Patent GB-900835-A (GB)
Title: Improvements in or relating to power-operated flying controls for aircraft
Inventor: MILLARD DENNIS JOHN
IPC: G05D1/00
Filed: 1958-03-20
Abstract: 900,835. Fluid-pressure servomotor-control systems. BOULTON PAUL AIRCRAFT Ltd. May 29, 1959 [March 20, 1958], No. 9009/59. Class 135. In a flying control, a powered control 7b (Fig. 1) has incorporated in it a means of, either, adding rate . damping (i.e. autostabilization) from an auto-pilot (not shown) to one flying surface element 1b alone in addition to the pilot's control via the joystick 3, or, controlling the element 1b directly from the auto-pilot and the flying surface elements 1a 1c and 1d by position feed-back of 1b via the common coupling CC when a weak spring box 6b is locked. The joystick has the usual " feel " springs 4 and 5. Fig. 2 shows 7b in more detail. A floating lever 30 is connected by pivot 31 to another floating lever 26 via a bell-crank 32 (pivoted at 33 and lockable at 37 by a solenoidoperated valve 38) and a link 28 having a spring portion 29. The lever 30 has feed-back from element 1b via links 35 and 36. The lever 26 has its intermediate pivot 27 moved by signals from an auto-pilot (not shown) via a torque motor 52 and a follow-up servo 50, 51. The shaft of the motor 52 and hence the position of the pivot 27 can be locked by members 53, 54 operated by a solenoid 55. Another follow-up servo 24, 25 is connected to lever 26 and this servo rocks the radial piston pump 22 about its pivot 23. The angular position of pump 22 determines the flow of fluid to the ram 20 and hence the position of the flying surface 1b Ram 20 and hence also flying surface 1b may be locked by a valve 44 (having a pilot's warning light 46) when the aircraft is parked. Fluid pressure in a sump 39, supplying the hydraulic system of the flying control, is maintained by a further radial piston pump 40; whose angular position is spring-loaded to the " delivery " position by the pressure this pump generates acting on a piston 43 opposed by a spring 42. When the pilot alone controls the aircraft 52 and 53 are locked and 6b and 37 are unlocked so that his joystick movements via rod 2b are differenced with position of the surface 1b by lever 30, the result fed to servo 24, 25 (via bellcrank 32, link 28 and lever 26) and the surface 1b is moved by the resulting action of pump 22 and ram 20. The surfaces 1a, 1c and 1d are controlled in like manner by their powered controls 7a, 7c and 7d, respectively. There is no feed-back to the other surfaces of the positions of surface 1b since its weak spring 6b isolates it. When auto-pilot stabilization is required, members 6b, 37, 52 and 53 are unlocked, the auto-pilot signal is fed to torque motor 52 and thence to the differential 26 at the pivot 27 via servo 50, 51. Finally, if the auto-pilot alone is to control the aircraft, 6b and 37 are locked while 52, 53 are unlocked. Feed-back from surface 1b now passes via links 35, 36, lever 30, stiff spring box 10, control-rod 2b and common coupling CC to the other control-rods 2a, 2c and 2d. Thus the auto-pilot signals to torque motor 52 control (i) flying surface 1b directly via its servocontrolled ram 20 and (ii) flying surfaces 1a, 1c and 1d via their rods 2a, 2c and 2d and their respective servo-controlled rams by way of position feed-back from surface 1b. The autopilot is automatically switched off to prevent runaway by limit switch 11 operated by the collapsing of spring-box 10. The pilot, if he wishes, has immediate control of three flying surfaces when the auto-pilot is flying the aircraft and by exerting sufficient force to collapse spring-box 10 he can switch the auto-pilot off via 11.