Patent GB-669496-A (GB)
Title: Improvements in or relating to aircraft
IPC: B64C13/00
Filed: 1949-10-12
Abstract: 669.496. Control of several motors. SAUNDERS-ROE, Ltd., and SWAIN, A. E. Dec. 22, 1950. [Oct. 12, 1949] No. 26220/49. Class 38 (iii). [Also in Groups XXX and XXXIII] The transmission of a power-operated aircraft control surface includes a link which is normally rigid but which, in an emergency, such as power failure, can be extended or contracted to move the surface into the trailing position. As described, the link is in the form of a screw jack operated by an electric motor arranged to be energised automatically upon failure of the main power source. Fig. 1 shows the system applied to the elevators, rudder and ailerons, which are each divided into a number of sections as described in Specification 645,911, [Group XXXIII], the main hydraulic power units 18, 118, 31, 131, 43, 143 being of the type described in Specification 619,984, [Group XXXIII]. According to the Provisional Specification, such a link may also be fitted in the flap-operating mechanism. In the case of the elevators emergency-operation jacks 23, 123 are fitted to each of the sections, but in the case of the rudder a jack 23 is fitted to the lowest section only, while jacks 23, 123 are fitted to the two centre sections only of each aileron. As shown in Fig. 3, each control surface 22 pivots about an axis 56 . under the control of a rod 221 and lever 21, the latter being connected to one end of the jack 23, the other end being pivoted to one end of a link 59, whose other end is pivoted at 60 to the control surface. In the event of power failure with the surface displaced as shown, the latter may be returned to the neutral position by extension of the jack 23 upon actuation of the electric motor 55. The circuit arrangement for one control surface is shown in Fig. 6, the motor 48 for the main hydraulic power unit being controlled by a switch 66 in the cockpit. The jack motor 55 comprises two windings connected to bus bars 82 connected to two phases of a three-phase supply, the third phase being earthed. Upon movement of the switch 66 to contact 68 a contactor pull-in switch 69 is energized to close contacts 71 and supply current from terminal 72 through an automatic starter 73 to the motor 48. In the event of failure of the power unit a switch 54 is closed momentarily, thus completing a circuit from terminal 70 to brushes 78 of a pair of drum switches 79 carried by the surface. Depending upon the position of the control surface, the brushes contact the upper or lower conducting segments of the switches and thus energize one of two pairs of centralising relays 80, 81 and the corresponding winding of the jack motor 55. The motor rotates until the control surface reaches its neutral position, when the brushes 78 contact the dead spots on the drum switches 79. Closure of the switch 54 also energises a relay 83 operating contacts 84, 85, the latter of which completes a circuit through a half-wave rectifier 89 to energise a coil 88 and retract the latching plunger 77 for the main contacts 71. and allow them to open to cut off current to the main motor 48. In the case of the ailerons closure of the switch 54 also energizes a motor 86 by which the surface is uncoupled from its associated power unit.