Patent GB-709510-A (GB)
Title: Improvements in or relating to an airplane control system
Inventor: FEENEY THOMAS AQUINAS
IPC: B64C13/00
Filed: 1952-11-11
Abstract: 709,510. Controlling aircraft. NORTHROP AIRCRAFT, Inc. Nov. 11, 1952, No 28369/52. Class 4 An aeroplane trim control system is connected between the pilot's control element and the framework of the aeroplane, and comprises elastic control centering means and a linkage of adjustable length, and pilot operated means for resetting the length of said linkage to provide a new neutral control position. The control system to which the invention is applied is shown in Fig. 1, in which the two cable quadrants 22 and 23 each control an elevon, by rotating axle 32 to move the valve rods 36 of two floating servomotors 35 which follow up their valve rods moving levers 43 and the elevon through rods 45. The other elevon is similarly operated. The joystick assembly, also shown in Fig. 2, includes a stick 19 attached to a cross head 12 mounted to rotate about two perpendicular axes. The cross head has two bevel gears 16 and 17 fastened to it, each meshing with a bevel gear quadrant 5 and 4, driving cable quadrants 23 and 22 via concentric shafts 2 and 1. Rotation of the stick about the axis of shafts 1 and 2 will rotate the bevel quadrants 4 and 5 without relative displacement, which operates the elevons differentially for roll control. Rotation of the stick about the axis of the cross head rotates the bevel gear quadrants in opposite senses producing similar movement of the elevons for pitch control. Centering means are shown in Fig. 2, in which 51 is the extensible linkage, joined by rod 52 to bell crank lever 54, attached to the framework through the double acting spring case 62. This, shown in Fig. 7, consists of a housing 62 containing two slides 78 and 79 urged apart by spring 81. Rod 77 moves in the sliders 78 and 79; and has abutments 80 and 61 adapted to contact the outside of the sliders thus producing a centralizing force. Instead of, or as well as, the spring centralizing means, an airspeed operated device 67 may be used, in which a diaphragm 68 is subjected to a permanent bias from spring 72 and to static pressure in chamber 71 and dynamic head pressure in chamber 70. The resultant force is passed to the pilot's control element by a cam follower 66 on lever 64 in contact with cam 57, connected to the lever 54. The extensible linkage is shown in Fig. 6, where rods 49 and 52 are connected into the trim control system. A hydraulic path is provided between the ends of cylinder 51, which path is normally closed by valve 102. locking the piston 85 in the cylinder. If the aircraft becomes out of trim, the pilot opens valve 102 by means of switch button 21 (Fig. 2) on the joystick, and the centering means, instead of acting on the joystick will move piston 85 to a new position in cylinder 51, effecting trim. Emergency manual operation of valve 102 is provided by cable 111, should the electrical operation fail. Constrictions 110 and 109 are provided in the hydraulic circuit, and all except 109 can be by-passed by valve 106, operated by the landing gear for rapid trim at takeoff and landing. The extensible linkage may be connected between the centralizing means and the aircraft framework.