Abstract: The gain of a stability augmentation system for an aircraft, particularly a helicopter, is automatically varied in accordance with the gross weight and deviations of the center of gravity of the aircraft. Gross weight and center of gravity are identified from in-flight measurements of collective and cyclic pitch stick position and airspeed. The gain of the stability augmentation system will not be changed during periods when the aircraft is being maneuvered.

Abstract: 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.

Abstract: To prevent inadvertent ground contact of the tail of a helicopter during a landing operation without providing a continuous warning signal for normal landings the altitude and attitude signals are scaled such that when they are equal and opposite in voltage and phase compared to a ground contact curve the comparator will energize a relay for actuating a pilot warning signal. A rate of descent signal biases the altitude signal upward varying in proportion to rate of descent as to enable the pilot to have sufficient warning time to take corrective action.

Abstract: Apparatus for measurement of the velocity of a helicopter with reference to the air comprises two measurement systems that are substantially identical, associated with a double indicator. The measurements are effected with reference to the longitudinal axis and the transverse axis of the helicopter. Each measurement system comprises a position detector for detecting the position of the cyclic rotor pitch command member along one axis, and a detector of the acceleration component along the same axis, with a substantially identical measurement system associated with the other axis. Computing means effect integration of the algebraic sum of the measured values, and pass signals to the double indicator which indicates velocity of the helicopter along the axes. The acceleration detectors include pendular levels, and all detectors incorporate measurement potentiometers. The apparatus is especially useful in the measurement of the air speed of a helicopter close to hovering conditions.

Abstract: To prevent inadvertent ground contact of the tail of a helicopter during a landing operation without providing a continuous warning signal for normal landings the altitude and attitude signals are scaled such that when they are equal and opposite in voltage and phase compared to a ground contact curve the comparator will energize a relay for actuating a pilot warning signal. A rate of descent signal biases the altitude signal upward varying in proportion to rate of descent as to enable the pilot to have sufficient warning time to take corrective action.

Abstract: An indicator for a flight director instrument particularly for use in rotary wing aircraft includes a command cue having a shape resembling that of an associated aircraft control element or stick and includes cooperating indicia representative of the direction to move the control stick so as to center the cue and thereby satisfy the command. This novel indicator arrangement engenders an instinctive pilot response to move the associated control stick to satisfy the flight director command.