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Aviation History
1953
1953 - 1103.PDF
28 August 1953 255 OESSYN 'FLIGHT" copyright drawings FLOTATION BAG M.L. AVIATION PILOTLESS TARGET (45 h.p. Vincent Picador Vee-twin Engine) Weight Span Length overall Height overall Engine r.p.m. Reduction-gear ratio Airscrew diameter Speed at sea level Speed at 10,000ft Duration ... Service ceiling Fuel capacity Maximum diving speed ... Rate of climb (sea level)... 472 lb 12ft 12ft 6in 2ft?+in 5,000 2to1 4ft 6in 203 kt ... 190ktT.A.S. ... 45 min 19,000ft 5.3 gal ... Specification 2S0 kt* 2,000ft/min •A figure of 300-350 kt is expected to be achieved. The control-system is effected with Dessyns, electric motors and a simple linkage. The elevator (top) and the aileron units are shown, the latter being in the wing centre-section. unit, for example, is attached to the front bulkhead at only four points; detachment here, and uncoupling of three electrical sockets and the fuel-supply union, are all that is necessary to remove the complete unit. The engine, a modified form of the Vincent Rapide, and known as the Picador, was described briefly in the article "Power for Ultra-Light Aircraft" in Flight of June 5th this year. It is a 1,000 ex. air-cooled vee-twin, weighing 200 lb and developing 65 b.h.p. at the airscrew shaft. No carburetters are fitted, as it employs direct fuel injection into the inlet pipes. The two jets, situated just behind the inlet-pipe butterfly air-valves, are fed by an injector pump driven from the airscrew shaft. An unusual feature of the engine—though it is normal Vincent motor-cycle practice—is that the cylinders do not he in the same vertical plane. Thus the roller-bearing big-ends are situated side-by-side on the crankpin without the necessity for offset small-ends. For starting, the camshaft has an exposed dog on the starboard side of the engine which engages with the ground electric-starter normally mounted on the launching ramp (or, as the makers term it, launching easel). The engine has a chain primary drive to a right-angled twin- bevel gearbox, the overall reduction being 2:1 from the normal engine r.p.m. of 5,000. The airscrew, made by the Airscrew Company and Jicwood, Ltd., is directly mounted on the output shaft of the bevel box. Dry-sump lubrication is incorporated, oil being circulated by means of the scavenge pump. A common shaft is spring-loaded to hold the butterfly and injector-feed valves open for full-flight r.p.m. An external peg turns the torque-shaft back into the slow-running position for starting and the pre-launch period, and is removed to give full revs just before take-off. The fuel/air ratio is kept constant with varying height by means of a barometriC aneroid control. A centrifugal overspeed governor is connected to the feed injector in order to avoid exceeding the specified in-flight r.p.m. The flight of the aircraft is controlled by a "pilot" on the ground, who is able to transmit by radio a number of com mand signals such as left or right turn, up, down, and level, the degree of each manoeuvre being variable within the aircraft- performance limits. In the aircraft is a radio receiver and an automatic pilot which ensures normal flight stability about the three axes. In addition, the M.L. autopilot interprets the radio command signals from the receiver, and operates the aileron and elevator actuator motors to command an aircraft attitude. It is thus not essential for the aircraft to be within visual range of the pilot for accurate control. Flight can be terminated over a selected landing area by a command additional to those mentioned above; this causes the parachute to be released, and the engine and electrical services to be disconnected. Use of the parachute at an effective height is guaranteed by a pre-set barometric control which enforces a lower safe-altitude limit during flight unless deliberately over ridden by a continued "dive" command. The parachute-release is automatically actuated, also, in the event of an engine failure or loss of radio contact with the ground station. In view of its novel features, this control system is well worth a more detailed study. The ground installation comprises six items: (1) the power unit, (2) the oscillator or tone-generator, (3) a filter unit, (4) a 10-watt transmitter, (5) the ground control box and (6) the aerial; the first four items are mounted as a self- contained group. A 24-volt supply is used. The transmitter radiates a 70-80 Mc/s V.H.F. carrier frequency-modulated by five fixed tones, selection of which is by the switching on the ground control unit. The circuit is so arranged that two selected tones are transmitted simultaneously, energizing two interlocked relay systems in the receiver which are "keyed" to close one output channel, corresponding to a particular command. Thus the receiver is not affected by stray radiation from other sources, since for each command the receiver accepts a pre selected combination of tones. Of the ten possible combinations of two signals, seven are in practice used; the associated com mands being up, down, right turn, left turn, level, parachute release, and "radio hold." This last is automatically transmitted whenever none of the six specific commands is being radiated, and serves to keep the solenoid in the master relay circuit energized. Its de-energizing, and the opening of the relay circuit, causes the parachute release to be actuated. The ground pilot's control box incorporates a miniature con trol column, which by appropriate movement gives the up, down, left, right and level commands. In addition there is a push button to actuate the parachute release, and a dial on which the amount of bank required (up to 45 deg) can be pre-set. The receiver is a frequency-modulated superhet, with a sensi tivity of 30 microvolts for full limiter output. It comprises an R.F. amplifier, a crystal-controlled local oscillator with a separate mixer, two IF. stages, two limitation stages, a Foster Seely discriminator and two A.F. amplifying stages. There are then the five separate tuned circuits of different frequencies which
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