549,105. Fiuid-pressure servomotors controlsystems. SPERRY GYROSCOPE CO., Ltd., NISBET, R. H., and GLENNY, A. P. Nov. 22, 1940, No. 16819. [Class 135] [Also in Group XX] For the control of aircraft during flight, an alternative manual and automatic pilot control system is combined with an emergency automatic control system, and includes continuously-acting means urging automatic change-over from manual to automatic control and being positively held out of operation by the pilot during . manual control, the automatic controlling mechanism set into action during emergency automatic control being wholly or in part that embodied in the automatic pilot, but the control initiating means for emergency automatic control about at least one axis of the craft including a primary controlling device other than the primary control instrument of the automatic pilot. As shown, the manual control column 1 is connected by cables 2, 3 to the elevator 4. Cable 2 includes a hydraulic servo-motor piston 6 actuated from a relay valve 32 controlled by a diaphragm 27 in a chamber 28. Opposite ends of the latter have restricted air inlets 29, 30, and are connected by pipes 23, 13 and 24, 14 to ports 11, 12 in a casing 10 subjected to suction pressure. Ports 11, 12 are controlled by a plate 8 connected to a gyroscope. Both plate 8 and casing 10 are pivoted at 9. With normal automatic pilot operation the parts are in the position shown, variation in the attitude of the aircraft causing the gyroscope to act on the plate 8 and thus vary the air pressure on opposite sides of the diaphragm 27 which results in movement of the relay valve pistons 33, 34, servomotor piston 6 and elevator 4. Movements of the latter gives a follow-up action on the casing 10 through cables 44, 45, pulley 46, differential gearing 48 and gear 49. The casing 10 may also be under the control of a rate of turn gyroscope (described below) mounted in a casing 54, the movement of this gyroscope being transmitted to the casing 10 through bellows 73, 74, rack 77 and pinions to the differential 48. Alternative means for controlling the servomotor 32, for use in an emergency, consists of a pendulum 103 carried in a casing 105 which is connected to the relay valve 32 and to the rate of turn gyroscope 54 in a similar manner as in the casing 10. The pendulum device 103 may replace the device 10 by operating a handle 107 to rotate valves 17, 18. Pipes 37, 38 leading from the relay valve 32 to the servomotor 7 have a manual byepass valve 80 and an automatic byepass valve 80<SP>1</SP>. The latter is connected to the shaft of a rotary electric magnet 90 the windings of which are connected through a switch 98 and battery 97 to contacts 95, 96. Contacts 95 are on a slidable ring 93 under the pilot's control wheel 92 to which the contacts 96 are fixed, the contacts 95, 96 being normally held apart by springs 94. A spring 91 holds the byepass valve 801 closed when the magnet windings are de-energized. For normal manual control a byepass valve 801 is opened to enable the control surface 4 to be operated by the handwheel 92. Should the pilot desire to set the apparatus for alternative automatic control the handle 101 is rotated to close the switch 98 so that when the pilot grasps the handwheel 92 he moves the ring 93 to close the contacts 95, 96 to complete the circuit through the rotary magnet 90, whereupon the valve 801 moves to interconnect the pipes 37, 38. Should the handwheel 92 be released the automatic control again takes charge. If the pilot wishes to make the emergency automatic control possible he not only actuates the handle 101 to close the switch 98 but also actuates a handle 107 to interconnect pipes 110, 111 with the pipes 23, 24. Thus when he releases the grasp of the handwheel 92, the control of the servomotor 32 is initiated by the pendulum device 103 instead of by the gyroscopic valve device 8. A warning signal, such as by a lamp 102 is given to the rest of the crew when the emergency automatic control takes over. The handles 101, 107 may be interconnected for simultaneous rotation. In a modification, the handle 107 is replaced by automatic means for actuating the valves 17, 18 if the gyroscope of the normal automatic control system should be disturbed. The means for controlling the ailerons are generally similar to that shown in Fig. 1. In the case of the rudder, however, preferably the system operates to bring the rudder to a central position during the emergency control. The byepass valves 801 for all the . servomotors may be interconnected so as to be operated by a single magnet 90, and all the valves 17, 18 may be ganged together for operation by a single handle 107. The rate of turn gyroscope employed in Fig. 1, comprises a rotor 50 in a gimbal ring 51 oscillatable about a vertical axis. A vacuum is maintained within the casing. Air is admitted to the casing through passages 55, 56 controlled by semicircular plates 57, 58 secured to the gimbal ring shaft 53. Thus, if the gimbal ring 51 turns, one of the passages 55, 56 is open to atmospheric pressure and the other to suction pressure according to the direction of rotation. The pressures in the passages 55, 56 are led by pipes 65, 66 to a pair of bellows (one of which 67 is shown), connected by a rod 69 engaging a rod 70 connected to the gimbal ring shaft 53. If the gimbal ring precesses about its axis the difference of pressure set up in the bellows acts on the shaft 53 to check such movement A modified form of control pendulum comprises an inverted rigid pendulum 125, Figs. 2 and 3, pivoted at 128 in a casing 129 which is journalled co-axially with the pivot 128 in a fixed outer casing 130. The bob 137 of the pendulum has very small freedom of movement between walls 138, 139 of a recess 136 in the casing 129 so that if inclined slightly from the vertical position it engages one of the walls 138, 139 and closes a port 140 or 141 in these walls. The ports 140, 141 are connected by channels in a shaft portion 134 of casing 129 with channels 148, 149 which, if the device is used instead of the pendulum 103 of Fig. 1 are connected to the pipes 110, 111, the casing 129 having gears 150, 151 connected to cables 115, 116 for follow-up purposes. Alternatively the pendulum may control electric contacts instead of air ports. Specifications 416,813, [Group XX], 515,290, 531,388, 538,526; 539,058, 543,455, [both in Group XX], and 545,187 are referred to.