Patent GB-849307-A (GB)
Title: Improvements in manoeuver limiter for aircraft
IPC: B64C13/24
Filed: 1957-08-29
Abstract: 849,307. Controlling aircraft. GENERAL ELECTRIC CO. Aug. 29, 1957 [Aug. 31, 1956], No. 27227/57. Class 4. [Also in Group XXXV] An aircraft control system having a control stick, command signal generating means associated with the control stick, and a servo operated by the command signal to activate an aircraft control surface, is characterised in that the generated command signal is proportional to force applied to the control stick only in a limited and predetermined range of applied force and limited movement of the control stick, and the servo and control stick are operatively linked so that upon application of force substantially greater than said limited force the control stick and the servo and its associated aircraft control surface are moved beyond said limited movement. A control column 10 pivoted at 44 on the aircraft, has a rigid internal connection 13 for a flexible control stick 12 which may be manually deflected in the column between the limiting positions 15a, 15b. The stick carries a contact 18 which wipes over a potentiometer 14, energised by a voltage source 16, to derive a signal of magnitude and polarity determined by the position of the stick. This signal is combined with a fixed voltage tapped at 26 from a voltage generator 28 according to the pitching characteristics of the particular aircraft, the combined signal being fed to the rotor 22 of a selsyn 24, the output from the stator 30 being amplified at 32 to operate a motor 34 to rotate the elevators 36. A feedback signal is fed to the amplifier by follow-up 38 and motor 34 drives a tachometer 42 which supplies an anti-hunting signal stator 30. Column 10 is connected by linkage 45 and gearing 48, 49 to motor 34 so that rotation of motor 34 operates through gearing 49, 48 and link 45 to move the column 10 in the same sense as movement of stick 12. When stick 12 reaches either of its limit positions within the column, further movement operates the column about pivot 44 and, through connection 45, 48, 49, the motor 34. This would result in the generation at 38 of a further feed-back signal tending to restore the motor to its original position and provide the pilot with a 'feel' resistance supplementary to that provided by the deflection of stick 12. To ensure that the aircraft is not subjected to excessive loading as the result of full elevator movement under adverse conditions e.g. when pulling out of a dive, an accelerometer 50 generates a signal which is amplified at 52 to rotate a motor 54 connected to the rotor 22 of selsyn 24 whereby the input signal to amplifier 32 may be reduced automatically to prevent excessive elevator movement. When the aircraft is controlled automatically, e.g. by a rate gyro 60, the signal developed by the gyro is passed through a diode limiter 62 consisting of rectifiers 64, 66 respectively biassed by resistors 68, 70 (energised from source 16) so that the developed signal cannot exceed a predetermined maximum. To prevent such signal being fed to the control channel when under manual control, the control column is provided with an automatic switch 72. This comprises a contact 75 on stick 12 which upon movement of the stick engages either of spring mounted contacts 76 or 77 to energise a solenoid 78 to open contacts 73 and close contacts 74. With the control column in mid-position switch 72 would be de-energised with the circuit from gyro 60 to selsyn 24 completed through contacts 73. The invention may be applied to operation of control surfaces other than elevators and manual operation may be replaced by hydraulic or electrical control.