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Aviation History
1953
1953 - 0456.PDF
452 FLIGHT, 10 April 1953 THE WINNING TWO-SEATER . . . t upwards—as in the Messenger and Gemini—and are secured in the closed position by shot-bolts attached to the coaming longerons. The designers chose such a canopy on account of the good vision in all directions thereby obtained, particularly when taxying or when flying in the circuit or at low altitude. Each pilot is provided with a direct-vision panel, and a crash pylon is envisaged immediately behind the seat. The sketch on the next page shows well the layout of the cabin, which, besides being compact and suitable for club and pleasure flying, has been designed to be comfortable for all heights of pilot between 66in and 79m. Tail Unit,—Both vertical and horizontal tail surfaces employ a single spar with ply web and spruce boom forming a torsion-box with a ply-covered leading edge. The spars of the fin and tail- plane are located just forward of the rudder and elevator hinge lines, the fin being built integral with the rear fuselage, and the tailplane being a bolted attachment to the extremities of the upper fuselage longerons. Mass-balancing is provided in short horns at the tips of the rudder and elevators. Undercarriage.—A fixed, nosewheel-type undercarriage was adopted, this being considered the best way of meeting the specified cross-wind taxying requirements. Two types of leg, one incorporat ing air-oil shock-absorbers and the other using springs with a friction damper, were examined. The latter—shown in the draw ing on this page—obviates the need for maintenance, at some weight penalty. Large, low-pressure tyres were chosen to permit operation from poor-quality fields, and spats were approved on the ground that they increased cruising speed and range by 8 per cent. Notwith standing this surprising figure, the judges felt that spats were not desirable features, especially as the design was to be suitable for a training aircraft as well as a tourer. The square-section head of each main leg engages in a bracket on the fourth wing rib on each side, the leg being further secured to the bracket by a wrap-over band. The nose-leg has been designed to be capable of manufacture either as a duralumin cast ing or a welded-steel-sheet assembly; it is steered by the rudder bar. Engine Mounting.—The Blackburn Cirrus Minor four-cylinder inverted in-line engine is supported by a welded-steel-tube struc ture made in two separate assemblies, one on each side being hinged to the firewall. The engine could therefore be lowered into position and the mountings swung round against it on each side. The sheet metal cowling is quite conventional, and it embodies pressed-in fluting for added stability. Flying Controls.—The lateral controls constitute one of the few really novel features of the design. Novel, that is, as far as fight aircraft are concerned, for the same sort of system has been used with success on both the Boeing B-47 and the SAAB-29. Basically, the design provides for normal ailerons outboard, and lift flaps inboard; but the latter surfaces are also capable of differen tial movement—over a reduced angular range—to assist the ailerons in a turn by inducing sidewash on the fin in the direction assisting the turn. The designers claim that the layout permits a true turn (i.e., no slip or skid) to be made at any angle of attack or speed, without the use of rudder. This is brought about by the manner in which the fin side-load balances the aileron drag. At the same time, higher rate-of-roll for a given aileron deflection or stick-force is expected. Particularly intriguing is the linkage operating these trailing- edge surfaces. As seen in the drawing (p. 453), the wing houses a rigid torque/push-pull tube which is attached to the ailerons and flaps via eccentrics and skewed toggle links. Lateral movement of the control column is transmitted through a torque tube and bell-crank lever and finally results in a unified reciprocating motion of the tubes in the wings. This causes the skewed toggles to operate both the ailerons and the flaps differen tially, the latter having about half the angular deflection of the true ailerons. Movement of the flap lever actuates a chain and splined sprocket floating on the main wing-tubes in order to provide for the recipro cating motion of the latter. The sprocket rotates the wing tubes and thereby causes the flaps and ailerons to move down to their fullest extent under the influence of the small eccentrics. When the flaps are fully down the latter are at "top dead centre" and thereby transmit no torque to the wing-tubes. The construction of the wing and tail control surfaces can be The honeycomb is a paper structure sandwiched between thin layers of ply. The paper honeycomb is replaced by wood blocks at points of concen trated load. clearly studied with the aid of the diagrams. In all cases, a ply spar web and spruce booms are shown used in conjunction with a ply nose skin. The ailerons are sealed by a fabric strip and are mounted on commercial machined-butt hinges. The inner end of each flap is ply-covered and filled with a paper honeycomb, thus permitting its use as a walkway. Beneath the fuselage is a small split flap, the lower surface of which is entirely ply-covered. The control movements for the tail surfaces are taken, from idling levers under the baggage compartment, through push-pull Fin ond rudder part-section, showing rib-construction and sealing strips. (Right) The undercarriage shown here is that employing springs and friction dampers. The nose leg, which is steerable from the rudder bar, employs a similar type of construction. Large, low-pressure tyres are specified. (Below) The centre fuselage is a straightforward wood structure, although a note of novelty is introduced by the use of wood/paper honeycomb (shown shaded) seats, floor and luggage bulkhead. TUBE M DIA WELDED BOTH ENDS HALF CLAMP AND BRACKET BOLTED TO WING RIB KTHICK RUBBER PHOS. BRONZE BEARING
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