Application of Sequential Quadratic Programming to Rotorcraft Survivability with Power Loss

The DESCENT analysis is a joint effort by the Survivability and Lethality Analysis Directorate and Vehicle Technology Directorate within the Army Research Laboratory. The purpose of the analysis is to assess survivability of rotorcraft with power loss. The program calculates the flight path path of a helicopter after a partial or complete power loss and uses an optimal control procedure to modify this path to minimize impact velocity or to avoid impact and transition to a sustainable flight condition. The flight path is calculated using the sequential quadratic programming algorithm using the commercial optimization package SNOPT. The implementation of the equations of motion and solution of the optimization problem using collocation is described in detail. Results are compared to autorotation test data and examples of the effects of pilot delay and partial power are provided. The optimal control procedure produces flight paths similar to those from the test data.