Patent GB-735502-A (GB)
Title: Improvements in combined aileron and landing flap
IPC: B64C13/00
Filed: 1949-09-29
Abstract: 735,502. Fluid-pressure servomotor-control systems. NORTHROP AIRCRAFT, Inc. Sept. 29, 1949 [Oct. 30, 1948], No. 25053/49. Class 135. [Also in Groups XXX, XXXIII and XXXVII] An aircraft control system having separate power-operated control surfaces normally discharging separate functions and including means to move one of the surfaces to co-operate with the other, without interfering with the discharge of its own function, is characterized by pilot-operated control members provided with driving connections from the power units to the control surfaces, one of the driving connections being irreversible while the other provides a lost-motion connection to permit of the conjoint and independent operation of the surfaces as desired. The invention is described as applied to power-operated ailerons and flaps, the former being capable of drooping to operate with the flaps to give a fullspan flap effect. General arrangement.- Each aileron 25, Fig. 1, as described in Specification 735,505, is arranged for alternative operation by a hydraulic actuator 15 of the type described in Specification 701,504, or an electric actuator 67, while each flap 94, Fig. 6, is operated by an electric motor M driving a screw and nut 92, 93. The pilot's control column 2 is connected through a link 9 with a bell-crank 11, the arms of which are connected to a rod 18 controlling the supply valve of the hydraulic actuator and to a rod 31 controlling the switches of the electric actuator. Follow-up links 35, 37 are connected to a second bell-crank 36 carried by the piston rod 14 of the hydraulic actuator. The latter operates the aileron through members 20, 22, 23, while the electric actuator operates through members 65, 64, 23a, the operating linkages being interconnected by a rod 61. The electric actuator is controlled by a series of switches 51, 52-55, which are brought into operation successively by increasing movement of the pilot's control lever, to give a progressively increasing speed of aileron movement (see Group XXXVII). Selective operation of the actuators is controlled by a two-position manual switch 85, Fig. 5, which, when closed selects the electric system and, when open, the hydraulic system. Closing of the switch opens a by-pass valve 86 in a conduit connecting the ends of the actuator cylinder 15 and closes a solenoid shut-off valve 88 to cut off the liquid to the supply valve. A pressure-operated switch 89 is placed in parallel with the manual switch 85, so that the electric actuator is automatically brought into operation if the pressure in the hydraulic system falls below a predetermined value. Flap and aileron operation.-The flap-actuating screw and nut mechanism 92, 93, Fig. 6, is connected by a cable and drum 100, 101 to one end of a telescopic link 105, the other end of which is connected to the bell-crank 11, Fig. 1, which comprises a pair of arms capable of being connected rigidly with each other, or of moving relatively to each other, according to the conditions of operation, Fig. 7 (not shown). During normal aileron operation the bellcrank arms are rigidly connected and the link 105 lengthens or shortens and thus has no effect on the flap-operating mechanism. Lowering of the flap results in rotation of the link 105 by the cable 100, the end-of the link having threaded portions 106 of opposite hands which effect relative movement of the bell-crank arms to displace the control rods 18, 31 and thus effect lowering of the'aileron by whichever of the actuators is in operation. The ailerons may be operated differentially in the normal manner during the drooping movement or in the lowered position, movement of the aileron control rods merely altering the length of the links 105 so that the position of the flaps is not affected.