Variable‐pitch airscrews driven through multiple speed gear boxes are controlled by a single lever to provide in one position high speed and fine pitch and in another position a lower speed and coarser pitch. The epicyclic gearing includes an annulus wheel B1 driven from the crankshaft and a series of double planet wheels B2 carried in a frame B3 rigid with an axial extension B4 of the airscrew hub A1. The series of planet gears mesh with sun wheels C, C2 respectively on sleeves C1 and C3 which are adapted to be clutched to the fixed casing D by clutches D1, D2 movable into position by a ring D3 which is actuated by a ring E, which through pivots and levers is movable by a piston K in a cylinder K1 which is coupled by pipes J3, G4 through a control valve H1 with a pressure supply. Branch pipes G3, J2 pass to compartments in the hollow shaft and thence to a cylinder F3 coupled to the blade roots for varying the pitch. The valve H1 is controlled from the cockpit through levers H2, H3.
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