AMC5 FSTD(H).300  Guidance on design and qualification of helicopter flight and navigation procedures trainers (FNPTs)

Decision 2012/011/R

(a)     Basic philosophy

(1)     Traditionally training devices used by the ab-initio professional pilot schools have been relatively simple instrument flight-only aids. These devices were loosely based on the particular school’s helicopter. The performance would be approximately correct in a small number of standard configurations; however, the handling characteristics could range from rudimentary to loosely representative. The instrumentation and avionics fit varied between a basic fit and one very close to the target helicopter. The approval to use such devices as part of a training course was based on a regular subjective evaluation of the equipment and its operator by an inspector of the competent authority.

(2)     The FNPT I is essentially a replacement for the traditional instrument flight ground training device. The FNPT II and FNPT III are more sophisticated standards and each fulfil the wider requirements of the various Part-FCL professional pilot training modules up to and including (optionally with additional features) multi-crew cooperation (MCC) training.

(3)     The currently available technology enables such devices to have much greater capabilities and lower life-cycle costs than was previously possible. A more objective design basis encourages better understanding and therefore better modelling of helicopter systems, handling and performance. These advances combined with the costs of flying and with the environmental pressures all point towards the need for FNPT standards.

(b)     Design standards

Five sets of design standards are specified within CS-FSTD(H): FNPT I, II, II MCC, III and III MCC.

(1)     Simulated helicopter configuration

Unlike FFSs and FTDs, FNPTs are not primarily intended to be representative of a specific type of helicopter (although they may in fact be type-specific if desired).

The configuration chosen should sensibly represent the helicopter or helicopters likely to be used as part of the overall training package. Areas such as general layout, seating, instruments and avionics, control type, control force and position, performance and handling and powerplant configuration should be representative of the class of helicopters or the helicopter itself.

Note: throughout this document, the term “helicopter” is used to represent the aircraft being modelled which can be a specific helicopter type, a family of similar helicopter types or a totally generic helicopter.

It would be beneficial for all parties involved in the acquisition of an FNPT to engage in early discussions with the competent authority to broadly agree a suitable device configuration. Ideally, any such discussion would take place in time to avoid any delays in the design/build/acceptance process thereby ensuring a smooth entry into service.

The configuration chosen should be sensibly representative of the “helicopter” likely to be used as part of the overall training package, especially in areas such as general cockpit layout, seating, instruments and avionics, flying controls control forces and positions, performance, handling and powerplant.

(2)     The cockpit

The cockpit should be representative of the “helicopter”. The controls, instruments and avionics controllers should be representative in touch, feel, layout, colour and lighting to create a positive learning environment and good transfer of training to the helicopter. For good training ambience the cockpit of the FNPT I should be sufficiently enclosed to exclude any distractions. For both FNPT IIs and IIIs the cockpit should be fully enclosed. Distractions arising from external sources, which may affect the student’s concentration or may denigrate the effects of the simulation, should be avoided. Thus in the case of an FNPT I, if the rear of the device is open, it would be inappropriate to install this type of device in a non-enclosed room or in an area where several such devices are located. Were this to be permitted, the activities in one device may affect those in an adjacent one. If the device is to be installed in an area shared by other devices then the rear of the cockpit including the instructor’s station should be fully enclosed, and this enclosure should extend to include the roof. In the case of the FNPT II and III the same interpretations should apply but an additional consideration is that the performance of the visual system will be adversely affected by any light ingress or reflections. It follows that it would not be necessary to have a fully enclosed structure at the rear of the cockpit were the FNPT to be installed in a separate room.

(3)     Cockpit components

As with any training device, the components used within the cockpit area do not need to be aircraft parts; however, any parts used should be representative and should be robust enough to endure the training tasks. With the current state of technology the use of simple CRT/LCD monitor-based representations and touch screen controls would be acceptable. The training tasks envisaged for these devices are such that appropriate layout and feel is very important: i.e. the altimeter sub-scale knob needs to be physically located on the altimeter.

The use of CRT/LCDs with physical overlays incorporating operational switches/knobs/buttons replicating a helicopter instrument panel may be acceptable to the competent authority.

(4)     Data

The data used to model the aerodynamics, flight controls and engines should be soundly based on a helicopter. It is not acceptable and would not give good training if the models merely represented a few key configurations bearing in mind the extent of the potential credits available. Validation data may be derived from a specific helicopter within a family of helicopters that the FNPT is intended to represent, or it may be based on information from several helicopters within a family. It is recommended that the intended validation data together with a substantiation report be submitted to the competent authority for review.

