GB895851A - Flight control mechanisms for aircraft - Google Patents

Abstract

895,851. Controlling aircraft. VICKERS AIRCRAFT HOLDINGS Ltd. Jan. 21. 1959 [Feb. 4, 1958], No. 3626/58. Class 4. Aircraft control apparatus comprises a flight control member, a flight control organ e.g. an elevator, means for representing the force applied to the control member as a hydraulic pressure, a device for producing an output representing the difference between said pressure and a force proportional to the acceleration of the aircraft at a predetermined point thereof, and a servomechanism applying a force to the control member under the control of said device. The acceleration is a linear acceleration through the aircraft longitudinal axis and normal to the lateral axis, or acceleration due to pitching or rolling motion if the predetermined point is not at the aircraft centre of gravity. In the embodiment described, a pilot's control column 10 is pivoted at 12 to a link 11 connected to the elevators, and is pivoted at 101 to the rod 13 of a piston 14 in a cylinder 15 acting as a forcepressure transducer. The two ends of the cylinder are connected by conduits 16, 17, to two chambers 18, 19 separated by a spring balanced normal acceleration responsive mass 20 connected by links 21, 22 to the valve 23 controlling the connection of fluid pressure and return conduits 231, 232 to the chambers of a jack 25. The rod 26 of the piston 24 of the jack is pivoted at 27 to a lever 28 pivoted to the airframe at one end 281 and supporting cylinder 15 at its other end. Also connected to rod 13 is the output link 29 of an artificial feel unit adapted to urge the control column 10 to a datum position by a force increasing with the displacement of control column 10 and variable with airspeed. Normal acceleration of the aircraft displaces mass 20, which admits fluid under pressue to one side of piston 24, and thus sets up a force on the control column 10. If resisted by the pilot, this force increases until the pressure differential produced in transducer 14, 15, and transmitted to chambers 18, 19, is sufficient to recentre mass 20 and valve 23. Thus the control column force required per g of normal acceleration is constant. This relationship is, however, modified by the centering force applied by the artificial feel unit through link 29. If the pilot flies " hands off," displacement of mass 20 and operation of the servomotor displaces the control column, until the force applied by link 29 to the transducer 14, 15 recentres mass 20, so that the elevators are operated in the sense to reduce the normal acceleration. To counteract time lags in operation of the system, the linkage 21, 22 may be such as to produce an output displacement dependent on the input displacement and its rate of change, or the mass 20 may be located well ahead of the centre of gravity of the aircraft.