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Aviation History
1947
1947 - 0063.PDF
JANTARY l6TH, I947 FLIGHT 55- LIGHTWEIGHT CANARD Qeneral Details of an American Light Aircraft of Unorthodox Design .. A a recent joint meeting of the San Diego branch ofthe U.S. Institute of the Aeronautical Sciences andSociety of Automotive Engineers, Mr. B. F. Raynes, tooling superintendent of the Rohr Aircraft Corporation, presented general details of a new light aircraft project with which he has been concerned. The venture is de- signated M.O.-i, the letters M.O. signifying Midnight Oiler, a name coined by one of the workers since most of the design work and much of the early shop development was carried out in the small hours. The aircraft is a side-by-side two seater '' tail-first'' type of metal construction, with cantilever wing and '' nose- plane " surfaces, and a retractable tricycle undercarriage. The engine is housed below the wing and aft of the cabin, and drives a centrifugal blower and a pusher propeller at crankshaft speed. Air is drawn in by the blower through slots around the fuselage and is then forced across the engine (for cooling) and through the fuselage into the wings. The wings are sealed to preclude leakage and act as ducts to transmit the air under pressure to full-span discharge slots in the wing upper surface at the 80 per cent chord station. Air under pressure is similarly transmitted to the noseplane, which also has a full-span slot in its upper surface. A farther proportion of the air is mixed with the engine ex- haust gases and delivered under pressure to a discharge slot around the fuselage '' tail'' just forward of the propeller. The propeller is a variable-pitch type and, with the blower, is mounted on a common shaft in which a clutch is incorporated so that, in the event of power failure, the propeller can act as a windmiE and so provide power for operating the blower. Designed as a two-control aircraft, the M.O.-i has no movable vertical surfaces. To exemplify the method of control a turn to port can be considered; the control wheel is turned to the left, and this action partially closes a flap valve in the air duct which serves the port wing. This causes a reduction of C and C, in the left wing and a Wing Spaa Noseplane Span Overall length Empty Weight 24ft. 6ft. 6in. 16ft. 6in. -4951b. Gross Weight Landing Speed Max. Speed Power 1,0101b 40m.p.h 150m. p.h 65b.h.p Wu1 <mi corresponding increase in these values in the right wing, and this is accompanied by a differential jet effect produc- ing yaw in the required direction. Change of C, in each case is said to be effective over the entire semi-span. [It is apparent that the symbol Cp denotes a coefficient of pres- sure, but how it is derived and what is its precise effect, other than perhaps in differential airflow through the slots, is not explained.—ED.] Control of the boundary layer about the wing is claimed to produce several beneficial effects: (i) lateral control may be maintained at high lift coefficients; (ii) favourable yaw- ing moments are produced; (iii) high maximum lift coeffi- cients are possible; (iv) the angle of attack required to attain a given lift coefficient is reduced ; and (v) the profile drag coefficient is reduced. Control Problem Satisfactory lateral control at high lift coefficients has been one of the most perplexing problems confronting air- craft designers. The conventional aileron system produces large rolling moments at high speeds and low rolling moments at low speeds, which is a reversal of the desired condition. In conjunction with these it also has two further disadvantages, namely the production of an adverse yawing moment and the liability of producing a stalled condition over the down aileron wing area. Mr. Raynes went on to say that the lateral control system used on the M.O.-i gives substantially the reverse charac- teristics in that the rolling moments available at low speed are greater than those at high speed, due to the increase in Cp at low speed. A favour- able yawing moment is pro- duced by the differential jet effect. The relationship be- tween yaw and roll can most readily be changed by shift- ing the chordwise location of the exit slot, and, to a lesser extent, by varying its size. High maximum lift co- efficients are beneficial in several ways, not the least being that km landing speeds can be achieved with- out resorting to large wing areas, with their attendant Three-quarter front view of theRohr M.O.-i showing thin wings and end-plate fins. Thenoseplane had not been assem- bled on the snout extensionwhen this photo, was taken.
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