Patent GB-313419-A (GB)
Title: Improvements in or relating to aircraft
IPC: B64C23/00
Filed: 1928-02-02
Abstract: 313,419. Thurston, A. P. Feb. 2, 1928. Steering and balancing.-Aircraft having movable alulas mounted upon the leading edges of the wing are provided with an air directional control device such as a wind vane which acts automatically to prevent functioning of the alulas when the attitude or speed of the machine is such that there is no danger of stalling. The device may act to prevent the movement of automatically moving alulas, or where there is an interconnection, between the alulas and the aileron control it may disconnect the alulas from the aileron control and lock them in their inoperative position. The alulas may be such as are described in Specifications 180,359 and 310,988. Fig. 3 shows a control device wherein the aileron and alula control cables are connected respectively to two levers 17, 15 of which the lever 17 is rigidly mounted a rocking shaft 16 and the lever 15 is rotatably mounted thereon. The two levers are interconnected by a spring 18 so that they can be moved simultaneously by movement of the control lever 4. During normal flight, however, the lever 15 is locked in its mid position to keep the alulas inoperative by a catch 19 which is connected through the linkage shown to a forwardly projecting pivoted wind vane 23. Should the machine approach the stalling angle the vane 23 moves upwards suddenly to trip the catch 19. The vane 23 may be loaded to cause the alulas to be thrown into operation at less inclination of the machine when flying slowly than when flying fast. In an alternative the lever 15 is normally centred by a spring and the vane 23 arts to couple or uncouple a clog-clutch connection to the shaft 16. Fig. 6 shows a pneumatic relay device wherein the alula control is normally held inoperative by connections to a rod 42 secured to a piston 40 in a cylinder 38 connected through a pipe 39 to the engine induction pipe which maintains a partial vacuum in the cylinder. When a valve 44 is opened by movement of the vane 23 the vacuum is destroyed and spring 41 moves the rod 42. A valve 45 in the pipe 39 prevents the vacuum from being destroyed by momentary failure of suction in the pipe 39. The rod 42 may operate the alulas directly. This device may be used also for normally preventing the opening of slots formed by automatically moving alulas, the rod 42 for this purpose being connected to a pulley acting on the bight of a cable connected to the alulas on the two sides of the machine. Alternatively the vane mav act upon the lever 48 of a rotary valve 45, Fig. 11, of a piston and cylinder servo motor to put the cylinder into communication through ports 51, 50 with a suction pipe 39 or to a port leading to an air passage 53. Fig. 7 shows a double-acting cylinder in which two pistons 40 are connected by a rod 42 acting on a lever 47 connected to the alula control cables. The ends of the cylinder are connected through passages 46 to a distributing valve 45 moved by the aileron control through a lost motion connection, the wind vane 23 acting to close or open a valve in the source of reduced pressure 39. According to the Provisional Specification, the aileron and alula controls may be associated on the same control lever and manual means provided for connecting them together or rendering them independent of one another.