Patent GB-579819-A (GB)
Title: Improvements in or relating to the control surfaces of aircraft
IPC: B64C23/00
Filed: 1943-06-17
Abstract: 579,819. Fluid-pressure servomotor-control systems. FAIREY. AVIATION CO., Ltd., ORDIDGE, F. H., CHAPLIN, H. E., and COSTIGAN, F. J. June 17, 1943, Nos. 9742 and 14200. [Class 135] [Also in Group XXXIII] Each wing of an aircraft is provided with a full span flap arranged to be depressed, or lowered bodily below the level of the wing, and to be tilted about an axis at or near to the centre of pressure to raise or lower the trailing edge independently of, or concurrently with, the bodily lowering or depressing movement, and is also provided at its upper surface with a member adapted to be projected into the airstream and operable concurrently with the full span flap, the means for controlling the flaps and upper members concurrently being such that in all positions of the full span flaps they may be inclined differentially on the opposite sides of the aircraft for lateral control purposes, while in some positions of the full span flaps the upper members may be employed differentially in relation to one another and each in relation to the full span flap on the other side of the aircraft to assist lateral control, and in other positions of the full span flaps, the upper members may both be projected to serve as air brakes. In addition a second pair of upper members may be arranged to be projected both together when required to act as air brakes. The full span flaps are actuated through servo motors and in some cases also the upper members. The full span flaps may be carried on pairs of links so that they can be lowered bodily or they may be of the tension link, external hinge, or split types, and the upper members may be spoilers or hinged flaps normally nested within or against the main plane, or both may be used as in Fig. 1. Provision is made for a limited degree of lateral control should the servomotors fail. In one form, Fig. 1, two full span flaps 100 are normally nested in recesses beneath the trailing edge of the plane, not shown, and are carried on pairs of links 103, 112, 104, 113 and 105, 114, the links 103, 104 and. 105 being pivoted to the leading edges of the flaps and to the main wing. Two of the rear links 112, 114 are pivoted to links 121, 123 pivoted to the wing about a common axis and the third link 113 is pivoted to a bell crank lever 122, 128 pivoted on the same common axis. Each of the rear links 112, 113, 114 is movable to lower or raise the flap by screwed rods 130 having sprocket wheels 131 turnable through chain and pulley gear from a jack 139 having a pilot valve 152 operable by a bell crank 154 and rod 155 from a flap selector lever 157 movable in the gated quadrant shown. Two spoilers 190 mounted at the mid span of the wing and normally housed in pockets in the upper surface of the wing are connected through bell crank levers to transverse rods 198 connected by links 199 to the ends of a lever 200 pivoted to an arm 170 on the rock shaft 166 of a control lever 167 so that lateral movements of the lever 167 project one or other of the spoilers 190 into the airstream. Simultaneously the arm 170 effects through the linkage shown an axial movement of a spool-like cam 174 engaged by two levers 182 connected to the pilot valves of two independent jacks 151 which actuate through chain gear two screwed rods 134 acting upon the upper ends of the bell crank levers 122, 128 so as to raise or lower the trailing edges of the flaps. Whether the flaps are tilted in opposite directions or whether only one flap is tilted (downwards if nested or upwards if the flaps are fully lowered) depends upon the angular position of the spool which is rotatable by a lever 179 linked to the jack 139 so as to be governed by the depth to which the flaps have been lowered. One end of the lever 200 forms with the arm 170 and links 202, 204 a parallelogram linkage connected by a guided link 205 to one fork 208 of a forked lever 208, 209, the arm 209 having a slot 210 engaging a pin 211 on a block movable along a slide 213 by the throttle control lever 215, the pins 211, 212 being normally in alignment so that the rod 205 cannot move axially. The opposite end of the lever is connected by a rod 216 to a part of the undecarriage so as to be pulled down when the aircraft alights. When the engine is throttled down, the pin 211 is moved along the slot 210 so that as the aircraft touches down the link 205 is raised to tilt the lever 200 and both spoilers 190 are projected to act as air brakes. Opening up the throttle restores the spoilers to their normal position. Two additional hinged flaps 218 normally nested against the upper surface of the wing near the wing roots are connected by arms 231 and links 229 to pins 227 of the links 105, in a slotted offset limb of the link 105. The pins 227 are connected by links 228 to levers 224 which are connected by rods 222, ball crank levers 221 and rods 220 to a two-armed lever 219 on a rotatable