Patent GB-531819-A (GB)
Title: Improvements in device for carrying out aerodynamic braking operated by reversal of the pitch of propellers with variable pitch during flight
IPC: B64C11/42
Filed: 1939-05-08
Abstract: 531,819. Variable pitch propellers ; aerodynamic braking. MATTEUCCI, R. May 8, 1939, No. 13670. Convention date, May 7, 1938. [Classes 4 and 114] Relates to the aerodynamic braking of aircraft by varying the pitch of the propellers. In one form, oil is supplied from a pump 18 through pipes 17, 15‹ and relatively movable ports 15<1>, 15 to a chamber 14<1> to move a piston P against resistance. The piston moves a cross-head 8 which through rods 9, forks 9<1> and arms 11 on the airscrew blades adjusts the blade pitch. Operation of a control 16 connects the chamber 14<1> to exhaust in which case the blades assume the normal propelling pitch. Various adjusted positions may be attained by providing a plurality of ports 15, 15<1> each of which would correspond to a particular pitch when throttling of the oil through the ports balances leakage in the system. A safety valve 19 and a weaker safety valve 22 are provided. In order to effect reversal of pitch for aerodynamic braking a control knob 39<1> carried by a lever 39 free on a shaft 38 is raised to free a detent 50 from the end of a locking quadrant 52 fixed to a casing 44. The lever 39 is connected to an arm rigid on the shaft 38 by a bell-crank lever 53 pivoted on the arm and connected to the lever by a pin 57. The lever 53 is held in contact with the arm by a spring 56. Movement of the lever to the left forces an abutment 58 on one arm of the bell-crank lever down the face of an abutment 59 on the casing 44 to engage in a recess 60 in a quadrant 40 pivoted on the shaft 38, provided that the engine throttle or fuel-control lever which is connected to the quadrant has been moved into the position for minimum engine speed. Further movement of the lever moves the quadrant and through rocker arms closes an exhaust-port 25‹ for and opens a valve 25 whereby compressed air flows from a container 24 through a pipe 25<11> past a valve 27 to the chamber 14<1> to reverse the blade-pitch. Simultaneously the compressed air operates a piston 36 to prevent escape of oil. In order that the engine may quickly speed up, an injector cylinder 61 is filled with oil by movement of a spring-pressed piston 62 which is moved to the right to inject the fuel into the intake manifold by the compressed air or by an arm on the shaft 38. To assume normal running conditions, the lever 39 is moved to the right whereupon the detent moves opposite the end of the quadrant 52 and the abutment 58 disengages the quadrant 52. Further movement of the lever to the right, opens the exhaust port 25‹ and closes an exhaust port 26‹ and opens a valve 26 whereupon the compressed air actuates a piston 32 to open an exhaust valve 28 which communicates with the atmosphere through an exhaust port 28". The lever 39 may be employed for regulating the blade-pitch. Where the aircraft includes more than one engine a quadrant 40 is provided for each engine and the abutment 58 is extended to engage with all the quadrants. The lever 39 carries a cam 46 which co-operates with a follower 48 carried by a spring controlled lever to form a lock. In a modification the abutment 50 carries a projection which forms a detent for the lever before the full braking position is reached. In a further modification, the propellers are controlled electrically, the fuel injector in this case being solenoid operated. Specification 499,514 is referred to.