GB555635A - Improvements in or relating to the control of aircraft - Google Patents

Abstract

555,635. Telemotors. ANDREWS, E. J., and LISLE, W. G. Nov. 24, 1941, No. 15137. [Class 69 (ii)] I[Also in Group XXXIII] An aircraft control surface is fitted with a tab and both are conjointly controlled from a common pilot-operated control member, the tab being actuated through a fluid control system embodying hydraulic lock means. The tab may act as a servo-tab to assist the pilot, or, in the case of an overbalanced surface, it may be arranged to counteract the overbalance. A rudder 4 is shown operated directly by cables 10 from a rudder-bar 7. A tab 12 pivoted to the rear edge of the rudder is movable by a double-acting hydraulic jack 15, anchored at 18 to the rudderpost, and connected by pipe lines 25, 26, to cylinders 19, 30 on the ends of the rudder-bar, in which work plungers 23, 24 on pedals 21, 22. Control of the tab is rendered irreversible by the device shown in Fig. 2. Two cylinders 28, 29, connected by a neck 30 are interposed in each pipe-line. Spring pressed non-return valves 34, 34<SP>1</SP> are provided in the smaller cylinders 29, and pistons 31, 31<SP>1</SP> having stems 33, also are pressed by springs against the ends of their cylinders. Branch pipes 36, 37 are arranged as shown. Pressure in the pipe line 25 due to pressure on the pedal 21 displaces the piston 31<SP>1</SP> to the right and its stem opens the valve 34<SP>1</SP> to open one end of the jack to exhaust, the valve 34 in the other pipe line being opened directly by. the pressure to permit fluid to flow to the opposite end of the jack. An elevator is described in which the jack for moving the tab is actuated by fluid displaced by a piston in a double-ended cylinder the piston bemg connected to the control lever, and the cylinder being connected to the elevator by linkage. Centralizing springs may be provided in the cylinders 19, 20, rudder bar 6, control surface 4 or jack 15. Should the cables 10 break, the rudder can still be actuated by the servo-tab, the rudder bar having limit stops or being fitted with a locking device. Ailerons and flaps may be similarly actuated. The hydraulic circuit may be provided with a temperature compensator comprising a spring-loaded piston, acting upon a reservoir of liquid to compensate for any contraction of liquid in the pipe lines at low temperatures. A pressure relief valve may allow for expansion.