A self-test of the over-speed protection system to ensure its
functionality prior to each flight is normally necessary for achieving the
objectives. Verifying the functionality of the over-speed protection system at
Engine shutdown and/or start-up is considered adequate for compliance with
this requirement. It is recognised that some Engines may routinely not be shut
down between flight cycles. In this case this should be accounted for in the
analyses.

Because in some over-speed protection systems there are
multiple protection paths, there will always be uncertainty that all paths are
functional at any given time. Where multiple paths can invoke the over-speed
protection system, a test of a different path may be performed each Engine
cycle. The objective is that a complete test of the over-speed system,
including electro-mechanical parts, is achieved in the minimum number of
Engine cycles. This is acceptable so long as the system meets a 10-4
Failure rate.

The applicant may provide data that demonstrates that the
mechanical parts (this does not include the electro-mechanical parts) of the
over-speed protection system can operate without Failure between stated
periods, and a periodic inspection may be established for those parts. This
data is acceptable in lieu of testing the mechanical parts of the sub-system
each Engine cycle.

(b)       Other protective functions

The Engine Control System may perform other protective
functions. Some of these may be Engine functions, but others may be aircraft
or Propeller functions. Engine functions should be considered under the
guidelines of this AMC. The integrity of other protective functions provided
by the Engine Control System should be consistent with a safety analysis
associated with those functions, but if those functions are not Engine
functions, they may not be a part of Engine certification.

As Engine Control Systems become increasingly integrated into
the aircraft and Propeller systems, they are incorporating protective
functions that were previously provided by the aircraft or Propeller systems.
Examples are reducing the Engine to idle thrust if a thrust reverser deploys
and providing the auto-feather function for the Propeller when an Engine
fails.

The reliability and availability associated with these
functions should be consistent with the top level hazard assessment of
conditions involving these functions. This will be completed during aircraft
certification.

For example, if an Engine Failure with loss of the
auto-feather function is catastrophic at the aircraft level - and the
auto-feather function is incorporated into the Engine Control System - the
applicant will have to show for CS-25 installations (or CS-23 installations
certified to CS-25 specifications) that an Engine Failure with loss of the
auto-feather function cannot result from a single control system Failure, and
that combinations of control system Failures, or Engine and control system
Failures, which lead to a significant Engine loss of thrust or power with an
associated loss of the autofeather function may be required to have an
extremely improbable event rate (i.e., 10-9 events per Engine flight hour).

Although these functions await evaluation at the aircraft
level, it is strongly recommended that, if practicable, the aircraft level
hazard assessment involving these functions be available at the time of the
Engine Control System certification. This will facilitate discussions and
co-ordination between the Engine and aircraft certification teams under the
conditions outlined in paragraph (15) of this AMC. It is recognised that this
co-ordination may not occur for various reasons. Because of this, the applicant
should recognise that although the Engine may be certified, it may not be
installable at the aircraft level.

The overall requirement is that the safety assessment of the
Engine Control System should include all Failure modes of all functions
incorporated in the system. This includes those functions which are added to
support aircraft certification, so that the information of those Failure modes
will get properly addressed and passed on to the installer for inclusion in
the airframe SSA. Information concerning the frequencies of occurrence of
those Failure modes may be needed as well.

(10)     SOFTWARE AND AIRBORNE
ELECTRONIC HARDWARE (AEH)DESIGN AND IMPLEMENTATION

(a)       Objective

For Engine Control Systems that use software/AEH, the
objective of CS-E 50(f) is to prevent as far as possible software/AEH errors
that would result in an unacceptable effect on power or thrust, or any unsafe
condition.

In multiple Engine installations, the possibility of software/AEH
errors that are common to more than one Engine Control System may determine
the criticality level of the software/AEH.

(b)       Approved Methods

Methods for developing software/AEH that are compliant with
the guidelines contained in the latest edition of [AMC 20-115](#_DxCrossRefBm1926189222)/[AMC 20-152](#_DxCrossRefBm1926189221) are acceptable methods.
Alternative methods for developing software/AEH may be proposed by the
applicant and are subject to approval by EASA.

