An Analysis of the Stability of an Aircraft Equipped with an Air Cushion Recovery System.

摘要

The stability of an aircraft equipped with an air cushion recovery system (ACRS) was investigated both in-flight and during the landing (slideout) phase of flight. Digital computer simulations were used to identify unstable tendencies of a specific aircraft (the Jindivik drone). Control system designs are proposed to eliminate the instabilities. A nonlinear, six degree of freedom, aerodynamic model is developed based on available wind-tunnel data. The model is used in a computer software package, EASY, to simulate the vehicle in flight. A model of the air cushion recovery system is also developed. The model is generated by matching experimental data obtained from an actual ACRS with 14 spring/damper units. the model is verified by computer simulation, and the slideout simulations are performed. These simulations reveal a lateral-directional instability in the slideout. An optimal control design is proposed and verified, after which it is shown that the stability of the system is dramatically exhanced by the addition of an optimal controller.