J.Bruce British Aeroplanes 1914-1918 (Putnam)

Hoile Varioplane

  THE name of A. A. Hoile (who was a Dutchman) is probably best remembered as the designer of the peculiar cantilever monoplane wing which, in 1921, was fitted to the fuselage of the little Martinsyde Semiquaver racer. The wing was known as the Alula wing.
  The unusual plan-form of that ultimate Alula wing had two antecedents, the second of which did not appear until after the war. The first was flown on a little monoplane which was far ahead of its time in one respect. This machine was a parasol monoplane known as the Varioplane, and was powered by a 60 h.p. six-cylinder Anzani radial engine. It was flown in 1917.
  Structurally the fuselage and tail surfaces were quite conventional, as the illustration shows, but the wing was a most striking affair. It had a swept-back leading edge and curved wing-tips which tapered to a sharp point. For a considerable part of its span, outboard of the lift-struts, the wing was a cantilever and looked far from safe.
  Most remarkable of all, however - and obviously the aircraft’s raison d’etre - was the use of a variable camber device which closely resembled the split trailing-edge flaps which did not come into general use until nearly twenty years later. It will be seen that the fabric covering of the underside of the Varioplane’s wing was continuous from leading edge to trailing edge, and drooped with the “flaps”. The trailing edge was split, but the upper surface of the variable camber portion drooped in company with the lower.
  Hoile flew his Varioplane at Brooklands, and the machine later went to Farnborough to be tested.