GB757705A - Fluid pressure operated systems - Google Patents

Abstract

757,705. Aircraft controls. ELECTRO-HYDRAULICS, Ltd. June 18, 1954 [April 2, 1953], No. 9277/53. Class 4. [Also in GroupXXIX] In a fluid pressure-operated system for aircraft undercarriages, brakes, flaps, and steering mechanism, two pumps are provided, one operating the port services and the other the starboard services, and the system is so arranged that if one pump fails the other pump will supply fluid to both port and starboard services. The system comprises two pumps 2, 2a, driven by separate engines or electric motors and supplied with fluid from header tanks 1, la; it comprises also selectors 3, 3a, main undercarriage jacks 25, 25a and uplock jacks 26, 26a, nose undercarriage jack 27, nose undercarriage door jack 28 and steering jacks 30. One lever or electric switch operates both selectors 3, 3a. Main undercarriage jack 25 is supplied with fluid from pump 2 through pipes 36, selector 3, filter 33, pipe 37, and non-return valve 23. Fluid returns from the jack through shuttle valve 13, pipe 38, and another filter 33. A pipe 39 connects the selector 3 to the jack 26 via another shuttle valve 13. Pipes 40, 41 of smaller diameter than pipes 37, 38 connect the selector 3 to a second jack 25a and its unlock jack 26a which are operated by fluid from the pump 2 if the pump 2a fails. Jacks 25, 26 are similarly connected to the selector 3a by pipes 40a, 41a in case the pump 2 fails. The emergency operation of these jacks will only lower the undercarriage. Nose wheel jack 27 is connected by a pipe 410 to the pipe 37, a one-way restrictor valve 23b being provided. An emergency fluid supply from pump 2a is available through pipe 36a, selector 3a, pipes 38a, 40a, 146 and shuttle valve 53. Nose undercarriage door jack 28 is connected by a branch 431, a sequence valve 14 and a pipe 430. Pipes 42, 45, 46 and a shuttle valve 63 carry an emergency supply. For emergency operation of jacks 27 and 28, fluid from pump 2a is supplied via branch 146 from pipe 40a. Steering jacks 30 are supplied with fluid through another branch 44, a pressure maintaining valve 15, and a steering selector 4. Fluid from the jacks returns to the selector 3 via pipes 45, 42, 44. Flaps are actuated from the pump 2 through pipe 47, filter 330, flap selector 5, filter 33 and shuttle valve 21. The other end of the jack is connected through a pipe 49, release valve 22, and a filter 330 to the selector 5, and by pipes 50, 77 to the tank 1. The selector is actuated by solenoids. When a valve 520 in the selector is open the flaps are lowered and when a valve 530 is open they are raised. In an emergency, the flaps are actuated by an emergency flap selector 6 and the pump 2a whereby fluid is supplied through pipes 36a, 47a. The emergency supply will only lower the flaps. The pipes of the normal and emergency systems are of the same diameter. Brakes are supplied with fluid by branch pipe 58 via a non-return valve 17, pressurereducing valve 11 and brake control selector valve 10 which may be operated by foot motors 9. An accumulator 8 provides for emergency operation of the brakes. Fluid returns to the tank 1 via pipes 57, 55, 50, 77. Shuttle valves, construction of (Fig. 2). The normal pressure supply acts on a piston 64 and moves it to the right and thereby moves a valve 72 from its seat 73 and the fluid passes through a pipe 74 to the associated jack. When the emergency supply is in use, the fluid moves a valve 70 from its seat 71, movement of the valve 70 causing a valve 72 to close. The emergency supply passes through a pipe 67 and a restrictor valve 68 to the associated jack. Specifications 650,878 and 680,722 are referred to.