Nonlinear Analysis of Aircraft Loss-of-Control

Loss-of-Control (LOC) is a major factor in fatal aircraft accidents. Although de nitions of LOC remain vague in analytical terms, it is generally associated with ight outside of the normal ight envelope, with nonlinear in uences, and with a signi cantly diminished capability of the pilot to control the aircraft. Primary sources of nonlinearity are the intrinsic nonlinear dynamics of the aircraft and the state and control constraints within which the aircraft must operate. This paper examines how these nonlinearities a ect the ability to control the aircraft and how they may contribute to loss-of-control. Speci cally, the ability to regulate an aircraft around stall points is considered, as is the question of how damage to control e ectors impacts the capability to remain within an acceptable envelope and to maneuver within it. It is shown that even when a su cient set of steady motions exist, the ability to regulate around them or transition between them can be di cult and nonintuitive, particularly for impaired aircraft. Examples are provided using NASA's Generic Transport Model.