Patent GB-645166-A (GB)
Title: Control of multi-engine aircraft
IPC: G05G9/00
Filed: 1948-04-22
Abstract: 645,166. Controlling aircraft. ARMSTRONG WHITWORTH AIRCRAFT Ltd., Sir W. G., and ELLIOTT, F. R. April 22, 1948, No.11065. [Class 4] In an aircraft having reversible-pitch airscrews, driven from different engines, on opposite sides of the centre line of the aircraft, in which each throttle lever is movable in opposite directions from a predetermined closed position to accelerate the associated engine, means are provided for automatically reversing the pitch of the associated airscrew when the throttle lever is being moved through the said predetermined closed position, and an automatic interlock is provided between the throttle levers whereby, as they are being moved from the forward-pitch position towards the reverse pitch position, neither can be moved indepedently of the other beyond the predetermined closed position (the throttle levers then being moved substantially equally in the accelerating direction with the airscrews in reverse pitch) for a predetermined movement. Each throttle lever 10 is integral with a disc 16 provided with an arcuate slot 22 engaging a fixed stop 23 and is mounted for rotation about a shaft 15 upon which is revolvably mounted a sleeve 29 to which are attached levers 28 each carrying a trigger 25 formed with a projection 31 arranged to engage a recess 32 in each disc 16. Each trigger 25 is urged in an anti-clockwise direction by a spring 26 and when either throttle lever is moved to the closed position 11 from the "full power (forward) position the appropriate catch 31 enters a recess 32. Such movement of the catch causes an abutment surface 34 thereon to clear a fixed stop 35 which would have prevented the movement of the arm 28 in the same direction as the throttle lever 10. Since the levers 28 are interconnected by the tube 29 neither throttle lever can be moved past the " no power (reverse) " position 13 independently of the other. When the throttle levers both occupy the latter mentioned position they may be moved in a clockwise direction to open the throttles and at this point a tail 40 on each trigger 25 engages a fixed stop 41 to disengage the catches 31 from the recesses 32 to permit differential movement of the levers 10. When the throttle levers are being returned from the " full braking " position to the " no power (reverse) " position 13 anticlockwise movement of the levers 28 is prevented by a face 43 of each trigger 25 engaging the stop 35 as shown in Fig. 2, until both of the levers 10 occupy the position 13 and the catches 31 enter the recesses 32 to ensure that both throttle levers are moved in unison through the idling position 11 to the " full power (forward) " position. Attached to each disc 16 is a toothed segment 17 engaging with a pinion 18 secured to a disc 19 which has pivoted thereto a link 20 connected to a lever 21 to control the opening of the engine throttle. The links 20 are arranged to be in a dead centre position when the levers 10 are in the idling position 11. Each disc 19 is formed with a cam surface 53 arranged to depress a plunger 51 to actuate an airscrew pitch reversing micro-switch 50, visual warning being provided by a lamp 63. To ensure that the airscrews are not put into reverse pitch before the aircraft lands a stop 58 fast with each disc 19 abuts the end of a lever 59 which is rocked out of engagement therewith by a link 61 actuated by an electric or hydraulic servo device 60 responsive to landing pressure on the undercarriage. A visual or audible warning device 55 is operated by a cam 56 which may be connected to the flap control lever so that if the flaps are set to land with the undercarriage retracted the warning device will be operated.