| 摘要 |
<p>VARIABLE INCIDENCE HELICOPTER STABILATOR AND FAIL SAFE ACTUATOR A helicopter stabilator, combining the functions of tail stabilizer and aircraft elevator, has its angle of incidence with respect to the helicopter controlled by means of a pair of reversible electric jack-screw type actuators acting in series, each being controlled in a closed-loop fashion by separate electronic hardware, the position of each as well as the rate of change thereof being compared with the other, the controls being disconnected when the actuators fail to track within a threshold disparity of either position or rate of change of position of each other, whereby catastrophic aerodynamic changes, which could otherwise occur from electronic or actuator failure, are avoided, but dynamic loads do not cause unnecessary failure indications. A test switch introduces an imbalance to test the fault circuitry. The stabilator is biased to assume a maximum incidence position so as to be insensitive to the substantially vertical component of main rotor downwash, at low speeds, including hover; and inputs from airspeed and collective pitch position cause it to assume a substantially level position at higher, cruise speeds, for maximum forward flight stability. A pitch rate gyro input controls the stabilator for stable flight against pitch-inducing flight commands and external effects, such as gusts. In one embodiment, the electronic controls are related to a canted tail rotor which not only provides directional stability, but also provides tail lift; to overcome tail-up and tail-down effects of the downward component of the tail rotor due to more or less thrust and real or apparent lateral accelerations, a lateral accelerometer is used. To avoid main rotor downwash against the stabilator at hover, the lateral accelerometer and collective pitch inputs are washedout at low speeds. The bias allows final adjustment for high speed flight. The invention disclosed herein was made under or in the course of a contract with the Department of the Army.</p> |