sleeve 160 having a bracket 159 to which the lever 157 is pivoted. When the lever is moved through the gate 163 in the quadrant, the pins 227 are moved to the lower ends of the slots 232 on the offset limbs of the levers 105 so that when the flaps 100 are lowered by moving the lever 157 along the slot 162 in the quadrant, the flaps 218 are both projected to act as air brakes during diving. Spring links 156 and 173 in the rods 155 and 172 enable the levers 157 and 167 still to be moved should the jacks jam. Compression springs 186 acting on a lever 185 on the rock shaft 166 are acted upon by a piston 187 subject to pressure from a pitot tube so that the pilot may feel the variation of stiffness of control as the speed varies. As an alternative the rods 130, 134 may be pivoted to the links and bell crank levers at their rear ends and their forward ends are then screwed to engage sprocket wheels acting as nuts. Instead of, or as well as, using upper flaps for braking during diving the spoilers 190 may be caused to be projected simultaneously when the lever 157 is moved through its gate to the 'braking position. For this purpose the lever 200 is divided into two parts 200S and 200P, Fig. 12, their junction being movable along a slot 237 in the arm 170 by a link and lever connection 241, 239 to the sleeve 160 on which the flap selector lever 157 is mounted. Movement of the lever 157 through its gate to the braking position will then raise the junction of the parts 200S, 200P until it is coaxial with the rock shaft 166 and both spoilers will be projected. The outer ends of the parts 200S, 200P are linked to a lever 204, 204S freely pivoted on the shaft 166. In another form, two full span flaps of the tension link type are actuated by jacks directly pivoted to carrier links connecting the wing to points near the leading edges of the flaps. The pilot valves of these jacks are connected through rods 252 to two levers 253, Fig. 14c, mounted on the upper and lower bevel wheels of a differential gear box 269 which is rotatable by a lever 285 connected as shown to the flap selector lever 157 to cause both flaps to be depressed. Lateral movement of the control lever 157 actuates a quick pitch rod 263 to oscillate a lever 265 to raise or lower a ring 268 which engages a crank pin on the forward bevel wheel in the casing so that the levers 253 are moved to actuate the full span flaps differentially. The other connections to the spoilers and flaps are as described in connection with Fig. 1 but the upper flaps may be omitted if the spoilers are projected as described in connection with Fig. 12. The jacks for actuating the full span flaps may act through mechanism involving quick pitch screwed rods similar to the rod 263 instead of directly on the suspension links of the flaps. Fig. 19 shows still another alternative mechanism for actuating the rods 252 for controlling the pilot valves of the flap actuating jacks. The rods 252 are connected to levers 290 rotatable on a vertical shaft 301 and extending through opposite handed helical slots in a sleeve 300 slidable on the rod 301 by connections to the control lever 157. The sleeve is also rotatable by means of splines 302 on the shaft 301 by connection to the rod 155 of the flap selector lever 157. In a further modification the spoilers are omitted, the flaps 218 are placed outboard of the tail planes and are operated differentially by connections to the lever 200 on the arm 170 on the rock shaft 166, Figs. 1 and 14c. Provision is made for varying the amount of projection of the flaps 218 in accordance with the amount of depression of the full span flaps and movement of the lever 157 through its gate to the braking position causes the projection of both upper flaps as described in connection with Fig. 1. In another form involving full span flaps of tension link type and upper outboard flaps 218 both flaps are operated by jacks. The linkage for actuating the upper flaps provides for the fact the a nested flap cannot be depressed by arranging the linkage to pass through a dead centre position in one direction of movement. In this form, Figs. 42c, 42D the rods 198 for actuating the upper flaps are linked one to the lower end of a rocking lever 340 and the other to a pin 344 normally at the upper end of a slot 342 in the rocking lever which is moved by a jack 324 controlled by a link 337, lever 335, and cam 174. This cam is movable axially by connections to the control lever 167 and rotatably by connection to the flap selector lever 157, the main flaps being controlled by the lever 182 acting on the main flap actuating jacks. In this case when the landing wheel brakes are applied the braking pressure fluid causes a jack 348 to collapse a toggle lever 345, 346 to bring the pin 344 to the bottom of the slot 342 and further motion of the jack moves the lever 335 to cause the jack 324 to raise both upper flaps. Movement of the lever 157 through the gate can also pull down the pin 344 after which movement of the lever 157 to braking p