Selbsttaetige Steigungssteuerungsanlage fuer Flugzeuge,insbesondere landende Flugzeuge

997,707. Automatic control of aircraft. LEAR SIEGLER Inc. Aug. 14,1962 [Oct. 30,1961], No. 31083/62. Heading G3R. [Also in Division B7] In a system for automatically controlling the pitch of an aircraft during landing, electrical signals dependent on the rate of descent, pitch altitude and pitch rate are combined to oppose a signal dependent on vertical deviation from a radio beam and a further signal which is progressively modified after a predetermined altitude is reached. In Fig.1, prior to an aircraft commencing a radio glide path descent, a potentiometer unit 16 is manually set to produce a signal which is applied through a potentiometer 24, set at maximum, and a summation unit 35, to the pitch channel of an autopilot (not shown) to give an angle of descent equal to that of the glide path. Thereafter, vertical deviations from the centre of the glide path are detected by a radio receiver 10, signals from which are applied through a potentiometer 12, also at maximum, to control a servomotor 15 adjusting potentiometer 16 to restore the aircraft to the glide path. Rate feedback is provided by a tachometer generator 18 associated with motor 15 and feedback from potentiometer 16 is provided through a wash out filter unit 21. Damping is provided by the addition of signals from a rate of pitch gyro 40, signals from a pitch altitude detector 36 applied through a further wash-out filter 37, and signals from a barometric rate of descent detector 28 which are combined with signals from a vertical accelerometer 30 in such proportion as to compensate for phase shift due to a lag network 32. When the aircraft has descended to a predetermined altitude, e.g. 200 ft, a radar altimeter 27 commences to operate potentiometer 12 so that, during descent to a lower predetermined altitude, e.g. 50 ft, the signals from the glide-slope receiver 10 are progressively reduced to zero since they become unreliable. During the remainder of the descent, altimeter 27 progressively decreases potentiometer 24 to a 20% setting so that the descent is flattened out for landing. In a modification, amplication and Zener diode limiting is applied to the signals from the glide path receiver which are applied through potentiometer 12 directly to the autopilot instead of controlling potentiometer 16. Above 200 ft potentiometer 16 is controlled by signals from rate of descent detector 28 in readiness for switching into the control system at that altitude by altimeter 27.