Patent GB-1023831-A (GB)
Title: Automatic trim correcting system for aircraft
IPC: B64C1/00
Filed: 1962-11-08
Abstract: 1,023,831. Automatic control of aircraft. BOEING CO. Nov. 8, 1962 [Dec. 1, 1961], No. 42241/62. Heading G3R. In a VTOL aircraft control system, attitude correction means is automatically controlled by signals resulting from unintentional variations in attitude, adjusts itself during intentional variations in attitude by the pilot so that it has no effect on the aircraft, and may be arranged to adjust itself so as to be ineffective to control the aircraft despite any variations in attitude of the aircraft. Systems for manually and automatically controlling roll and pitch attitude, heading and altitude of a helicopter are described. In Fig. 1, manual movement of a stick 25 controls, for example, means (not shown) to vary the cyclic pitch and hence roll attitude. With a switch 20 in the "off" position, an electromagnetic brake 23 is energized to lock shaft 24 and thus casing 35 during manual control which, under these conditions, results in an opening of a switch 33A or 33B, according to the sense of control, to prevent operation of a servomotor 42. Automatic control. This is introduced by moving switch 20 to the position shown to deenergize brake 23 and energize a clutch 40 to couple servomotor 42 to cyclic stick 25. Servomotor 42 is controlled, under these conditions, to maintain roll attitude constant by signals applied through an amplifier 63 from a rotor 71 of a synchronous transmission system which includes a pick-off 60 associated with the appropriate axis of a gyro vertical. Adjustment of rotor 71, through reduction gearing, by servomotor 42 provides negative feedback. Temporary change of attitude. This may be made by manually operating cyclic stick 25 during automatic control, the opening of switch 33A or 33B preventing operation of servomotor 42 until the stick is released, whereupon the old attitude is restored. Permanent change of attitude. A new attitude may be set during automatic control by operating a push button 21 and displacing stick manually 25 until the desired attitude it attained. The operation of push button 21 de-energizes clutches 40, 50 so that servomotor 42 is uncoupled from stick 25 and adjusts rotor 71 rapidly to maintain signals there - from at a null in readiness for maintenance of the new attitude when the push button is released. Pitch control. A similar system (not shown) associated with movements of the cyclic stick in a perpendicular direction is described for manually setting and automatically controlling pitch attitude. Heading control. The system for manually and automatically controlling rudder pedals is also similar but different methods for setting a new heading are described. In one method, which is effective when the forward speed exceeds a predetermined value and an airspeed meter renders a silicon rectifier conductive, the aircraft is banked and, when the bank angle exceeds a predetermined value at which a further silicon rectifier is rendered conductive, the synchronous transmission associated with a directional gyro in the heading control system is maintained at a null until the heading is changed to the desired value and bank is removed. In another method, which is effective when the forward speed is below the predetermined value or the helicopter is hovering, the radder pedals are operated and the synchronous transmission from the directional gyro maintained at a null until the new heading is obtained. Altitude control. A push button is operated to close an aneroid chamber at the desired altitude and thereafter A. C. signals from an associated pick-off arranged in a bridge circuit and associated with a transistor amplifier are effective to control an electric motor coupled to a collective pitch controller which may be hydraulic.