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MG 23  Automatic Flight Guidance and Control Systems (AFGCS) installation in CS-27 Rotorcraft

ED Decision 2018/015/R15/R

This AMC provides further guidance and acceptable means of compliance to supplement FAA AC 27-1B Change 7 MG 23, which is the EASA acceptable means of compliance, as provided for in AMC 27 General. However, some aspects of the FAA AC are deemed by EASA to be at variance with EASA’s interpretation or its regulatory system. EASA’s interpretation of these aspects is described below. Paragraphs of FAA AC 27-1B Change 7 MG 23 that are not amended below are considered to be EASA acceptable means of compliance.

a.       Purpose.

(1)      The following Radio Technical Commission for Aeronautics (RTCA) documents are considered to be guidance for showing compliance with the relevant certification specifications for the installation of automatic flight control guidance and control systems (AFGCS).

(i)       RTCA Document DO-325, Minimum Operational Performance Standards (MOPS) for Automatic Flight Guidance and Control Systems and Equipment, issued 8 December 2010.

(ii)      RTCA Document DO-336, Guidance for Certification of Installed Automatic Flight Guidance and Control Systems (AFGCS) for Part 27/29 Rotorcraft, issued 21 March 2012.

(2)     RTCA Document DO-325 contains the minimum operational performance standards (MOPS) for AFGCS equipment.

         DO-336 provides guidance on the certification of AFGCS in rotorcraft. It invokes parts of DO-325 as the performance standards that are applicable for the installation of AFGCS equipment in rotorcraft. It provides guidance on conducting a safety assessment. Lastly, DO-336 provides lists of the regulations that can be applicable to an AFGCS installation, and potential methods of compliance with those regulations.

(3)      The guidance contained in DO-336 and DO-325 is not mandatory and provides guidance for showing compliance with the applicable provisions of CS-27.

         Note: following this guidance alone does not guarantee acceptance by EASA. EASA may require additional substantiation or design changes as a basis for finding compliance.

b.       Guidance for the use of RTCA Documents DO-325 and DO-336.

RTCA Document DO-336 has two primary focus items: to highlight the requirements for a proper safety assessment (Chapter 8) and the compliance demonstration (Chapter 9).

Note: each of these should be discussed with EASA very early in the certification programme, and included in the certification plan.

c.       References.

(1)      CS-27 provisions

Paragraph

Title

27.671

General. (Control Systems)

27.672

Stability augmentation, automatic, and power-operated systems.

27.1309

Equipment, systems, and installations.

27.1329

Automatic pilot system.

27.1335

Flight director systems.

Appendix B to CS-27

Airworthiness Criteria for Helicopter Instrument Flight

 

(2)      AMC/ACs (available at http://rgl.faa.gov/ or https://www.easa.europa.eu/document-library/certification-specifications/group/amc-20-general-acceptable-means-of-compliance-for-airworthiness-of-products-parts-and-appliances#group-table)

AMC/AC

Title

20-115D

Airborne Software Development Assurance Using EUROCAE ED-12 and RTCA DO-178

20-138D

Airworthiness Approval of Positioning and Navigation Systems

20-152

RTCA, Inc., Document RTCA/DO-254, Design Assurance Guidance for Airborne Electronic Hardware.

21-50

Installation of TSOA Articles and LODA Appliances

27-1B Section 27.671

Control Systems - General.

27-1B, Section 27.672

Stability Augmentation, Automatic, and Power-Operated Systems.

27-1B, Section 27.1309

Equipment, Systems, and Installations.

27-1B, Section 27.1329

Automatic Pilot System.

27-1B, Section 27.1335

Flight Director Systems.

 

(3)      Industry standards (RTCA documents are available at www.rtca.org and SAE international documents are available at www.sae.org):

Document

Title

RTCA/ DO-178

Software Considerations in Airborne Systems and Equipment Certification

RTCA/ DO-254

Design Assurance Guidance for Airborne Electronic Hardware

RTCA/ DO-325

Minimum Operational Performance Standards (MOPS) for Automatic Flight Guidance and Control Systems and Equipment, issued December 8, 2010.

RTCA/ DO-336

Guidance for Certification of Installed Automatic Flight Guidance and Control Systems (AFGCS) for Part 27/29 Rotorcraft, issued March 21, 2012.

SAE, International ARP 4754A

Certification considerations for highly-integrated or complex aircraft systems

SAE, International ARP 4761

Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment

 

[Amdt No: 27/6]


[1]      The published date represents the date when the consolidated version of the document was generated.

[2]      Euro-Lex, Important Legal Notice: http://eur-lex.europa.eu/content/legal-notice/legal-notice.html.

[3]      It should be noted that rotorcraft tend to have a high centre of gravity due to the position of the engines and gearbox on top of the cabin. It therefore follows that most of the ballast is likely to be required to be installed in these high locations of the model.

[4]      Rotors touching the waves can promote capsize, but they can also be a stabilising factor depending on the exact circumstances. Furthermore, rotor blades are often lost during the ditching due to contact with the sea. It is therefore considered acceptable to omit them from the model.