(i)      Data collection and model development

         Recognising the cost and complexity of flight simulation models, it should be possible to generate generic family “typical” models. Such models should be continuous and vary sensibly throughout the required training flight envelope. A basic requirement for any modelling is the integrity of the mathematical equations and models used to represent the flying qualities and performance of the designated helicopter configuration simulated. Data to tune the generic model to represent a more specific helicopter can be obtained from many sources without recourse to expensive flight test such as:

(A)     helicopter design data;

(B)     flight and maintenance manuals; or

(C)     observations on ground and in air.

Data obtained on the ground and in flight can be measured and recorded using a range of simple means such as:

(A)     video;

(B)     pencil and paper;

(C)     stopwatch;

(D)     new technologies.

Any such data gathering should take place at representative masses and centres of gravity. Development of such a data set including justification and the rationale for the design and intended performance, the measurement methods and recorded parameters (e.g. mass, CG, atmospheric conditions) should be carefully documented and available for inspection by the competent authority as part of the qualification process.

(5)     Limitations

In helicopters, varied and different flight control configurations can be found: with and without servo-control assistance, with and without artificial feel trim control forces, trim control release and automatic trim. As a consequence, simulation of the flight control forces should take into account user requirements in order to define the optimum solution in an effort to simplify the control loading requirements.

It should be remembered however that whilst a simple model may be sufficient for the task, it is vitally important that negative characteristics are not present.

(c)      Latency and visual

(1)     There are two methods of establishing latency, which is the relationship between the controls and the visual system, cockpit instruments response and initial motion system response, if fitted. These should be coupled closely to provide integrated sensory cues.

(2)     For a generic FNPT, a transport delay test is the only suitable test which demonstrates that the FNPT system does not exceed the permissible delay. If the FNPT is based upon a particular helicopter type, either transport delay or response time tests are acceptable. Response time tests check that the response to abrupt pitch, roll, and yaw inputs at the pilot's position is within the permissible delay, but not before the time when the “helicopter” would respond under the same conditions. Visual scene changes from steady state disturbance should occur within the system dynamic response limit (but not before the resultant motion onset if fitted).

(3)     The transport delay test should measure all the delay encountered by a step signal migrating from the pilot’s control, through the control loading electronics (if applicable) and interfacing through all the simulation software modules in the correct order, using a handshaking protocol, finally through the normal output interfaces to the visual system and instrument displays. A recordable start time for the test should be provided by a pilot flight control input. The test mode should permit normal computation time to be consumed and should not alter the flow of information through the hardware/software system.

(4)     The transport delay of the system is the time between control input and the individual hardware responses. It needs only to be measured once in each axis.

(5)     Care should be taken when using the limited processing power of the lower cost visual systems to concentrate on the key areas that support the intended uses, thereby avoiding compromising the visual model by including unnecessary features e.g. moving ground traffic, marshallers. The capacity of the visual model should be directed towards:

(i)      runway/operating site surface;

(ii)     runway/operating site lighting systems;

(iii)     approach guidance aids and lighting systems;

(iv)     touch down and lift-off (TLOF) and final approach and take-off (FATO) areas;

(v)      detailed ground features where credits are required for navigation training; and

(vi)     basic environmental lighting (night/dusk).

(d)     Motion

Although motion is not a requirement for an FNPT, should the FSTD operator choose to have one fitted, it should be evaluated to ensure that its contribution to the overall fidelity of the device is not negative. Unless otherwise stated in this document, the motion requirements are as specified for a level A FFS, see AMC2 FSTD(H).300.

(1)     For level A FFSs, the requirements for both the primary cueing and buffet simulation have been not specified in detail. Traditionally, for primary cueing, emphasis has been laid on the numbers of axes available on the motion system. For this level of FFS, it is felt appropriate that the simulator manufacturer should be allowed to decide on the complexity of the motion system. However, during the evaluation, the motion system should be assessed subjectively to ensure that it is supporting the piloting task, including engine failures, and is in no way providing negative cueing.

(2)     Buffet simulation is important to add realism to the overall simulation; for level A, the effects can be simple but they should be appropriate, in harmony with the sound cues and in no way providing negative training.

(3)     The motion system transport delay should meet the standards prescribed for the visual display and cockpit instrument response.

(e)     Testing/evaluation

(1)     General

The FNPT should be assessed in those areas that are essential to completing the pilot training, testing and checking process. This includes the FNPT's longitudinal and lateral directional responses, specific operations, control checks, cockpit, and instructor station functions checks, and certain additional requirements depending on the complexity or qualification level of the FNPT. The visual system (where applicable) should be evaluated against tests contained in the table of validation tests (AMC1 FSTD(H).300).

