GB896184A - Aircraft fuel supply systems - Google Patents

Abstract

896,184. Fluid-pressure servomotor-control systems. LUCAS (INDUSTRIES) Ltd., JOSEPH, and ENGLISH ELECTRIC CO. Ltd. March 16, 1960 [March 26, 1959], No. 10510/59. Class 135. A fuel supply system for aircraft of the kind having a pair of engines and a pair of fuel tanks 1, 2 mounted within the wings, each fuel tank incorporating a boost pump 3, 4 for supplying fuel to an engine-driven fuel pump 9, 10 associated with each engine respectively, comprises a pair of fluid-actuated motors 5, 6 for driving the boost pumps 3, 4, respectively, a pair of variable delivery pumps 13, 14 driven by the pair of engines for supplying motive fluid in the form of fuel to the pair of motors, and means for maintaining the output of the variable delivery pumps at appropriately half their maximum output whilst both pumps are in action and for increasing the output of one of the pumps automatically in the event of the other pump failing to function. The variable delivery pumps 13, 14, as shown, supply the motive fluid at half their maximum output to the motors 5, 6 via passages 18, 19 and a solenoid-operated valve 16 provided in a valve housing 15. Also located in the housing 15 are two piston valves 27, 28 which each serve to control the flow of fuel from the upstream side of the pumps 9, 10 respectively to one side of servo-pistons 25, 26 adapted to vary the output of the variable delivery pumps 13, 14, respectively, such as by adjusting the position of a squash-plate; the other sides of servo pistons 25, 26 are each in communication with the output sides of the pumps 13, 14. If, during operation, the pump 13 for example fails, the pressure in the passage 18, which has been acting on the piston 22 of the valve 28 in order to maintain it in the position shown, fails and, thereby causes the pressure in the passage 19 acting on the other side of the piston 22 to move the latter into a recess 18a and thus permit the flow of fuel from the passage 19 into the passage 18. At the same time the valve 28 is moved to prevent the flow of fuel to one side of the servo-piston 26, thus allowing the output pressure from the pump 14 to leak through a restricted orifice 30 in order to cause a pressure balance on each side of the piston; the piston 26 then moves under the action of a spring to effect the adjustment of a squash plate. If one engine begins to use more fuel than the other then the position of the valves 7, 8 may be reversed and also the valve 16 simultaneously moved to its alternative position.