Abstract: The escape performance evaluation of an ejection seat in China depends mainly on sled tests which may take a long time. Due to the limits of available experimental facilities, research of ejection seat perfor-mance under adverse attitudes is rarely done. In this article, a numerical simulation method is developed to evaluate and analyze the escape performance of ejection seats under adverse attitudes. The ejection progress fell into four phases. The mathematic models of each phase are built. The quaternion method rather than the Euler angular velocity equation is adopted in the free flight phase to resolve the singularity problem of a traditional 6 degree of freedom equation. The mathematic models are solved using four-order Runge-Kutta methods. The computational results agreed well with the sled test experiment data. The ejection seat attitude and trajectory are calculated and analyzed to study the performance of a escape system in adverse attitude conditions. The major causes of poor performance of an escape system under adverse attitude conditions are the instability of the seat at high speed and the influence of aircraft embroiling movement. Some basic methods to improve the escape performance of ejection seats under adverse attitudes are proposed according to the analysis.

Key words: ejection seat, numerical simulation, quaternion method, Runge-Kutta method, adverse attitude