GB895922A - Improvements in or relating to aircraft gas-turbine jet propulsion engines - Google Patents

Abstract

895,922. Gas turbine jet propulsion plant. ROLLS-ROYCE Ltd. March 5, 1959 [March 13, 1958], No. 8166/58. Class 110 (3). An aircraft gas turbine jet-propulsion engine comprising a propulsion nozzle with an adjustable member for varying the nozzle area which is movable between a reduced area and a maximum area position, has control means for the adjustable member so that it is moved to the reduced-area position only when the pilot's engine throttle lever is moved to the take-off position and for other settings of the lever, the adjustable member is in its maximum area position. The invention is described with reference to a silenced nozzle of the kind in which fixed hollow lobes 11, Fig. 1, are attached to the downstream end 10a of the jet pipe. The lobes are open at their downstream ends and increase in cross-section at right-angles to the nozzle axis from their upstream to their downstream ends. The interiors of the lobes are open to atmosphere through ports 14 so that air can cool the lobes and then mix with the exhaust gases. An adjustable member 12 preferably of the form described in Specification 849,333 is also attached to the end 10a of the jet pipe. The adjustable member 12 comprises inner and outer flaps pivoted at 18 to the jet pipe end 10a. The flaps are actuated by a ram 19 acting through a piston-rod 20 and linkwork 22, 24. When the lever 27, Fig. 1, is in any position, but that for take-off, the switch 31, Fig. 1, is closed and the coil 34, Fig. 2, energized. The valve member 36 is closed against the action of the spring 37 so that vent 38 is open. The righthand end of the piston valve 45 is thus at atmospheric pressure and the space between the lands 45b, 45c at high pressure so that the piston valve 45 is held at the right hand end of its travel. The high-pressure air conduit 39 is connected through passage 40, space 41 and passage 47 to the right hand side of piston 21, the left hand side of which is connected to atmosphere through the passages 44, 48. The piston 21 is urged to the left and the adjustable member 12 is held in its maximum area position. When the throttle lever 27 is moved into the take-off position shown, Fig. 1, the switch 31 is opened and the solenoid 34 de-energized. The valve 36 closes the port 38 and connects the duct 39 to the right hand end of the piston valve 45 which moves to the right against the stop 49. In this position the left hand side of piston 21 is connected to the high-pressure conduit 39 through passage 40, space 44 and passage 48 and the right hand side of the piston connected to atmosphere through the passages 47, 46. The ram piston 21 then moves to the right and moves the adjustable member 12 to the minimum area position. Specification 895,921 also is referred to.