Development of a longitudinal flight control system for a new transport aircraft

The control system design presented is part of an effort to create a high-fidelity simulation of a future transport aircraft. A variety of topics is considered, including the dynamics of actuators, the availability of feedback signals, handling qualities requirements, different operational and reversionary modes and their transitions. With regard to aircraft missions like airdrop and low level flight, special emphasis is put on good and responsive flying qualities. In the pitch axis, the normal operational mode is a modified C*-command system. Partial pole placement for a structurally restricted system has been used. Besides the normal operation law, alternative control laws have been implemented for different failure cases. The system is augmented by envelope protections and limitations as well as different compensations like turn or gravity rate compensation. During simulation assessments, interesting results could be obtained on pilot preferences concerning some handling characteristics. For example, it turned out that as soon as a Head-up Display containing a flight-path marker is used for primary control, pilot preferences shifted to a higher bandwidth in flight path angle response, accepting a rather high attitude dropback. Other interesting items concern the consistency and usefulness of some automated envelope limitations when the attitude limits for primary operation are extended.