GB774389A - Improvements in aircraft fuel systems - Google Patents

Abstract

774,389. Supplying liquid fuel. SELFPRIMING PUMP & ENGINEERING CO., Ltd., MEREDEW, G. C. and MAGGS, M. R. May 18, 1955 [Feb. 18, 1954], No. 4866/54. Class 7 (3). [Also in Groups XXVI and XXIX] In aircraft fuel systems comprising two boost pumps with inlets open to the top and bottom of a fuel tank respectively, the inlet to the upper pump is closed under normal flight conditions and opened under conditions of negative g or inverted flight. As shown, a double-ended centrifugal pump mounted in a tank (not shown) comprises impellers 11, 12 carried by a vertical shaft 14 driven directly by an electric motor or turbine arranged between the impellers or through bevel gears 18, 19 from a motor &c. 20. The height of the pump unit may be varied by exchanging a shaft coupling 16 and a section 17 of the pump casing. Normally, the lower pump only is operative, fuel tapped off from the delivery by a pipe 42 flowing through a valve casing 47 to a bellows 41, or an equivalent piston or diaphragm, whereby a slotted plate 37 is turned anti-clockwise to operate butterfly valves 32 so as to close apertures 31 in a casing 30 surrounding the inlet to the upper pump which is thereby starved of fuel. A weightoperated valve 46 is then in the position shown in Fig. 4, openings 48 and 49 being in communication. Under conditions of negative g or inverted flight, the valve moves to the other end of the casing, the opening 48 is closed, and the opening 49 communicates with an opening 50 leading to the tank, whereby the supply to the bellows is cut off and the valves 32 are opened, so that the upper pump comes into operation. The valve has an axial passage 52 to avoid trapping fuel in the ends of the casing. Pressure in the upper pump when the inlet is closed is relieved by a bleed 54, Fig. 3. The outlets from the pumps are connected to the arms 26, 27 respectively of a Y-shaped conduit, the leg 28 of which is connected to the engine. A flap valve 29 is spring-biased to the position in which it closes the arm 27 and so serves as a non- return valve. The arm 26 has a suction by-pass and refuelling change-over valve as described in Specification 766,447 [Group XVII]. When the lower pump is operating normally the valve 29 is closed, but if the pressure decreases or fails it will allow the upper pump to function. The valve 46 may be movable at will to the other end of the casing when extra fuel is required under normal flight conditions, both pumps being then operative. Specification 688,349 also is referred to.