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Aviation History
1945
1945 - 1726.PDF
AUGUST 30TH, 1943 FLIGHT S THIS WHAT THEY WANT? entirely the expressed wishes of potential customers. But theyknow from experience just how far they can go, at the present stage of aeronautical development, if the result is to be popularwith their sales department. It has to be remembered, too, that the more unorthodox the design, the longer it may taketo "work out the bugs " so that it can be placed in the hands of the customer with confidence on both sides of the counter.And with all available design and engineering talent serving the war effort until now, there has not been much chance to getto work seriously on peacetime projects. Nevertheless, the Piper concern has evidently managed todo quite a bit in this field, for their experimental " Skycoupe " has already flown in prototype and is now undergoing itsdevelopment tests. As will be seen from the first glance at the cutaway drawingby Budd Stone, the Piper Skycoupe is a twin-boom low-wing pusher type fitted with a four-cylinder horizontally-opposedair-cooled engine housed behind the pilot and passenger and contained within the fuselage. This is a complete breakawayfrom pre-war Piper standards and so is the constructional method adopted. i It will be seen that although the engine has been mountedlpy enough in the fuselage to keep the e.g. in a reasonable position, it is set at an inclined angle and drives a high-positioned propeller through a shaft and gear box, thus making A horizontal control column and neatly arranged instrumentpanel are attractive cabin features. The starter button is on the extreme left behind the wheel and the smaller pedal toright of rudder controls is the brake. Dial needles all advance clockwise. possible a very short tricycle undercarriage, the main wheelsof which are retractable. This layout introduces a commend- able safety feature on the ground (the right place to startpursuing safety), for not only does it make it next to impossible for anyone to walk into the airscrew,ducked away between theprotecting booms as it is, but it gives the pilot a field of "t'jaibility when taxying, which is even better than that providedin the average motor car. Moreover, the low tricycle under- carriage and a wide car-type door on each side and in frontof both wings and airscrew make it beautifully easy to get in and out of the little side-by-side two-seater cabin. Womenpilots and passengers should particularly appreciate this feature, though airfield personnel may secretly regret the lossof entertainment provided with earlier types by the combina- tion of a loftier cockpit, a playful slipstream, and feminineskirts. Safety and convenience in taxying are also enhanced by the steerable nose-wheel (non-retractable) which the sketchshows to be linked to the wheel instead of the rudder pedals. There are two advantages in this; the aircraft is steered likea car when being handled on the ground, and, more important still, the rudder can be freely used to correct a dropping wingwhen landing while the nose-wheel is held straighUiu readiness for the touch-down. In fact, the safety aspect here goes evenfurther, since the knowledge that turning the control wheel would also turn the nose-wheel out of line just when contactwith the ground was imminent should discourage the novice pilot from any foolish attempt to lift a dropping wing withan already stalled aileron. Turning now to safety in the air, the Piper Skycoupe aims at non-spin characteristics as a built-in feature by the ptre-vision of fixed slots ixi the leading edge of the wings; these extend for almost the entire span in the experimental proto-type, but the test flights may result in their being considerably modified or even eliminated altogether from future models.The reason for this is that, with the high-lift type of aerofoil used, it may be found that the built-in slots" give BO littleadditional advantage that their extra weight, drag and cost are not justified. That, however, remains to be discovered. The good visibility already mentioned.as a safety factorin taxying is, of course, an even greater boon in the air. The side windows extend a fair way into the curved roof, leavingonly a very narrow "blind spot" immediately above and behind; at least three-quarters of the surrounding atmosphereis reassuringly exposed to the pilot's gaze. Incidentally, none of the windows open on the prototype; passengers being whatthey sometimes aie, the risk of a thoughtless companion tossing some unwanted object out into the airscrew's pathhas thus been anticipated. But later production models may provide a small " no-draught" type of window with a remov-able screen on the pilot's side. This would permit him to stick his head outside if some emergency condition demanded it.and in any case the pilot (even an amateur, "Indicator"!) could surely be trusted to remember he had a " fan " spinninground just behind him. Another safety feature, though less obvious, is the placingof the instrument panel well forward so that, in the event of a crash-landing, the occupants will be less li'-ely to collideforcibly with it. The neatness of the instrument panel and the controls will be appreciated from the accompanyingphotograph, while an excellent little feature is that all the needles on the large, easily read dials move clockwise, thuspreventing any possible confusion. Added to this mental comfort in the cabin's equipment is the physical ease of a46m. cabin width with ample leg room for six-looters, and sponge rubber scat cushioning. Spot-Welded Skin Constructionally, the Skycoupe has a metal chassis-typefuselage, the main component of which is an "A" frame of, I-section beams. The aluminium skin of the body is spot-welded to angle stringers of the same alloy; the two-spar steel tube centre-section is bolted to the " A " frame, and carriesthe welded steel tubular and channel frame on which the engine is mounted. The booms are built up of two over-lapping halves and are anchored to the front and rear spars of the centre-section. The spacing of the nuts securing the twohalves of the booms increases in stages from 2iri. at the front end to 6in. at the tail, which is also a metal structure. Anunusual feature in the taii unit is that a '' stabilivator'' (their lovely word for this one-piece movable aerofoil) takesthe place of the conventional tailplane and elevators, and except for a sheet .aluminium leading edge is fabric coveredlike the rudders. The fins have an aluminium skin. Outer panels of the cantilever wing are built up with twowooden spars and spruce truss-type ribs. A light gauge aluminium alloy skin takes the drag loads; the ailerons andflaps are fabric covered, except that the latter have aluminium leading and trailing edges. Finally a word about the power plant. This is a flat-tourFranklin 4ACG-119 rated at 113 h.p. at 3,500 r.p.m. at sea- level. A stiff, well-braced, large-diameter tapered housingencloses the shaft drive to the gear box, which has a 0.7 to r ratio. This gear box is air-cooled from a small duct just infront of the airscrew on top of the cowling. The engine is air-cooled from ducts in the leading-edge roots, the flow ofair being led past the cylinders and an oil radiator and out behind the centre-section. As the engine's exhaust is carriedinto the same outlet, a fair degree of suction is set up here, which assists the flow of, cooling air past the cylinders. Anelectric starter is operated from the dash. No performance data are available at present as tests, whichmay call for modifications, are not yet completed. " It seems that among the inevitable crop of " headaches " en-countered during the evolution of this very interesting (not to say encouraging) design, three of the worst were: contrivinga satisfactory method of attaching the booms to the centre- section spars having due regard for weight and cost, linkingthe rudder and "stabilivator" controls in the cabin with the tail surfaces without unwelcome complication, and adequatelycooling the engine. • Problems one and two were, in .fact, closely related to eachother, because the method adopted to secure the booms to the centre-section spars had to leave adequate room for the controllines to pass through on their way aft. However, these and other little snags were finally overcome by the application ofAmerican ingenuity and, who knows, a few ice-packs.
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