GB516622A - Improvements in or relating to the control of aircraft according to air speed - Google Patents

Abstract

516,622. Fluid - pressure servomotor control systems. SMITH & SONS (MOTOR ACCESSORIES), Ltd., S., and MEREDITH, F. W. June 14, 1938, No. 17705. [Class 135] A servo-motor device for controlling the air speed of aircraft of the kind in which the variations of speed vary in dynamic pressure has this pressure balanced against an opposing fluid pressure. In the form shown a control surface, such as an elevator 23, is adjusted to maintain the air-speed by a control member 10 subject to pressure produced by motion through the air, e.g., by a Pitot head 13, which pressure is opposed by a fluid pressure loading, such as air supplied from a centrifugal pump 15. An electric motor 29 may drive this pump either at a constant speed determined by a rheostat 31, when the pressure produced will vary with the air density and a tachometer 32 may serve to indicate the desired true air speed for which the rheostat has been set, or at a constant torque determined by a constant current device in the motor circuit, when the aircraft will be maintained at a desired " indicated air speed. The diaphragm 10 is connected to a piston valve 17 controlling compressed air from a supply pipe 19 to a double-acting servo-motor 21 connected to the elevator 23 and to the valve seat 18 by a pivoted lever 25, and a dashpot 24 and spring 28 provide for recentring of the valve seat and diaphragm after each variation.