Abstract: A method for sensing a takeoff of an aircraft includes receiving a rate of change in vertical motion of the aircraft, determining whether the rate of change in vertical motion of the aircraft exceeds a first threshold, integrating the rate of change in vertical motion of the aircraft and outputting a virtual altitude signal, responsive to receiving the indication that a portion of the aircraft is contacting a surface, delaying the virtual altitude signal through a discrete low pass filter and outputting a delayed virtual altitude signal, subtracting the delayed virtual altitude signal from the virtual altitude signal to output an altitude perturbation signal, determining whether the altitude perturbation signal exceeds a second threshold value, and outputting an indication that the portion of the aircraft is not contacting the surface responsive to the rate of change in the vertical motion of the aircraft and the altitude perturbation signal.

Abstract: A method for sensing a takeoff of an aircraft includes receiving a rate of change in vertical motion of the aircraft, determining whether the rate of change in vertical motion of the aircraft exceeds a first threshold, integrating the rate of change in vertical motion of the aircraft and outputting a virtual altitude signal, responsive to receiving the indication that a portion of the aircraft is contacting a surface, delaying the virtual altitude signal through a discrete low pass filter and outputting a delayed virtual altitude signal, subtracting the delayed virtual altitude signal from the virtual altitude signal to output an altitude perturbation signal, determining whether the altitude perturbation signal exceeds a second threshold value, and outputting an indication that the portion of the aircraft is not contacting the surface responsive to the rate of change in the vertical motion of the aircraft and the altitude perturbation signal.

Abstract: A method for sensing a force applied to an aircraft includes receiving a derivative of the acceleration of a motion of a portion of the aircraft, determining whether the derivative of the acceleration of the motion of the portion of the aircraft exceeds a threshold, and outputting an indication that a force has been applied to the portion of the aircraft responsive to determining that the derivative of the acceleration of motion of the portion of the aircraft exceeds the threshold.

Abstract: A system for sensing a force applied to an aircraft includes a first sensor, a second sensor, and a processor operative to define a first velocity vector as a function of a first velocity due to a rotation motion of the aircraft, define a second velocity vector as a function of a second velocity due to the rotation motion of the aircraft, define an instant axis of rotation of the aircraft as a function of the first velocity vector and the second velocity vector, determine whether a force has been exerted on a first portion of the aircraft, and output an indication that a force has been exerted on the first portion of the aircraft responsive to determining that the force has been exerted on the first portion of the aircraft.

Abstract: A system for sensing a force applied to an aircraft includes a first sensor, a second sensor, and a processor operative to define a first velocity vector as a function of a first velocity due to a rotation motion of the aircraft, define a second velocity vector as a function of a second velocity due to the rotation motion of the aircraft, define an instant axis of rotation of the aircraft as a function of the first velocity vector and the second velocity vector, determine whether a force has been exerted on a first portion of the aircraft, and output an indication that a force has been exerted on the first portion of the aircraft responsive to determining that the force has been exerted on the first portion of the aircraft.

Abstract: A method for sensing a force applied to an aircraft includes receiving a derivative of the acceleration of a motion of a portion of the aircraft, determining whether the derivative of the acceleration of the motion of the portion of the aircraft exceeds a threshold, and outputting an indication that a force has been applied to the portion of the aircraft responsive to determining that the derivative of the acceleration of motion of the portion of the aircraft exceeds the threshold.

Abstract: Primary logic (116-128) for engine failure detection in a multi-engine aircraft is based on thresholds for engine torque (Q), gas generator speed (NG), power turbine inner stage temperature (T5), power turbine speed (NF), throttle setting (PLA), and throttle manipulation (PLADOT).Subroutines for return to dual engine operation (110), backup of the primary logic (200,300) and remaining engine failure (200) are disclosed.

Abstract: The power required for a helicopter to hover is generated (14, 82) as the ratio of current operating power in forward flight (12, 77) determined (10, 73) from data relating operating power in forward flight to power required for hover for the aircraft. The power required to hover is compared (18, 83) with the maximum power available developed (16, FIG. 2; FIG. 3) by an engine model algorithm utilizing actual engine parameters. The comparison of maximum power to power required for hover is utilized to provide an indication (22) to the pilot. The viability of the indication is indicated by a "ready" indication (26).

Abstract: Damping of a helicopter rotor drive train, the drive train including the free turbines of a gas turbine engine propulsion system, the aircraft main and tail rotors, and associated shafts and gears, is accomplished through active modulation of the fuel flow to the engine gas generator. The fuel flow is varied such that a transient torque will be developed by the free turbines which is opposite in phase to drive train resonances.

Abstract: A fuel control (23) for an aircraft engine (10) employs super contingency logic (76) in response to low rotor speed of a helicopter (130) engine failure (131) or entry into an avoid region of a flight regime following engine failure (133) to alter (161, 166-169) limits on the gas generator (30) of a free turbine gas engine (10), whereby following engine failure or in periods of extreme power need, risk of stressing an engine to its failure point is undertaken in favor of acquiring enough power to avoid a certain crash.

Abstract: The blade angle controlling pitch beam servo (26) of a helicopter tail rotor (22) is responsive to a signal manifestation (76) indicative of free turbine engine (20) gas generator speed (78) to provide torque compensation so that the helicopter airframe will not counter-rotate under the main rotor (10) of a helicopter as a consequence of the torque provided thereto by the airframe-mounted engine (20), or in the absence thereof. A trimming embodiment (FIG. 2) provides only sufficient blade angle command (82a) to compensate for that provided by fixed, collective/tail mixing (110-114). Torque compensation tail rotor blade angle commands may be applied through existing stability and autopilot actuators (30-32) or through an additional torque servo (120, FIG. 3).

Abstract: A digital fuel control (53) for a helicopter engine (20) controls fuel flow (52) to the engine in response to a turbine reference speed (62) determined in a normal mode (FIG. 5) to be a rated speed, in a fade-in mode (FIG. 6) to be incremented (117, 120) to an estimated optimum minimum speed (114, 115, 125), in an optimizer mode (FIG. 7) to be incremented (138) in a direction (137) leading to least fuel consumption (135), and in a fade-out mode (FIG. 8) to be incremented (151, 153) back to rated speed (154). The invention provides an engine reference speed which results in minimum fuel consumption during cruise flight.

Abstract: The speed (54, 56) of the free turbine (40) of a helicopter engine (20) is compared (103) with the speed (105, 106) of the helicopter rotor (10) to indicate (101, 102) autorotation, and the deceleration (108) of the rotor above a threshold magnitude (110) is utilized (81, 68, 69) to increase fuel flow (72) to the engine in anticipation of rotor speed droop which would otherwise occur during recovery from the autorotation maneuver.

Abstract: Damping of a helicopter rotor drive train, the drive train including the free turbines of a gas turbine engine propulsion system, the aircraft main and tail rotors, and associated shafts and gears, is accomplished through active modulation of the fuel flow to the engine gas generator. The fuel flow is varied such that a transient torque will be developed by the free turbines which is opposite in phase to drive train resonances.

Abstract: The difference in the speed (54, 56) of a helicopter gas engine (20), free turbine (40) from a reference speed (62, 64) generates (80) a desired acceleration signal (81). The difference (82) in actual turbine acceleration (84, 86) from desired acceleration is integrated (100) to provide an engine fuel command signal (67-73) whenever (88) the speed error signal exceeds (90) a predetermined threshold magnitude.