Patent GB-770140-A (GB)
Title: Improvements in or relating to towing apparatus for aircraft
IPC: B64D5/00
Filed: 1955-06-20
Abstract: 770,140. Aircraft towing apparatus. NORTHROP AIRCRAFT, Inc. June 20, 1955 [Nov. 24, 1954], No. 17743/55. Class 4. Aircraft towing apparatus comprises a fluid motor adapted to exert a moment on the cable drum opposing that applied by the cable, and a conduit connected to the motor for supplying fluid thereto from the compressor of an aircraft propulsion unit, the motor acting as a prime mover for reeling in, and as a brake when reeling out. In Fig. 2, the cable 22 proceeds from the drum 18 and is guided by pulleys to the target 23. The cable passes over a device 24 connected by a flexible drive 32 to an indicator 29 showing the operator the length of cable paid out. The cable also passes through a device 26, which incorporates means measuring the target drag and light, ing a lamp 33 through conductor 30 when a predetermined drag is reached and a cable cutting blade 20 operable by an electric motor 25 controlled by a switch 68. The cable drum 16 is connected by a drive 35 to a turbine 21 supplied with working fluid through a pipe 34 in which are an electrically controlled valve 36 and a butterfly valve 37 adjusted by the pilot's control lever 38. When the latter is in its " off " position, switch 63 is in the position shown, conductor 97 is deenergized, and valve 36 is closed. The cable drum is fitted with a disc brake 18 applied by a fluid pressure circuit 43 controlled by a device 42 operable by a reversible motor 41. In the inoperative position, the switches 94 and 96 of a relay 79 are in the position shown, and motor 41 is energized in the sense to apply brake 18, from a source 93 through switches 97 and 94. When the pilot moves lever 38 from the " off " position, he opens valve 37, switch 63 changes over, and valve 36 is opened, and current is fed through switches 67, 65, 52 and 71 to one winding 82 of relay 79. This changes over contacts 94 and 96, thus energizing the motor 41 from source 88 in the sense to release the brake 18. Switch 65 is a reel out limit siwtch opened when the cable left on the reel is less than a predetermined amount. Switch 71 is opened when an " egg " 28 on cable 22 is forced against a plate 73, i.e. at the reel-in limit. This also opens a switch 72 which opens the circuit of valve 36, closing the latter. Switch 52 is an inertia operated overspeed switch, which when operated, de-energizes relay 79, and light a warning lamp 57. A tachometer generator 46 is connected to an indicator 47 on the pilot's dash board. A switch 58 is operated at every revolution of the reel 16, controlling a blinker light 61 to indicate normal operation. For reeling out, the pilot moves lever 38 from its " off " position, which opens valve 36 and releases brake 18. Lever 38 is adjusted until a suitable reel-out rate is attained. To terminate this, the lever 38 is advanced until the pay-out rate is zero, then switch 67 is opened. Relay 82 is thus deenergized, applying brake 18. Lever 38 is placed in its " off " position, changing switch 63, and switch 64 is also closed. A fluid pressure operated switch 44 is arranged to close when the fluid pressure in circuit 43 rises to, say, 1300 p.s.i. Winding 99 of relay 81 is thus energized from source 93. Winding 98 is then energized through contact 84 and switch 64, and relay 81 thus holds itself down until switch 64 is opened. In addition, a solenoid 50 is energized to apply a pawl 48, and winding 83 of relay 79 is energized to release the brake. For reel-in, airspeed is reduced until target drag is low enough for the turbine 21 to reel in, this being shown by light 33. Switch 64 is then opened, and lever 38 advanced until reel-in commences. The cable cutting motor 25 is operable when lever 38 is in its " off " position, switch 63 being as shown.