SIMULATION-MODEL FOR TAIL ROTOR FAILURE

Tail rotor failure in a helicopter can be a very dangerous and unstabl e condition. For this reason a helicopter simulation model, DYN, has b een formulated to analyze helicopter night response to tail rotor fail ure and steady flight recovery. This model uses classical rotor theory and integrates the nonlinear Euler equations of motion. DYN has been validated against flight tests in several flight regimes in response t o all three main rotor controls. The helicopter used for the validatio n is the McDonnell Douglas AH-64A Apache. The validation also compares dynamic response to FLYRT, the McDonnell Douglas AH-64A flight simula tion model. The results of the validation show fairly good agreement w ith flight test, and even better agreement with FLYRT. Analysis of air craft response following a tail rotor failure shows the potentially ca tastrophic nature of this kind of failure. With the use of some basic feedback control, however, the helicopter may be recovered with some d escent rate and forward airspeed. The relationship between forward air speed and descent rate needed for trimmed flight without a tail rotor is established at the conclusion of this study.