Software/AEH which was not developed using the versions of
ED-12/ED-80 referenced in the latest edition of [AMC 20-115](#_DxCrossRefBm1926189222)/[AMC 20-152](#_DxCrossRefBm1926189221) is referred to as legacy
software/AEH. In general, changes made to legacy software/AEH applicable to
its original installation are assured in the same manner as the original
certification. When legacy software/AEH is used in a new aircraft installation
that requires the latest edition of [AMC 20‑115](#_DxCrossRefBm1926189222)/[AMC 20‑152](#_DxCrossRefBm1926189221), the original approval of
the legacy software/AEH is still valid, assuming equivalence to the required
software/AEHcriticalitylevel can be ascertained. If the software/AEH
development method equivalence is acceptable to EASA, taking into account the
conditions defined in the latest edition of [AMC 20-115](#_DxCrossRefBm1926189222)/[AMC 20-152](#_DxCrossRefBm1926189221), the legacy software/AEH
can be used in the new installation. If equivalence cannot be substantiated,
all the software changes should be assured through the use of the latest
edition of [AMC 20-115](#_DxCrossRefBm1926189222) for software
or of [AMC 20-152](#_DxCrossRefBm1926189221) for AEH.

Note: In this AMC, the ‘criticality level’ is used to reflect
either the software level of a software item or the AEH design assurance level
(or DAL) of an AEH item.

The software/AEH criticality level is determined by the
Engine safety assessment process. ED-79A/ARP4754A and ARP4761 provide
guidelines on how to conduct an aircraft/Engine/system safety assessment
process. The Engine software/AEH should be developed at the criticality levels
that have been determined and agreed by the Engine and aircraft applicants. It
is assumed that by this agreement, the aircraft certification specifications
are met.

Determination of the appropriate software/AEH criticality
level may depend on the Failure modes and consequences of those Failures. For
example, it is possible that Failures resulting in significant thrust or power
increases or oscillations may be more severe than an Engine shutdown and,
therefore, the possibility of these types of Failures should be considered
when selecting a given software/AEH criticality level.

(d)       On-Board or Field Software Loading and
Part Number Marking

The following guidelines should be followed when on-board or
field loading of Electronic Engine Control software and associated Electronic
Part Marking (EPM) is implemented.

For software changes, the software to be loaded should have
been documented by an approved design change and released with a service
bulletin.

For an EECS unit having separate part numbers for hardware
and software, the software part number(s) need not be displayed on the unit as
long as the software part number(s) is(are) embedded in the loaded software
and can be verified by electronic means. When new software is loaded into the
unit, the same verification requirement applies and the proper software part
number should be verified before the unit is returned to service.

For an EECS unit having only one part number, which
represents a combination of a software and hardware build, the unit part
number on the nameplate should be changed or updated when the new software is
loaded. The software build or version number should be verified before the
unit is returned to service.

The configuration control system for an EECS that will be
onboard/field loaded and using electronic part marking should be approved. The
drawing system should provide a compatibility table that tabulates the
combinations of hardware part numbers and software versions that have been
approved by the Agency. The top-level compatibility table should be under
configuration control, and it should be updated for each change that affects
hardware/software combinations. The applicable service bulletin should define the
hardware configurations with which the new software version is compatible.

The loading system should be in compliance with the
guidelines of the latest edition of [AMC 20-115](#_DxCrossRefBm1926189222).

If the applicant proposes more than one source for loading,
(e.g., diskette, mass storage, Secure Disk card, USB stick flash, etc.), all
sources should comply with these guidelines.

The service bulletin should require verification that the
correct software version has been loaded after installation on the aircraft.

(e)       Software Change Category

The processes and methods used to change software should not
affect the software level of that software. For classification of software
changes, refer to §4 in Appendix A of GM 21.A.91.

