United Technologies Corporation

Lou S Cotton

Don L Adams

David J Verzella

Richard D Murphy

Franklin A Tefft

Raymond G Johnson, Jr

The longitudinal cyclic pitch channel of a helicopter has a negative pitch rate feedback bias added thereto when flying at higher speeds, thereby to stabilize the pitch axis against aft-load maneuvering instability and/or to induce a requirement for the pilot to provide a countermanding longitudinal cyclic pitch input through his cyclic pitch stick, the normal feed force of which provides an indication to him of the loading of the rotor as a consequence of undergoing pitch rate maneuvers.

Helicopter pitch rate feedback bias for pitch axis maneuvering stability

The factors (including collective pitch, weight, altitude density, rotor speed and airspeed) which determine the extent to which the rotor of a helicopter may be loaded, are fed into a look-up table, and the permissible acceleration normal to the rotor is compared against actual acceleration normal to the rotor, an alarm signal resulting whenever the actual exceeds the permissive; the alarm signal may be utilized to shake the collective stick so as to simulate pre-overload vibration as a warning to the pilot.

Aerodynamic surface load sensing

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 actuators acting in series, controlled in a closed-loop fashion by electronic hardware, 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. A test switch introduces an imbalance to test the fault circuitry. The stabilator is biased to assume a maximum incidence position 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. 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 a canted tail rotor which 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 washed-out at low speeds. The bias allows final adjustment for high speed flight.

Variable incidence helicopter stabilator and fail safe actuator

In a helicopter having an automatic pilot system for controlling the main rotor collective pitch, main rotor longitudinal and lateral cyclic pitch, and tail rotor collective pitch, in response to inputs provided from normal sensors, navigational instruments and controls, (which include among others as is known, doppler radar, a pilot panel, an air speed indicator, a radar altimeter, a barometric altimeter and a longitudinal accelerometer), commands to control automatic approach to a desired hover position are provided to the autopilot system in response to signals normally supplied by a TACNAV unit as well as the sensors, navigational units and controls; controls are provided for altitude and rate of descent, so as to terminate in hover at a desired altitude, as well as for turns, courses, and speed so as to approach the desired point of hover upwind and to decelerate in a controlled fashion to hover.

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Monroe, CT, United States of America

Lou S Cotton