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Helicopter attitude and airspeed acquisition and retention system

  • US 4,382,283 A
  • Filed: 08/08/1980
  • Issued: 05/03/1983
  • Est. Priority Date: 08/08/1980
  • Status: Expired due to Term
First Claim
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1. An airspeed hold autopilot system for a helicopter having a longitudinal cyclic pitch control stick with a trim release switch disposed thereon, comprising:

  • a trim actuator responsive to electrical signals applied thereto to position the longitudinal cyclic pitch control stick of the helicopter;

    airspeed means for providing an airspeed signal indicative of actual helicopter airspeed;

    trim means responsive to said trim release switch for providing a trim release signal;

    position means responsive to said trim actuator for providing a stick trim position signal indicative of the longitudinal cyclic pitch stick trim position established by said trim actuator; and

    signal processing means, responsive to said airspeed signal, said trim release signal, and said stick trim position signal, for providing in response to the presence of said trim release signal, an airspeed reference signal equal to said airspeed signal, and a stick synch signal equal to said stick trim position signal, for providing an airspeed error signal as the difference between said airspeed reference signal and said airspeed signal, for providing in the absence of said trim release signal a pitch autopilot command signal as a function of said airspeed error signal, and for providing a stick reference signal as a function of the difference between said pitch autopilot command signal and said stick synch signal and a stick command error signal applied to said trim actuator as a function of the difference between said stick reference signal and said stick trim position signal, whereby said stick command error signal can be zero during said trim release signal when said pitch autopilot command signal is zero valued and said airspeed reference signal is set equal to said actual airspeed signal so that said airspeed error signal consequently is zero valued, while said stick trim position signal retains a finite value indicative of current stick trim position.

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