Machmeter

Abstract: Aircraft control apparatus for providing pitch guidance to the pilot during the takeoff acceleration phase between rotation airspeed and steady climbing speed in accordance with Federal Airworthiness Standards for takeoff safety speeds. The steady climbing target speed is determined from computed values of actual coefficient of lift of the aircraft compared to a reference value of coefficient of lift which is programmed in accordance with the number of operating engines, existing thrust to weight ratio, flap position, and leading edge slat extension. The pitch guidance is derived from a control equation which generates a regulating signal for driving the pitch command pointer of an attitude flight director display. Pitch guidance is provided for the pushover acceleration mode during which the aircraft''s takeoff flap-slat configuration is retracted and the aircraft is stabilized on a new climb path at a preset airspeed. Pitch guidance is also provided for a missed approach procedure. Further provision is made for the automatic or manual control of engine throttles to maintain an optimum thrust condition or to maintain a pilot set airspeed, including override means whereby a minimum safe speed based on flap position and computed gross weight will override the selected speed if it is below the computed minimum. An additional override is provided to inhibit pilot selection of airspeeds which are above structural limitations of the flaps. The system requires speed control parameters which are computed by apparatus which provides a measure of the angle of attack and coefficient of lift of an aircraft without external probes or vanes, which measure is derived from computations involving measurements of aircraft longitudinal acceleration, normal acceleration, vertical speed, calibrated airspeed, Mach number, and positions of the movable aerodynamic surfaces which affect the coefficient of lift of an airplane. Supplementary outputs of the computer are signals proportional to acceleration along the flight path, thrust over weight ratio, gross weight of the airplane, potential flight path angle of the airplane, and actual flight path angle.