(f)        Software Changes by Others than the TC
Holder

There are two types of potential software changes that could
be implemented by someone other than the original TC holder:

—
option-selectable software, or

—
user-modifiable software (UMS).

Option-selectable changes would have to be pre-certified
utilising a method of selection which has been shown not to be capable of
causing a control malfunction.

UMS is software intended for modification by the aircraft
operator without review by the certification authority, the aircraft
applicant, or the equipment vendor. For Engine Control Systems, UMS has
generally not been applicable. However, approval of UMS, if required, would be
addressed on a case-by-case basis.

In principle, persons other than the TC holder may modify the
software within the modification constraints defined by the TC holder, if the
system has been certified with the provision for software user modifications.
To certify an Electronic Engine Control System with the provision for software
modification by others than the TC holder, the TC holder should (1) provide
the necessary information for approval of the design and implementation of a
software change, and (2) demonstrate that the necessary precautions have been
taken to prevent the user modification from affecting Engine airworthiness, especially
if the user modification is incorrectly implemented.

In the case where the software is changed in a manner not
pre-allowed by the TC holder as “user modifiable”, the “non-TC holder”
applicant will have to comply with the requirements given in Part 21, subpart
E.

(11)     RESERVED

(12)     AIRCRAFT-SUPPLIED
DATA

(a)       Objective

As required by CS-E 50(g), in case of loss, interruption, or
corruption of Aircraft-Supplied Data, the Engine should continue to function
in a safe and acceptable manner, without unacceptable effects on thrust or
power, Hazardous Engine Effects, or loss of ability to comply with the
operating specifications of CS-E 390, CS-E 500(a) and CS-E 745, as
appropriate.

(b)       Background

Historically, regulatory practice was to preserve the Engine
independence from the aircraft. Hence even with very reliable architecture,
such as triply redundant air data computer (ADC) systems, it was required that
the Engine Control System provided an independent control means that could be
used to safely fly the aircraft should all the ADC signals be lost.

However, with the increased Engine-aircraft integration that
is currently occurring in the aviation industry and with the improvement in
reliability and implementation of Aircraft-Supplied Data, the regulatory
intent is being revised to require that Fault Accommodation be provided
against single Failures of Aircraft-Supplied Data. This may include Fault
Accommodation by transition into another Control Mode that is independent of
Aircraft-Supplied Data.

The Engine Control System’s LOTC/LOPC analysis should contain
the effects of air data system Failures in all allowable Engine Control System
and air data system dispatch configurations.

When Aircraft-Supplied Data can affect Engine Control System
operation, the applicant should address the following items, as applicable, in
the SSA or other appropriate documents:

—
Software in the data path to the EECS should be
at a level consistent with that defined for the EECS. The data path may
include other aircraft equipment, such as aircraft thrust management computers,
or other avionics equipment.

—
The applicant should state in the instructions
for installation that the aircraft applicant is responsible for ensuring that
changes to aircraft equipment, including software, in the data path to the
Engine do not affect the integrity of the data provided to the Engine as
defined by the Engine instructions for installation.

—
The applicant should supply the effects of
faulty and corrupted Aircraft-Supplied Data on the EECS in the Engine
instructions for installation.

—
The instructions for installation should state
that the installer should ensure that those sensors and equipment involved in
delivering information to the EECS are capable of operating in the EMI, HIRF
and lightning environments, as defined in the certification basis for the
aircraft, without affecting their proper and continued operation.

—
The applicant should state the reliability
level for the Aircraft-Supplied Data that was used as part of the SSA and
LOTC/LOPC analysis as an “assumed value” in the instructions for installation.

As stated in CS-E 50(g), thrust and power command signals
sent from the aircraft are not subject to the specifications of CS-E 50(g)(2).
If the aircraft thrust or power command system is configured to move the Engine
thrust or power levers or transmit an electronic signal to command a thrust or
power change, the Engine Control System merely responds to the command and
changes Engine thrust or power as appropriate. The Engine Control System may
have no way of knowing that the sensed throttle or power lever movement was
correct or erroneous.

