GB743541A - Improvements in or relating to airplane trim control - Google Patents

Abstract

743,541. Controlling aircraft. NORTHROP AIRCRAFT, Inc. April 21, 1953, No. 10910/53. Class 4. In an aircraft provided with power-operated control surfaces and elastic means to provide the pilot with a sense of " feel " when operating a control member, powered means are incorporated whereby the neutral position of the control member may be adjusted to compensate for out-of-trim positions of the surfaces. The invention may be applied to the control systems of any of the movable control surfaces and in the embodiment shown it is incorporated in the mechanism for the rudder. The rudder bar pillar 1, pivotally mounted in a fixed plate 3, carries an arm 4 which is coupled to, and normally is held in neutral position by, the central movable rod 5 of a double-acting spring box 14. The other end of the box 14 is pivoted to one end of an arm 17 mounted on a fixed pivot 18 and connected at its other end to a screw-operated extensible link 20, 21 which is operated by a reversible electric motor 22 through a gear-box 23, the gear-box being anchored to the plate 3. Limit switches 25, 26, actuated by movement of the end caps of the spring box 14, and a master switch in the handle of the control column (not shown) are connected in a circuit with the motor 22 and a power source (not shown). Movement, by the pilot, of the rudder bar to trim the aircraft will cause relative movement of the elements of the spring box 14 to close one or the other of the switches 25, 26, and to restore the rudder bar to its neutral position with the rudder in a trimmed attitude, the pilot closes the switch in the control column to complete the power circuit to the motor 22 which will be energized to lengthen or shorten the link 20, 21.