Improvements in control systems for actuating the control surfaces of an airplane, particularly control systems for conjointly operating the airplane ailerons and landing flaps

摘要

747,507. Controlling aircraft. NORTHROP AIRCRAFT, Inc. Sept. 15, 1953, No. 25450/53. Class 4. [Also in Group XXIX] In a hydraulic servomotor control system controlling the operation of aircraft landing flaps and ailerons having split flaps along their trailing edges, the system is arranged so that the ailerons may be operated separately as ailerons or jointly with the landing flaps to function as further landing flaps, the split trailing flaps being operable when the landing flaps are either fully retracted or fully or nearly fully extended to function as dive-brakes. The combined flap and aileron control unit comprises a control lever 11, Figs. 3, 4, mounted on a bolt 52 which independently mounts outer and inner drive levers 49, 50 and a pulley 51 carrying cables 15, 16. A torsion spring 54 connects the levers 49, 50. In the neutral position of the lever 11, the levers 49, 50 are held apart by a pin 61 secured to the pulley 51. On movement of the lever 11 to its desired position in either direction from neutral, a projecting pin 65 on the lever rotates one or other of the levers 49, 50 to wind the spring 54 more tightly, the spring at its other end acting on the other of the levers 49, 50, to slowly rotate the pulley 51 to operate the cables 15, 16. The cables are connected to the inner groove 17, Fig. 2, of a quadrant 19 having also an outer groove 25 to which are secured follow-up cables 26, 27 connected at their other ends to a nut 32 which cooperates with the screw-threaded end 31 of the drive-shaft 30 of a flap servomotor 42. On rotation of the quadrant about a fixed pivot 24, a link 22 connected to the valve spool of the flap motor control valve 36 moves the spool to supply and exhaust pressure liquid to and from the opposite ends of the servomotor 42 the servomotor operating the flaps through gearing 44 and a shaft 45. At the same time, the shaft 30 and an extension shaft 89 are rotated. The former through the nut 32, cables 26, 27 and quadrant 19 re-centres the valve spool in its neutral position and the latter drives a telescopic shaft assembly 87, Fig. 5, connected through a lever 74 and a variable length screwthreaded unit 79 to the valve spool rod 80 of a control valve 81 controlling the supply and exhaust of pressure liquid to and from the opposite ends of a double-acting aileron servomotor 82 which through a bell-crank 85 and a link moves the aileron 4 downwardly when the flap is extended and returns it to its initial position when the flap is retracted. The ailerons may be operated normally from the cockpit by a pilot's aileron lever which is operatively connected by cables 66, quadrant 67, arm 71 and link 72 to the lever 74 which then moves the unit 79 without affecting its length to operate the aileron control valve 81 to move the cylinder of the servomotor 82 and hence the ailerons, the valve casing moving with the cylinder so that the control valve spool is re-centred in its neutral position. The aileron trailing edge flaps 7, 8 are operatively connected to a servomotor 90, Fig. 6, whose piston and cylinder move simultaneously in opposite directions under the control of a valve 104, having actuating solenoids 105, 106, Fig. 9. The valve 104 is connected by an electric synchronizer 107 to a similar valve 104a on the opposite wing so that the flaps 7, 8 on both ailerons move at the same rate. Movement of a knob 12 in the cockpit controls switches 109, 110 in circuit with the solenoids but the solenoids are not energized until either a switch 114 mounted on the combined landing flap and aileron control unit or a switch 120 mounted on the quadrant 19 closes. The switch 114 closes when the flaps are fully retracted and the switch 120 when the flaps are within 3 degrees of their fully extended position. Anti-creep and shut-off switches are mounted on a shaft operable by the lower trailing edge flap 7, the former closing a circuit when the flaps 7, 8 are within 5 degrees of each other to ensure that they fully close together and the latter opening a circuit when they are 60 degrees apart to prevent any further opening. In another embodiment, the flap cables 15, 16 are connected to a carriage 160, Fig. 10, having a screw-threaded sleeve 161 formed with a square bore which co-operates with a square shaft 159 rotatable through gearing 157 by a screw-threaded shaft 154 connected to the flap motor drive-shaft 30. On movement of one or other of the cables 15, 16, the carriage 160 will be moved together with a nut 162 which engages the sleeve 161 and operates a lever 164 connected to the valve spool of the flap control valve 36a to operate the flap motor 42 and rotate the drive-shaft 30 which rotates the shaft 154 and through the gearing 157 and the sleeve 161 moves the nut 162 to recentre the valve spool in its neutral position. The solenoid-actuated valves 104, 104a and associated electric circuit controlling the motors 90 actuating the split trailing edges of the ailerons are replaced by valves 170, Fig. 11, one for each motor 90, the valves being operable by links 172, 174, 176, quadrants 177 and cables 179, 180 by a pilot's control lever 185. The upper trailing edge flaps 8 are operatively connected by a cable 189 to a follow-up arm 195 which through the links 174, 172 recentres the valve 170 in its neutral position. The cables 179, 180 pass through upper and lower guide tubes 196, Fig. 10, and have fixed thereto stops 204, 205. The tubes 196 carry sleeves 197, 198 which engage the stops and a plate 207 affixed to a nut 206 engageable with the shaft 154 so that on movement of the flap motor 42 the plate 207 is moved. This arrangement replaces the switches 114, 121 of the previous embodiment so that the trailing edge flaps may be moved only when the landing flaps are fully retracted or fully or near fully extended. Adjustable stop-screws secured to the plate 207 at the extreme ends of travel of the plate 207 engage spring-loaded, pivotally-mounted contacts 211 which swing into interference with pawls 217 secured to the shaft 154 to prevent further rotation of the shaft 154. In the event of failure of the pressure liquid supply to the system, contacts on the lever 164 operating the valve 36a engage switches 220, Fig. 13, and on a switch 221 being closed, a motor 224 drives an auxiliary pump 225 to supply pressure liquid to the control valve 36a from a tank 235. A solenoid-actuated valve 234 normally permits exhaust liquid from the valve 36a to the main supply tank but on the closing of the switch 221 flow is diverted to the tank 235. A check valve 232a prevents return flow from the pump 225 to the main supply line 39.