Patent GB-568080-A (GB)
Title: Improvements in control arrangements for aircraft power units
IPC: B64C11/30
Filed: 1943-07-21
Abstract: 568,080. Controlling aircraft power units. DE BAVILLAND AIRCRAFT CO., Ltd., PARKES, J. J., and DURBEC, E. R. July 21, 1943, Nos. 11911/43 and 15654/44. [Classes 4 and 114] An aircraft having one or more engines on each side and means for reversing the pitch of the airscrews, has an operative connection between the pitch-reversing control mechanism and the throttle control connections, such that when the pitch of the airscrews is negative the throttle control connections are changed to cause the throttles to be actuated in a manner which is the reverse of that in which they are operated when the airscrews are in positive pitch. By this means the pilot is enabled to counteract any turning of the aircraft after landing with airs crews at negative pitch by throttle control movements similar to those which would normally be employed with positive pitch airscrews. In the construction according to Figs. 1 and 3, the throttle lever 10 is connected by means of an endless chain 12 to a rotatable drum 14 provided with a toothed arc 16, the latter engaging one of two spaced pinions 18, 20, which mesh with a rack 26 connected to the engine throttle arm 28. During normal movements of the throttle lever, the toothed arc 16 engages with the pinion 18, but upon moving it to the extreme rearward position shown, to reverse the pitch of the airscrew blades, the arc 16 meshes with the second pinion 20, and movements of the throttle lever from the rearward position then have the reverse effect to normal movements of the lever. Reversal of blade pitch is initiated by the closing of a switch 32 by a cam projection 34 on'the drum 14, thus energizing a solenoid 36 to operate a valve associated with hydraulic pitch-control mechanism 38. Return to positive pitch is effected by energizing a second solenoid 40, the circuit of which includes a switch 42 having a holding solenoid 43 energized by the closing of a pressure-operated switch 44. A tooth 46 on the drum 14 rotates a cam 47 to close the switch 42 during the return movement of the drum, immediately after the cam 34 has released the first switch 32. The tooth 46 operates the switch 42 through a spring-loaded pawl 48 on the cam 47, the tooth passing beneath the pawl during the counter-clockwise movement of the drum. The switch 42 is opened at the proper time by the opening of the switch 44 in the holding solenoid circuit, a spring 49 returning the parts to their original positions. According to a modification (not shown), the rack 26 may be dispensed with, the pinions 18, 20 meshing with each other and each being directly connected to the lever 28. 'In the arrangement shown in Fig. 4, for a twin-engined aircraft, the throttle levers 10 are connected to the engine throttle arms 28, 29 by hydraulic cylinders 56, 58 through a four-port valve 62. The latter is actuated by the cable 82 operating the pitch-change control mechanism 86 through a control lever 84. Reversal of airscrew pitch causes rotation of the valve 62, the ports 76, 78 of which reverse the connections between the respective throttle levers and engines. According to the construction shown in Fig. 6, similar reversal of the connections between the throttle levers 10 and engines 50, 52 is effected by longitudinal movement of a sleeve 102 carrying three clutches 96, 98, 100, through a pivoted lever 108 operated by the cable 82 of the pitchchange mechanism 86. In the normal position shown, the left-hand throttle lever 10 is connected by the clutch 96 to the shaft 11, and the right-hand lever to the shaft 13 by the clutch 98. Movement of the clutch assembly to the right causes the left-hand throttle lever to engage the shaft 13 through clutch 100, sleeve 102 and clutch 98, the right-hand lever being connected to the shaft 11 by the central clutch 96.