DESCENT Analysis for Rotorcraft Survivability with Power Loss

An analysis has been developed to model a rotorcraft with power loss. Partial power recovery to a flyaway condition, partial power landing, and autorotation to landing with a complete power loss are considered. An optimal control procedure is implemented to predict the pilot response to the power loss with the objective of minimizing the horizontal and vertical impact velocities in the case of a landing and achieving a sustainable steady state flight condition for flyaway. The physical and optimal control models are based on previous work, but have been extended with rate controls and additional constraints to more closely represent the pilot reaction and physics of the helicopter motion. The model is validated for autorotative landings from hover and forward flight initial conditions with data from a high energy rotor system flight test. With appropriate inputs to simulate the flight paths in the test data, good agreement is observed between the optimal control solutions and the test data. An example flyaway case is presented to illustrate the strengths and weaknesses of the current implementation.