The Boeing Company

Richard S Breuhaus

Kioumars Najmabadi

Robert J Bleeg

Monte R Evans

Edward E Coleman

Timothy A Nelson

Dorr Marshall Anderson

A bias correction system for use in a neutrally-stable aircraft having a control column and a pitch control system is provided. The position of the control column is generally represented by a control column position signal. The bias correction system is for removing control column bias when the control column is in a neutral position. The bias correction system includes a first combining unit for combining the control column position signal and a correction signal, and a switch. The switch includes activated and deactivated states. The switch is set to the deactivated state when the control column is physically displaced from its neutral position. The deactivated state allows the correction signal to remain at its last value, the activated state allows the correction signal to equal approximately the control column position signal. In one embodiment, the bias correction system includes a smoothing filter for receiving the control column position signal and outputting a smoothed correction signal when the switch is in the activated state. In another embodiment, the bias correction system includes a unit for limiting the correction signal to control column position signal values within a limited predefined range.

Aircraft pitch-axis stability and command augmentation system

A method of providing speed protection to a neutrally-stable aircraft including the calculation of at least one of a stall protection signal and an overspeed protection signal. The aircraft includes a pitch control system having a command pitch signal received from pilot input to a control column. The protection signal is provided to the pitch control system to limit the commanded pitch signal during flight. The calculation of a stall protection signal includes differencing the aircraft's current airspeed with a reference speed and multiplying the difference by a scaling factor that corresponds to the force required by the pilot to move the control column. The calculation of an overspeed protection signal includes calculating a first signal based on airspeed, calculating a second signal based on Mach, selecting the large of the two signal and passing it through a limiter. The limiter is a function of roll attitude and corresponds to the force required by the pilot to move the control column. Also provided is a method of calculating a flare compensation signal to emulate ground effects encountered by an aircraft while executing a landing. The flare compensation signal is determined using a table of gear heights versus flare compensation amounts. The flare compensation signal is limited to a value between zero and a positive upper limit.

Method of speed protection and flare compensation for use with aircraft

Disclosed is a pitch-axis stability and command augmentation system (19) in which a pilot column input (.delta..sub.C) is provided to a pitch command processor (26), the output of which is a C*U feedforward command (C*U.sub.FFC) that is supplied as an additive input to a combining unit (20). The combining unit (20) receives a second additive input of an augmented feedback command signal (AFB.sub.COM). The resulting output is filtered and generates an elevator command signal (.delta..sub.e,FILT). The command processor (26) additionally supplies a corrected column position signal (.delta..sub.C,COR) to a pitch command C*U processor (26) that converts the corrected column position signal (.delta..sub.C,COR) into a C*U pitch command (C*U.sub.PilotCmd), representative of the pilot's requested elevator pitch which is generated by movement of the control column. A computed C*U processor (32) forms a computed C*U signal (C*U.sub.Computed) that is based on the current state of the aircraft. The C*U processor (32) includes a speed stability processor (150) that computes the difference between a reference speed (V.sub.REF) and calibrated airspeed (V.sub.CAS). The speed stability processor (150) includes phugoid damping (400) in generating a speed error signal (E.sub.z), and providing a means by which the pilot may set a reference airspeed (V.sub.REF) by using a trim device. An underspeed protection signal (C*U.sub.US) is supplied by a stall protection processor (416). A flare compensation signal (C*U.sub.FR) is supplied by a flare compensation processor (414). An overspeed protection processor (412) supplies an overspeed protection signal (C*U.sub.OS). A combining unit (424) is provided to combine the stall protection signal (C*U.sub.US), flare compensation signal (C*U.sub.FR), and overspeed protection signal (C*U.sub.OS) to form a compensation and protection signal (C*U.sub.C&P). A combining unit (22) combines the pilot-requested C*U command (C*U.sub.PilotCmd), the computed C*U signal (C*U.sub.Computed), and the compensation and protection signal (C*U.sub.C&P). The resulting signal is an error signal (E.sub.C*U) which is supplied to an integrator (28) that outputs a C*U integral command signal (IC*U.sub.COM). Another combining unit (23) receives the C*U integral command signal (IC*U.sub.COM) and combines it with a pitch rate damping command signal (Q.sub.COM). The output of the combining unit (23) is the augmented feedback command signal (AFB.sub.COM).

Disclosed is a pitch-axis stability and command augmentation system (19) in which a pilot column input (.delta..sub.C) is provided to a pitch command processor (26), the output of which is a C*U feedforward command (C*U.sub.FFC) that is supplied as an additive input to a combining unit (20). The combining unit (20) receives a second additive input of an augmented feedback command signal (AFB.sub.COM). The resulting output is filtered and generates an elevator command signal (.delta..sub.e,FILT). The command processor (26) additionally supplies a corrected column position signal (.delta..sub.C,COR) to a pitch command C*U processor (26) that converts the corrected column position signal (.delta..sub.C,COR) into a C*U pitch command (C*U.sub.PilotCmd), representative of the pilot's requested elevator pitch which is generated by movement of the control cola. A computed C*U processor (32) forms a computed C*U signal (C*U.sub.Computed) that is based on the current state of the aircraft. The C*U processor (32) includes a speed stability processor (150) that computes the difference between a reference speed (V.sub.REF) and calibrated airspeed (V.sub.CAS). The speed stability processor (150) includes phugoid damping (400) in generating a speed error signal (E.sub.z), and providing a means by which the pilot may set a reference airspeed (V.sub.REF) by using a trim device. An underspeed protection signal (C*U.sub.Us) is supplied by a stall protection processor (416). A flare compensation signal (C*U.sub.FR) is supplied by a flare compensation processor (414). An overspeed protection processor (412) supplies an overspeed protection signal (C*U.sub.OS). A combining unit (424) is provided to combine the stall protection signal (C*U.sub.Us), flare compensation signal (C*U.sub.FR), and overspeed protection signal (C*U.sub.OS) to form a compensation and protection signal (C*U.sub.C&P). A combining unit (22) combines the pilot-requested C*U command (C*U.sub.PilotCmd), the computed C*U signal (C*U.sub.Computed), and the compensation and protection signal (C*U.sub.C&P). The resulting signal is an error signal (E.sub.C*U) which is supplied to an integrator (28) that outputs a C*U integral command signal (IC*U.sub.COM). Another combining unit (23) receives the C*U integral command signal (IC*U.sub.COM) and combines it with a pitch rate damping command signal (Q.sub.COM). The output of the combining unit (23) is the augmented feedback command signal (AFB.sub.COM).

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Issaquah, WA, United States of America

Richard S Breuhaus