GB778458A - Altitude control system - Google Patents

Abstract

778,458. Automatic control systems for aircraft. BENDIX AVIATION CORPORATION. Nov. 9, 1954 [Nov. 13, 1953], No. 32426/54. Class 38 (4). To maintain a two-engined aircraft automatically at a chosen altitude, an altituderesponsive bellows is clutched to an inductive type pick-off at that altitude to produce in a stage 14, Fig. 1, A.C. altitude error signals which are applied through a thermionic valve circuit 16 and an amplifier 40 to operate a two-phase reversible servomotor 42 adjusting a propeller speed controller 43 correcting altitude. Propeller speed controller 43 may alternatively be operated manually. Circuit 16 provides signal limiting with operation of an alarm if the altitude error signal exceeds a predetermined value and includes thermally controlled bridge circuits which introduce components dependent on the rate of change of error and the integral of the error. Displacement and rate feedback is provided through stages 46 and 44. The signal from stage 46 is also applied through amplifiers 50, 51 to control servomotors 52, 53 adjusting the aircraft engine throttles, signals dependent on the engine manifold pressures, developed in stages 60, 61, also controlling the engine throttles to ensure a predetermined relationship between the setting of propeller speed controller 43 and engine manifold pressure. This relationship is made non-linear by a stage 58 which is introduced to apply a further signal to the throttle servo systems when the movement of the propeller speed controller 43 exceeds a predetermined upper speed setting. The outputs of amplifiers 50, 51 are maintained at a null when automatic control is not in use by feedback which is then effective through stages 62, 63. An altitude error signal from stage 16 is also combined with a signal from the pitch pick-off of a gyro vertical 28 to control, through a combined thermionic and magnetic amplifier 18, a two-phase reversible servomotor operating the aircraft elevators 22 which thus assist in the attainment of the desired altitude. Displacement and rate feedback is provided through stages 26 and 24. If one engine fails, manual operation of a feathering switch causes a bias voltage to be applied to the input of amplifier 40 to increase the thrust of the other engine. Specifications 603,610, [Group XXXVI], 662,831, 662,833, 662,853, 670,568, 679,560 and 693,085, [Group XL (c)], are referred to.