In both the moving throttle (or power lever) and non-moving
throttle (or power lever) configurations, it is the installer’s responsibility
to show that a proper functional hazard analysis is performed on the aircraft
system involved in generating Engine thrust or power commands, and that the
system meets the appropriate aircraft’s functional hazard assessment safety
related specifications. This task is an aircraft certification issue, however
Failures of the system should be included in the Engine’s LOTC/LOPC analysis.

The applicant should prepare a Fault Accommodation chart that
defines the Fault Accommodation architecture for the Aircraft-Supplied Data.

There may be elements of the Engine Control System that are
mounted in the aircraft and are not part of the Engine type design, but which
are dedicated to the Engine Control System and powered by it, such as a
throttle position resolver. In these instances, such elements are considered
to be an integral component of the Electronic Engine Control System and are
not considered aircraft data.

In the case where the particular Failure modes of the
aircraft air data may be unknown, the typical Failure modes of loss of data
and erroneous data should be assumed. The term “erroneous data” is used herein
to describe a condition where the data appears to be valid but is incorrect.

Such assumptions and the results of the evaluation of
erroneous aircraft data should be provided to the installer.

The following are examples of possible means of
accommodation:

—
Provision of an Alternate Mode that is
independent of Aircraft-Supplied Data.

—
Dual sources of aircraft-supplied sensor data
with local Engine sensors provided as voters and alternate data sources.

—
Use of synthesised Engine parameters to control
or as voters. When synthesised parameters are used for control or voting
purposes, the analysis should consider the impact of temperature and other
environmental effects on those sensors whose data are used in the synthesis.
The variability of any data or information necessary to relate the data from
the sensors used in the synthesis to the parameters being synthesised should
also be assessed.

—
Triple redundant ADC systems that provide the
required data.

If for aircraft certification it is intended to show that the
complete loss of the aircraft air data system itself is extremely improbable,
then it should be shown that the aircraft air data system is unaffected by a
complete loss of aircraft generated power, for example, backed up by battery
power. (See [AMC 20-1](#_DxCrossRefBm1926189217))

(d)       Effects on the Engine

CS-E 510 defines the Hazardous Engine Effects for turbine
Engines.

CS-E 50(g) is primarily intended to address the effects of
aircraft signals, such as aircraft air data information, or other signals
which could be common to all Engine Control Systems in a multi-Engine
installation. The control system design should ensure that the full-up system
is capable of providing the declared minimum rated thrust or power throughout
the Engine operating envelope.

CS-E 50(g) requires the applicant to provide an analysis of
the effect of loss or corruption of aircraft data on Engine thrust or power.
The effects of Failures in Aircraft-Supplied Data should be documented in the
SSA as described in Section (8) above. Where appropriate, aircraft data
Failures or malfunctions that contribute to LOTC/LOPC events should be
included in the LOTC/LOPC analysis.

(e)       Validation

Functionality of the Fault Accommodation logic should be
demonstrated by test, analysis, or combination thereof. In the case where the
aircraft air data system is not functional because of the loss of all aircraft
generated power, the Engine Control System should include validated Fault
Accommodation logic which allows the Engine to operate acceptably with the
loss of all aircraft-supplied air data. Engine operation in this system
configuration should be demonstrated by test.

For all dispatchable Control Modes, see CS-E 1030 and AMC E
1030.

If an Alternate Mode, independent of Aircraft-Supplied Data,
has been provided to accommodate the loss of all data, sufficient testing
should be conducted to demonstrate that the operability specifications have
been met when operating in this mode. Characteristics of operation in this
mode should be included in the instructions for installation and operation as
appropriate. This Alternate Mode need not be dispatchable.

(13)     AIRCRAFT SUPPLIED
ELECTRICAL POWER

(a)       Objective

The objective is to provide an electrical
power source that is single Fault tolerant (including common cause or mode) in
order to allow the EECS to comply with CS-E 50(c)(2). The most common practice
for achieving this objective has been to provide a dedicated electrical power
source for the EECS. When aircraft electrical power is used, the assumed
quality and reliability levels of this aircraft power should be contained in
the instructions for installation.