To ensure that any device meets its design criteria, initially and periodically throughout its life a system of objective and subjective testing should be used. The subjective and objective testing methodology should be similar to that in use for FFS.

The validation tests specified (AMC1 FSTD(H).300, (b)(3)) can be “flown” by a suitably skilled person and the results recorded manually. Bearing in mind the cost implications, the use of automatic recording (and testing) is encouraged thereby increasing the repeatability of the achieved results but any such automatic test shall be capable of being rerun by manually flying the test.

The tolerances specified are designed to ensure that the device meets its original target criteria year after year. It is therefore important that such target data is carefully derived and values are agreed with the appropriate inspecting authority in advance of any formal qualification process. For initial qualification, it is highly desirable that the device should meet its design criteria within the listed tolerances, however unlike the tolerances specified for FFS, the tolerances contained within this document are specifically intended to be used to ensure repeatability during the life of the device and in particular at each recurrent regulatory inspection.

(2)     Validation tests

The intent is to evaluate the FNPT as objectively as possible. Pilot acceptance, however, is also an important consideration. Therefore, the FNPT should be subjected to validation, and functions and subjective tests listed in (AMC1 FSTD(H).300). Validation tests are used to compare objectively FNPT performances against validation data to ensure that they agree within design tolerances acceptable to the competent authority. Functions and subjective tests provide a basis for evaluating FNPT capability to perform over a typical training period, determining that the FNPT satisfactorily meets each stated training objective and competently simulates each training manoeuvre or procedure and to verify correct operation of the FNPT.

The design data may be derived from flight test data, manufacturer’s design data, information from an aircraft flight manual and maintenance manuals, results of approved or commonly accepted simulations or predictive models, recognised theoretical results, information from the public domain, or other sources as deemed necessary by the FNPT manufacturer to be representative of a helicopter.

The use of CT&M is not to be taken as an indication that certain areas of simulation can be ignored. For such tests, the performance of the device should be appropriate and representative of the “helicopter” configuration and should under no circumstances exhibit negative characteristics. Where CT&M is used, it is strongly recommended that an automatic recording system be used to "footprint" the baseline results thereby avoiding the effects of possible divergent subjective opinions during recurrent evaluations.

(3)     Subjective tests

The subjective tests listed under “Functions and subjective tests” (AMC1 FSTD(H).300) should be flown out by a suitably qualified and experienced pilot.

Subjective testing should review not only the interaction of all of the systems but the integration of the FNPT with:

(i)      the training environment;

(ii)     freezes and repositions;

(iii)     nav-aid environment;

(iv)     communications;

(v)      weather and visual scene contents.

(4)     Initial qualification

For initial qualification testing of FNPTs validation data should be used. They may be derived from a specific helicopter or they may be based on information from several helicopters within the group of helicopters. The substantiation of the set of data used to build the validation data should be in the form of an engineering report and should show that the proposed validation data are representative of a helicopter. With the concurrence of the competent authority, it may be in the form of a manufacturer’s previously approved set of validation data for the applicable FNPT. Once the set of data for a specific FNPT has been accepted and approved by the competent authority, it should become the validation data to be used as reference for subsequent recurrent evaluations.

For FNPT initial qualification, the tolerances listed for parameters in the validation list table (AMC1 FSTD(H).300) should be replaced by ‘correct trend and magnitude’ (CT&M) and the FNPT should be tested and assessed as representative of a helicopter to the satisfaction of the competent authority.

Tolerances listed for parameters in the validation tests table (AMC1 FSTD(H).300) should not be confused with FNPT design tolerances. Validation test tolerances are the maximum acceptable for FNPT recurrent qualification testing.

FSTD operators seeking initial or upgrade evaluation of an FNPT should be aware that performance and handling data for older helicopters may not be of sufficient quality to meet some of the test standards contained in this AMC. In this instance it may be necessary for an FSTD operator to acquire additional design and/or validation data.

During FNPT evaluation, if a problem is encountered with a particular FSTD validation test, the test may be repeated to ascertain if the problem was caused by test equipment or FSTD operator error. Following this, if the test problem persists during initial FNPT evaluation, an FSTD operator should be prepared to offer alternative test results which relate to the test in question.

Validation tests that do not meet the test criteria should be addressed to the satisfaction of the competent authority.

(5)     Maintenance

In parallel with this objective/subjective testing process it is envisaged that suitable maintenance arrangements as part of a compliance monitoring programme should be in place. Such arrangements should cover routine maintenance, the provision of satisfactory spares holdings and personnel and may be subject to a regulatory audit.

(f)      Additional features

Any additional features in excess of the minimum design requirements added to an FNPT I, II & III should be subject to evaluation and should be assessed to avoid negative training.