Instrumentenlandeeinrichtung fuer Luftfahrzeuge

1,131,731. Automatic control of aircraft. LEAR SIEGLER, Inc. June 3, 1966 [June 14, 1965], No.24760/66. Heading G3R. In an automatic landing system for an aircraft, a roll control surface is controlled by electrical signals, dependent on roll attitude, applied both directly and through a low-pass filter, combined with electrical signals, dependent on displacement from a glide path, applied both directly and through a rate circuit. As shown, D.C. signals from a radio receiver, in response to angular displacement of an aircraft from the centre-line of a localizer radio beam, are applied at 24 so that through a modulator 4, line 34, limiter 8 and servo-amplifier 10 they control ailerons 20 to restore the aircraft to the beam centre-line. A differential component of these signals is derived by a high-pass filter 5 and added through a low-pass filter 6. Gyroscopically derived stabilizing signals dependent on roll and rate of roll are also applied to the aileron control system at 23 and 22 respectively. Stability is further improved by applying the roll signals through a low-pass filter 3 to the input of limiter 8. A steering bar type indicator 40 is provided to permit manual steering of the aircraft to the beam centre-line. Gyroscopically derived signals dependent on yaw rate are applied at 25 and, through a low-pass filter 15 and servo-amplifier 16, control rudder 21. Just prior to touchdown, an altimeter 19 closes a switch 12 so that signals dependent on error in the heading relative to that of the runway, applied at 26, are rendered effective to control the rudder if they exceed a magnitude determined by a dead zone 13. The aircraft is thus aligned with the runway and, upon touchdown, strutoperated switches 18, 14 short out the dead zone device and introduce the localizer signals so that the latter control the rudder during the run after landing.