(b)       Electrical
power sources

An Engine dedicated power source is defined
herein as an electric power source providing electrical power generated and
supplied solely for use by a single Engine Control System. Such a source is
usually provided by an alternator(s), mechanically driven by the Engine or the
transmission system of rotorcraft. However, with the increased integration of
the Engine-aircraft systems and with the application of EECS to small Engines,
both piston and turbine, use of an Engine-mounted alternator may not necessarily
be the only design approach for meeting the objective.

Batteries are considered an
Aircraft-Supplied Power source except in the case of piston Engines. For
piston Engines, a battery source dedicated solely to the Engine Control System
may be accepted as an Engine dedicated power source. In such applications,
appropriate information for the installer should be provided including, for
example, health status and maintenance requirements for the dedicated battery
system.

An analysis and a review of the design
architecture should identify the requirements for Engine dedicated power
sources and Aircraft-Supplied Power sources. The analysis should include the
effects of losing these sources. If the Engine is dependent on Aircraft-Supplied
Power for any operational functions, the analysis should result in a
definition of the requirements for Aircraft-Supplied Power.

The following configurations have been used:

—
EECS dependent on Aircraft-Supplied Power

—
EECS independent of Aircraft-Supplied Power
(Engine dedicated power source)

—
Aircraft-Supplied Power used for functions,
switched by the EECS

—
Aircraft-Supplied Power directly used for
Engine functions, independently from the EECS

—
Aircraft-Supplied Power used to back up the
Engine dedicated power source

The capacity of any Engine dedicated power
source, required to comply with CS-E 50(h)(2), should provide sufficient
margin to maintain confidence that the Engine Control System will continue to
function in all anticipated Engine operating conditions where the control
system is designed and expected to recover Engine operation automatically
in-flight. The autonomy of the Engine Control System should be sufficient to
ensure its functioning in the case of immediate automatic relight after
unintended shutdown. Conversely, the autonomy of the Engine Control System in
the whole envelope of restart in windmilling conditions is not always
required. This margin should account for any other anticipated variations in
the output of the dedicated power source such as those due to temperature
variations, manufacturing tolerances and idle speed variations. The design
margin should be substantiated by test and/or analysis and should also take
into account any deterioration over the life of the Engine.

(d)       Aircraft-Supplied
Power Reliability

Any Aircraft-Supplied Power reliability
values used in system analyses, whether supplied by the aircraft manufacturer
or assumed, should be contained in the instructions for installation.

When Aircraft-Supplied Power is used in any
architecture, if aircraft power Faults or Failures can contribute to LOTC/LOPC
or Hazardous Engine Effects, these events should be included in the Engine SSA
and LOTC/LOPC analyses.

When compliance with CS-E 50(h)(1) imposes
an Engine dedicated power source, Failure of this source should be addressed
in the LOTC/LOPC analysis required under CS-E 50 (c). While no credit is
normally necessary to be given in the LOTC/LOPC analysis for the use of
Aircraft-Supplied Power as a back-up power source, Aircraft-Supplied Power has
typically been provided for the purpose of accommodating the loss of the
Engine dedicated power source. However, LOTC/LOPC allowance and any impact on
the SSA for the use of Aircraft-Supplied Power as the sole power source for an
Engine control Back-up System or as a back-up power source would be reviewed
on a case-by-case basis.

In some system architectures, an Engine
dedicated power source may not be required and Aircraft-Supplied Power may be
acceptable as the sole source of power.

An example is a system that consists of a
primary electronic single channel and a full capability hydromechanical
Back-up System that is independent of electrical power (a full capability
hydromechanical control system is one that meets all CS-E specifications and
is not dependent on aircraft power). In this type of architecture, loss or
interruption of Aircraft-Supplied Power is accommodated by transferring
control to the hydromechanical system. Transition from the electronic to the
hydromechanical control system is addressed under CS-E 50(b).

