Automatic flight envelope protection for light general aviation aircraft

Abstract

Aircraft loss-of-control accidents account for about 38% of the fatal accidents in U.S. General Aviation operations each year. Loss-of-control accidents include VFR-into-IMC with subsequent disorientation and loss of aircraft control, low-speed stall-spin accidents in the airport traffic pattern, and high-speed accelerated stall accidents during low-level maneuvering. The majority of these accidents could be prevented by full-time flight envelope protection having functionality similar to that available in fly-by-wire systems on newer military and civil transport aircraft. However, fly-by-wire systems would likely be prohibitively expensive to implement in most GA aircraft; and would be impractical for retrofit applications. Under FAA sponsorship, we are developing a new approach to GA Envelope Protection that preserves the existing cable control system, while providing full-time pilot-in-the-loop stability augmentation and flight-envelope protection. This approach, called Force Gradient Control, is made possible by leveraging a new concept in the design of autopilot servos. Under this development effort, we are working to validate feedback control algorithms using a high-fidelity ground-based simulator, in preparation for flight demonstrations using a representative light aircraft. This approach to preventing loss-of-control accidents should be economically viable for both retrofit and forward-fit applications within the General Aviation light-aircraft fleet.