Real-time assessment and piloted evaluation of fault tolerant flight control designs in the simona research flight simulator

Desktop-based simulations are extremely useful tools for the development of new controller applications and techniques as is evident from the theoretical sections of this book. But, in addition to testing the new controllers in an off-line, desktop-based benchmark simulation, an online piloted moving-base simulator evaluation can give new insights into real-time performance issues, applicability in an operational environment and if applicable, handling qualities of different aircraft configurations. It can serve as a proof-of-concept and allows the assessment of the benefits of the controllers in terms of compensation for impaired aircraft control, performance improvements in failed configurations and lowering of pilot workload. For this purpose, the aircraft model and the fault-tolerant controllers can be implemented in a pilot-in-the-loop flight simulator. Pilots with operational experience on the aircraft in question can be used to assess the efficiency of the controllers and their influence on the handling of the aircraft. Ideally the pilot should not be aware of any differences in handling with the controller engaged for the normal fault free and damaged aircraft, and be able to perform normal flying tasks with satisfactory performance in both cases. To ensure an acceptable level of validity of this assessment, the fidelity of the simulator must be sufficiently high. In addition to the dynamic behaviour of the simulated aircraft model, aspects that influence the fidelity are the appearance and functionality of the flight displays, the feel in the flight controls, the presence and field of view of an outside visual system, and the characteristics of any motion system. To increase reproducibility of the evaluation, these parameters should be documented together with the assessment results. Integration of the controllers in a real-time aircraft simulation environment, which is necessary to perform the piloted evaluation, can help identify implementation issues which would forbid practical introduction in an actual aircraft flight control system. Reliance on physical parameters which are not measured in the aircraft (e.g. sideslip angle), sensitivity to noise and delays in measurements and excessive computational loads are examples of such problems. These issues can usually be evaluated without a pilot actively in control and lead to relatively deterministic results. A more operationally oriented evaluation with a human pilot in the loop introduces variability in the results. To reduce this variation, the experiment design benefits from a well defined test scenario, appropriate performance measures and other human factors related measurement variables. To select the appropriate scenario and measurements, the intended goal of the evaluation has to be taken into account. For a general impression of the flying qualities, a procedure such as an approach and landing can be suitable. If a more detailed insight is required in lateral and/or longitudinal performance or handling qualities, more stylized manoeuvres can be performed. Examples of these include altitude captures, speed and trim changes, bank and heading captures, as well as localizer and glideslope capture and tracking. Apart from the achieved performance, which can be objectively determined, pilot feedback in the form of comments or rating scales for handling qualities (e.g. Cooper-Harper [21]) and Pilot-in-the-Loop Oscillations (PIO) can be valuable subjective results. © 2010 Springer-Verlag Berlin Heidelberg.