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Aviation History
1957
1957 - 0502.PDF
504 FLIGHT, 19 April 1957 H.D.M. 105 -Hurel's Aero with Miles' Van ONE of the more remarkable facts-of-life in the aviation busi-ness is that nearly every new aircraft which appears uponthe civil scene is built for a special market—and is sub- sequently found to be highly versatile. The expansion of civilaviation seems to have made the demands of the world's markets less easily predictable rather than more; and this is just as true ofthe "outback" and short-haul field as it is of the current ]et-versus- turboprop controversy. It is still largely the intangibles whichcause aircraft backed by even the best sales campaigns to "catch-on." When (as briefly recorded last week) the Miles H.D.M. 105made its first flight at Shoreham on the last day of March a new civil challenger came a stage nearer fruition. For although theH.D.M. 105 is a purely experimental aircraft designed to put to practical test the remarkable Hurel-Dubois wing, it is the fore-runner of the projected H.D.M. 106 light freighter and transport. This aircraft has been designed to fill a special niche that existsbetween types such as Edgar Percival's single-engined E.P.9, the larger Beaver or Otter, and specialized twin-engined types such asthe Scottish Aviation Twin Pioneer or the DHC-4 Caribou, although both these aircraft are over twice the weight envisagedfor the H.D.M. 106. The Miles company claim that the market for a 3,300 Ib-payload,15-passenger economical light aircraft already exists "in abun- dance"; and a steady demand remains, they say, for the Aerovanupon which the H.D.M. 105 is based. The merit of the 105 lies in the aerodynamic efficiency impartedby the Hurel-Dubois wing of ultra-high aspect-ratio—the worth of which was recognized by Mr. George Miles over two years ago.Yet aerodynamic novelty is allied to such structural simplicity that Miles would expect to offer the 106 for sale at about £30,000. The Anglo-French co-operation which inspired the H.DM.105 is evident in this photograph of the capacious Aerovan fuselage married to the high-aspect-ratio Hurel-Dubois wing. '.__.-: "FLIGHT" PHOTOGRAPHS AND SKETCHES And the efficient wing imparts advantages not only during take-offand landing but (unlike most high-lift-device wings) in cruise con- ditions as well. Particular advantages are claimed for the 106'sperformance at high altitudes and temperatures—features not to be overlooked by charter operators in, for example, South America.They might not really require the complications and weight penalties associated with an STOL aircraft, but would probablydemand a good field performance from small, high-altitude aero- dromes. And it is here that the 106's 600 yd-to-50ft laden take-offdistance and I.C.A.O.-standard single-engined climb would score. But before production—or in this case construction—can begin,customers must be found and the temper of new ideas tested upon the anvil of experience. It is for this reason that the one-offexperimental H.D.M. 105 (virtually a new wing on the proven Aerovan airframe) has been built.It will be used as a vehicle for testing the wing, and as a salesdemonstrator. The aerodynamic design of thewing is the work of Hurel-Dubois of Villacoublay, France, and thesame firm did the tentative scheme drawings for the wingstructure. The remainder of the design, drawing and construc-tion work was done by F. G. Miles, Ltd., at Shoreham, with the costs shared about equallybetween the two firms. The outstanding feature of the wing is its aspect ratio of 20.5(the root chord is only 55in). Such a design, if simple methods of construction are to be retained, requires ample strutting, andthe Hurel design makes use of lift-section struts for this purpose. Flaps and ailerons extend the length of the trailing edge andinboard of the ailerons on the upper surface is a pierced, saw- tooth-ridged spoiler. Interconnected and acting in conjunctionwith the differential Frise-type ailerons, the spoiler assists in com- bating the high aerodynamic damping in roll inherent in high-aspect-ratio wings. When the ailerons are at neutral and the spoiler is retracted the latter's ridged upper edge remains pro-jecting above the upper skin; and the ridges smooth out its action as it comes into play when the aileron is deflected. The wing profile is an N.A.C.A. laminar-flow section, 634-420to a station at the inboard edge of the aileron, tapering progres- sively to a theoretical section of N.A.C.A. 63,-412 at the tip,although (owing to the shape of the tip) this profile is never quite achieved. Outboard of the diagonal strut pick-up the wing has a5-deg wash-out, and the wing outboard of the Cirrus Major engine nacelles has a 3-deg dihedral. Construction of wing and struts is perfectly straightforward.The wing outer panels have a single top and bottom flanged diaphragm spar at 35 per cent chord running throughout theirlength. Between adjacent ribs short Z-section stiffeners are riveted to the spar diaphragm; forward of this is a single-skin torsionbox reinforced by longitudinal top-hat-section stringers. The flanged, pressed ribs continue aft of the main spar and carry therear closing member (which is similar to the main spar) and flap and aileron shrouds. Two additional longitudinal top-hat stringers (Left) The H.D.M.10S at Shoreham five days after its first flight, when it had already completed over five hours' flying and 13 landings. Some minor fairings remained to be added when this photograph was taken.
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