Nonlinear analysis of high angle of attack motions

It is important to understand and predict aircraft departure characteristics throughout the flight envelope. A review of current departure prediction techniques is presented which are based on linearized equations of motion. Included in this review is a unified approach for treating bare airframe and aircraft with augmented stability systems active. The inadequacy of these methods is shown, and the need for nonlinear techniques is presented. Several simple ideas are given which extend the analyses to include nonlinear analysis in departure prediction. However, these methods still lack the requirements for determining the departure characteristics of a truly dynamic system. The application of Liapunov methods to this problem is proposed and a simple example applied to a fighter-type aircraft is given. Another example is presented to which the solution is not known in order to indicate the extent that nonlinearities enter into the departure prediction problem. (Author)