Another example is an EECS powered by an
aircraft power system that could support a critical fly-by-wire flight control
system. Such a power system may be acceptable as the sole source of power for
an EECS. In this example, it should be stated in the instructions for
installation that a detailed design review and safety analysis is to be
conducted to identify latent failures and common cause failures that could
result in the loss of all electrical power. The instructions should also state
that any emergency power sources must be known to be operational at the
beginning of the flight. Any emergency power sources must be isolated from the
normal electrical power system in such a way that the emergency power system
will be available no matter what happens to the normal generated power system.
If batteries are the source of emergency power, there must be a means of
determining their condition prior to flight, and their capacity must be shown
to be sufficient to assure exhaustion will not occur before getting the aircraft
safely back on the ground.

This will satisfy that appropriate
reliability assumptions are provided to the installer.

(e)       Aircraft-Supplied
Power Quality

When Aircraft-Supplied Power is necessary
for operation of the Engine Control System, CS-E 50(h)(3) specifies that the
Engine instructions for installation contain the Engine Control System’s
electrical power supply quality requirements. This applies to any of the
configurations listed in paragraph (13)(c) or any new configurations or novel
approach not listed that use Aircraft-Supplied Power. These quality
requirements should include steady state and transient under-voltage and
over-voltage limits for the equipment. The power input standards of RTCA
DO-160/EUROCAE ED-14 are considered to provide an acceptable definition of
such requirements. If RTCA DO-160/EUROCAE ED-14 is used, any exceptions to the
power quality standards cited for the particular category of equipment
specified should be stated.

It is recognised that the electrical or
electronic components of the Engine Control System when operated on
Aircraft-Supplied Power may cease to operate during some low voltage aircraft
power supply conditions beyond those required to sustain normal operation, but
in no case should the operation of the Engine control result in a Hazardous
Engine Effect. In addition, low voltage transients outside the control
system’s declared capability should not cause permanent loss of function of
the control system, or result in inappropriate control system operation which
could cause the Engine to exceed any operational limits, or cause the
transmission of unacceptable erroneous data.

When aircraft power recovers from a
low-voltage condition to a condition within which the control system is
expected to operate normally, the Engine Control System should resume normal
operation. The time interval associated with this recovery should be contained
in the Engine instructions for installation. It is recognised that
Aircraft-Supplied Power conditions may lead to an Engine shutdown or Engine
condition which is not recoverable automatically. In these cases the Engine
should be capable of being restarted, and any special flight crew procedures
for executing an Engine restart during such conditions should be contained in
the Engine instructions for operation. The acceptability of any
non-recoverable Engine operating conditions - as a result of these
Aircraft-Supplied Power conditions - will be determined at aircraft
certification.

If Aircraft-Supplied Power supplied by a
battery is required to meet an "all Engines out" restart
requirement, the analysis according to paragraph 13(c) should result in a
definition of the requirements for this Aircraft-Supplied Power. In any installation
where aircraft electrical power is used to operate the Engine Control System,
such as low Engine speed in-flight re-starting conditions, the effects of any
aircraft electrical bus-switching transients or power transients associated
with application of electrical loads, which could cause an interruption in
voltage or a decay in voltage below that level required for proper control functioning,
should be considered.

(f)        Effects on the Engine

Where loss of aircraft power results in a
change in Engine Control Mode, the Control Mode transition should meet the
specifications of CS-E 50(b).

For some Engine control functions that rely
exclusively upon Aircraft-Supplied Power, the loss of electrical power may
still be acceptable. Acceptability is based on evaluation of the change in
Engine operating characteristics, experience with similar designs, or the
accommodation designed into the control system.

Examples of such Engine control functions
that have traditionally been reliant on aircraft power include:

—
Engine start and ignition

—
Thrust Reverser deployment

—
Anti-Icing (Engine probe heat)

—
Fuel Shut-Off

—
Over-speed Protection Systems

—        Non-critical functions that are
primarily performance enhancement functions which, if inoperative, do not
affect the safe operation of the Engine.

