Patent GB-707388-A (GB)
Title: Systems for the actuation of control surfaces to stabilise and steer dirigible craft
Inventor: MEREDITH FREDERICK WILLIAM
IPC: G05D1/00
Filed: 1950-11-09
Abstract: 707,388. Fluid-pressure servomotor-control systems. SMITH & SONS (ENGLAND), Ltd., S. Jan. 11, 1952 [Nov. 9, 1950], No. 27455/50. Class 135 A system for the actuation of a control surface adapted to steer and stabilize a craft, e.g. an aircraft, about a control axis, comprises a servomotor connected to actuate the surface, a control member, e.g. a control column, an instrument, e.g. a gyroscope having its spin and precession axes at right angles to each other and to the control axis giving a first response substantially proportional to the rate of turn of the craft about the control axis, a device giving a second response dependent on the displacement of the surface from its position for a constant course, preferably a long term transient of this displacement, said servomotor being energized in accordance with the algebraic sum of quantities respectively proportional to the force applied to the control member, the said first response and the said second response, whereby if no force is applied to the control member, the surface is actuated to damp motion of the craft about the axis, while if any force is applied to the control member, the craft is caused to turn about the axis at a rate in accordance with that force. To control an aircraft about the pitch axis, the system controls the elevators 10, Fig. 1. The control column 101 actuates, via a link 102, a lever 103 anchored to the aircraft frame 1 by a spring 107 and pivoted to a lever 108 actuated by the gyroscope 11 having its gimbal ring 112 anchored to the frame by spring 114 and having its spin and precession axes at right angles to each other and to the pitch axis. Movement of lever 108 is transmitted via links 115, 132, 121 to a pilot valve 120 controlling a piston and cylinder servomotor 122 which actuates the elevators through rod 124, arm 128 and link 131. Fixed to the rod 124 is dashpot piston 125, the cylinder 126 being attached to link 132 and also anchored to the frame by a spring 119. It is stated that the dashpot device provides the said second response, and the time constant thereof is large compared with the short periods of oscillatory motion of the craft about the control axis. Movement of the servomotor recentres the valve 120 and is also fed back to the column 101 through rod 124 which is pivoted to lever 103. The system for controlling the ailerons 20, Fig. 2, is similar to that of Fig. 1, except that the gyroscope 21 has its spin and precession axes at right-angles to each other and to yaw axis of the craft, and a link 233 extends from the pivot point of link 115 on lever 108 for connection to the system controlling the rudder 30, Fig. 3. This system is similar to that of Fig. 1, except that member 301 constitutes the rudder bar and the gyroscopic control is applied through link 233 from gyroscope 21. When the pilot actuates the ailerons via column 101 and applies no force to the rudder bar 301, the rudder will function to damp yaw oscillation, and will only be moved, via link 233, to control the craft if the actual rate of turn in yaw differs from that demanded Operation of the rudder bar may be required to correct side-slip. In the event of failure of the servomotors, the surfaces may be operated manually by providing stops for the levers 103 adjacent the springs 107. In a modification, no manual reversion in the event of power failure is provided, and the aileron servomotor actuates the link 233 through the dash-pot, whereby displacement of the link is proportional to long-term transient of the aileron servomotor displacement.