[5]      In general the model cannot be permitted to float freely in the basin because in the necessarily long-wave test durations, the model would otherwise drift down the basin and out of the calibrated wave region. Constraining the model to remain beam-on to the waves and not float freely is regarded as a conservative approach to the capsize test. A free-floating test is optional after a specific capsize event, in order to investigate whether the restraint system contributed to the event. It may also be possible to perform a complete free-floating test campaign by combining many short exposures in a wave basin capable of demonstrating a large calibrated wave region.

[6]      A sea anchor deployed from the rotorcraft nose is intended to improve stability by keeping the rotorcraft nose into the waves. However, such devices take a significant time to deploy and become effective, and so, their beneficial effect is to be ignored. The rotorcraft model will be restrained to remain beam-on to the waves.

[7]      Wind generally has a tendency to redirect the rotorcraft nose into the wind/waves, thus reducing the likelihood of capsize. Therefore, this conservative testing approach does not include a wind simulation.

[8]      Each 5-minute exposure might not be independent if, for example, there was flooding of the rotorcraft, progressively degrading its stability. However, in this context, it is considered that the assumption of independence is conservative.

[9]      Council Directive 89/686/EEC of 21 December 1989 on the approximation of the laws of the Member States relating to personal protective equipment (OJ L 399, 30.12.1989, p. 18).

[10]    Regulation (EU) 2016/425 of the European Parliament and of the Council of 9 March 2016 on personal protective equipment and repealing Council Directive 89/686/EEC (OJ L 81, 31.3.2016, p. 51).

[11]    See reference in AMC 27 General

[12]    Commission Regulation (EU) No 965/2012 of 5 October 2012 laying down technical requirements and administrative procedures related to air operations pursuant to Regulation (EC) No 216/2008 of the European Parliament and of the Council (OJ L 296, 25.10.2012, p. 1).

[1]      The published date represents the date when the consolidated version of the document was generated.

[2]      Euro-Lex, Important Legal Notice: http://eur-lex.europa.eu/content/legal-notice/legal-notice.html.

[3]      It should be noted that rotorcraft tend to have a high centre of gravity due to the position of the engines and gearbox on top of the cabin. It therefore follows that most of the ballast is likely to be required to be installed in these high locations of the model.

[4]      Rotors touching the waves can promote capsize, but they can also be a stabilising factor depending on the exact circumstances. Furthermore, rotor blades are often lost during the ditching due to contact with the sea. It is therefore considered acceptable to omit them from the model.

[5]      In general the model cannot be permitted to float freely in the basin because in the necessarily long-wave test durations, the model would otherwise drift down the basin and out of the calibrated wave region. Constraining the model to remain beam-on to the waves and not float freely is regarded as a conservative approach to the capsize test. A free-floating test is optional after a specific capsize event, in order to investigate whether the restraint system contributed to the event. It may also be possible to perform a complete free-floating test campaign by combining many short exposures in a wave basin capable of demonstrating a large calibrated wave region.

[6]      A sea anchor deployed from the rotorcraft nose is intended to improve stability by keeping the rotorcraft nose into the waves. However, such devices take a significant time to deploy and become effective, and so, their beneficial effect is to be ignored. The rotorcraft model will be restrained to remain beam-on to the waves.

[7]      Wind generally has a tendency to redirect the rotorcraft nose into the wind/waves, thus reducing the likelihood of capsize. Therefore, this conservative testing approach does not include a wind simulation.

[8]      Each 5-minute exposure might not be independent if, for example, there was flooding of the rotorcraft, progressively degrading its stability. However, in this context, it is considered that the assumption of independence is conservative.

[9]      Council Directive 89/686/EEC of 21 December 1989 on the approximation of the laws of the Member States relating to personal protective equipment (OJ L 399, 30.12.1989, p. 18).

[10]    Regulation (EU) 2016/425 of the European Parliament and of the Council of 9 March 2016 on personal protective equipment and repealing Council Directive 89/686/EEC (OJ L 81, 31.3.2016, p. 51).

[11]    See reference in AMC 27 General

[12]    Commission Regulation (EU) No 965/2012 of 5 October 2012 laying down technical requirements and administrative procedures related to air operations pursuant to Regulation (EC) No 216/2008 of the European Parliament and of the Council (OJ L 296, 25.10.2012, p. 1).

Details
Source-Title: MG 23 Automatic Flight Guidance and Control Systems (AFGCS) installation in CS-27 Rotorcraft View latest amendments
Erulesid: ERULES-1963177438-11638 Compare versions
Domain: Initial airworthiness
Amendedby: Amendment 6
Applicabilitydate: 18 December, 2018
Entryintoforcedate: 18 December, 2018
Regulatorysource: ED Decision 2018/015/R Navigate
Regulatorysubject: CS-27
Typeofcontent: GM to CS (Guidance material to certification specification)
Origin: EASA
Category: EAR