(g)       Validation

The applicant should demonstrate the effects
of loss of Aircraft-Supplied Power by Engine test, system validation test or
bench test or combination thereof.

(14)     PISTON ENGINES

Piston Engines are addressed by the sections above; no
additional specific guidance is necessary.

CS-E 50 specifications are applicable to these Engines but,
when interpretation is necessary, the conditions which would be acceptable for
the aircraft installation should be considered.

(15)     ENGINE, PROPELLER AND
AIRCRAFT SYSTEMS INTEGRATION AND THE INTERRELATION BETWEEN ENGINE, PROPELLER
AND AIRCRAFT CERTIFICATION ACTIVITIES

(a)       Aircraft or Propeller Functions
Integrated into the Engine Control System

This involves the integration of aircraft or Propeller
functions (i.e., those that have traditionally not been considered Engine
control functions), into the Electronic Engine Control System’s hardware and
software.

Examples of this include thrust reverser control systems,
Propeller speed governors, which govern speed by varying pitch, and ATTCS.
When this type of integration activity is pursued, the EECS becomes part of -
and should be included in the aircraft’s SSA, and although the aircraft
functions incorporated into the EECS may receive review at Engine
certification, the acceptability of the safety analysis involving these
functions should be determined at aircraft certification.

The EECS may be configured to contain only part of the
aircraft system’s functionality, or it may contain virtually all of it. Thrust
reverser control systems are an example where only part of the functionality
is included in the EECS. In such cases, the aircraft is configured to have
separate switches and logic (i.e., independent from the EECS) as part of the
thrust reverser control system. This separation of reverser control system
elements and logic provides an architectural means to limit the criticality of
the functions provided by the EECS.

However, in some cases the EECS may be configured to
incorporate virtually all of a critical aircraft function. Examples of this
“virtual completeness” in aircraft functionality are EECS which contain full
authority to govern Propeller speed in turboprop powered aircraft and ATTCS in
turbofan power aircraft.

The first of these examples is considered critical because,
if an Engine fails, the logic in the Engine Control System should be
configured to feather the Propeller on that Engine. Failure to rapidly feather
the Propeller following an Engine Failure results in excessive drag on the
aircraft, and such a condition can be critical to the aircraft. When functions
like these are integrated into the Engine control such that they render an
EECS critical, special attention should be paid to assuring that no single (including
common cause/mode) Failures could cause the critical Failure condition, e.g.
exposure of the EECS to overheat should not cause both an Engine shutdown and
Failure of the Propeller to feather.

The second example, that of an ATTCS, is considered critical
because the system is required to increase the thrust of the remaining
Engine(s) following an Engine Failure during takeoff, and the increased thrust
on the remaining Engines is necessary to achieve the required aircraft
performance.

All of the above examples of integration involve aircraft
functionality that would receive significant review during aircraft
certification.

(b)       Integration of Engine Control Functions
into Aircraft Systems

The trend toward systems integration may lead to aircraft
systems performing functions traditionally considered part of the Engine
Control System. Some designs may use aircraft systems to implement a
significant number of the Engine Control System functions. An example would be
the complex integrated flight and Engine Control Systems – integrated in
aircraft avionics units - which govern Engine speed, rotor speed, rotor pitch
angle and rotor tilt angle in tilt-rotor aircraft.

In these designs, aircraft systems may be required to be used
during Engine certification. In such cases, the Engine applicant is
responsible for specifying the requirements for the EECS in the instructions
for installation and substantiating the adequacy of those requirements.

An example of limited integration would be an Engine control
which receives a torque output demand signal from the aircraft and responds by
changing the Engine’s fuel flow and other variables to meet that demand.
However, the EECS itself, which is part of the type design, provides all the
functionality required to safely operate the Engine in accordance with CS-E or
other applicable specifications.

