Aircraft pitch-axis stability and command augmentation

Abstract

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).