(i)        Objective

To satisfy the aircraft specifications, such as CS 25.901, CS
25.903 and CS 25.1309, an analysis of the consequences of Failures of the
Engine Control System on the aircraft has to be made. The Engine applicant
should, together with the aircraft applicant, ensure that the software/AEH
criticality levels and the safety and reliability objectives for the Engine
electronic control system are consistent with these specifications.

(ii)       Interface Definition and System
Responsibilities

System responsibilities as well as interface definitions
should be identified for the functional as well as hardware and software
aspects between the Engine, Propeller and the aircraft systems in the
appropriate documents.

The Engine/Propeller/aircraft documents should cover in
particular:

—
Functional requirements and criticality (which
may be based on Engine, Propeller and aircraft considerations);

—
Fault Accommodation strategies;

—
Maintenance strategies;

—
The software/AEH criticality level (per
function if necessary);

—
The reliability objectives for:

—
LOTC/LOPC events,

—
Transmission of faulty parameters;

—
The environmental requirements including the
degree of protection against lightning or other electromagnetic effects (e.g.
level of induced voltages that can be supported at the interfaces);

—
Engine, Propeller and aircraft interface data
and characteristics;

—
Aircraft power supply requirements and
characteristics (if relevant).

(iii)      Distribution of Compliance Tasks

The tasks for the certification of the aircraft propulsion
system equipped with Electronic Engine Control Systems (EECSs) may be shared
between the Engine, Propeller and aircraft applicants. The distribution of
these tasks between the applicants should be identified and agreed with the
appropriate Engine, Propeller and aircraft authorities. For further
information refer to [AMC 20-1()](#_DxCrossRefBm1926189217).

The aircraft certification should deal with the overall
integration of the Engine and Propeller in compliance with the applicable
aircraft specifications.

The Engine certification will address the functional aspects
of the Engine Control System in compliance with the applicable Engine
specifications.

Appropriate evidence provided for Engine certification should
be used for aircraft certification. For example, the quality of any aircraft
function software/AEH and aircraft–Engine interface logic already demonstrated
for Engine certification should need no additional substantiation for aircraft
certification.

Two examples are given below to illustrate this principle.

(A)      Case
of an EECS performing the functions for the control of the Engine and the
functions for the control of the Propeller.

The Engine certification would address all general
requirements such as software/AEH development assurance procedures, EMI, HIRF
and lightning protection levels, effects of loss of aircraft-supplied power.

The Engine certification would address the functional aspects
for the Engine functions (safety analysis, rate of LOTC/LOPC events, effect of
loss of aircraft-supplied data, etc.). The Fault Accommodation logic affecting
the control of the Engine, for example, will be reviewed at that time.

The Propeller certification will similarly address the
functional aspects for the Propeller functions. The Fault Accommodation logic
affecting the control of the Propeller, for example, will be reviewed at that
time.

In this example, the Propeller functions and characteristics
defined by the Propeller applicant, which are to be provided by the Engine
Control System, would normally need to be refined by flight test. The
Propeller applicant is responsible for ensuring that these functions and
characteristics, which are provided for use during the Engine certification
programme, define an airworthy Propeller configuration, even if they have not
yet been refined by flight test.

With regard to changes in design, agreement by all parties
involved should be reached so that changes to the Engine Control System that
affect the Propeller system, or vice versa, do not lead to any inadvertent
effects on the other system.

(B)       Case
of an aircraft computer performing the functions for the control of the
Engine.

The aircraft certification will address all general
requirements such as software/AEH development assurance procedures, EMI, HIRF
and lightning protection levels.

The aircraft certification will address the functional
aspects for the aircraft functions.

The Engine certification will address the functional aspects
for the Engine functions (safety analysis, rate of LOTC/LOPC events, effect of
loss of aircraft-supplied data, etc.) The Fault Accommodation logic affecting
the control of the Engine, for example, will be reviewed at that time.

[Amdt 20/2]

[Amdt 20/10]

[Amdt 20/19]

Compare / EASA/ Incorporated Amendments/ Compare & Highlight Differences

AMC 20-3B Certification of Engines Equipped with Electronic Engine Control Systems

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