Flight, December 1930
THE SOLDENHOF TAILLESS 'PLANE
A Swiss Light 'Plane Two-Seater
STALLING and spinning are still the two dangers of flying, and in seeking to avoid them aircraft designers may be said to have adopted three distinct means of cure: The Handley
Page automatic wing tip slot (which checks the incipient spin but does not prevent the stall), the "tail-first" or "Ente" lifting surface arrangement, and the "tailless" machine. The Handley Page slots are, of course, well known to readers of FLIGHT. They have robbed stalling of much of its danger, because a machine fitted with them does not flick into a spin when it is stalled. The tail-first or "Ente" ("Duck") principle has been revived in Germany recently by the Focke-Wulf firm, whose latest "Ente" has passed its tests with flying colours and is now passed by the German authorities for passenger-carrying. The tailless type of aircraft was reintroduced by Captain Hill in England some years ago, and Captain Hill has, with the assistance of the Westland Aircraft Works, continued his experiments and researches with machines known as the "Pterodactyl" series. A three-seater machine of the tailless type is now in course of construction at Yeovil.
In the meantime a Swiss engineer by the name of Soldenhof has also been experimenting with tailless aircraft, and has now reached the stage where he is ready to market his machine, one of which is shown in the accompanying illustrations.
Before building his full-size machine Herr Soldenhof had wind tunnel tests made on models, and these indicated that the wing arrangement chosen, i.e., with a pronounced "wash-out" towards the wing tips, has given a perfectly stationary centre of pressure, although the wing section employed is not in itself one of the stationary c.p. types. The fundamental principle of the Soldenhof machine is the same as that used by Captain Hill in his "Pterodactyls," i.e., a pronounced sweep-back combined with a "wash-out," or reduction in angle of incidence from centre of wing to wing tips. The forward, central part of the wing thus reaches its maximum lift before the wing tips do, and the nose of the machine drops before the complete wing is stalled. Tunnel tests on the Soldenhof are reported to have shown that the maximum L/D of the machine is 18, which is a high figure in view of the relatively low aspect ratio.
As marketed the Soldenhof machine will be a two-seater light 'plane, fitted with 40 h.p. Salmson radial air-cooled engine. The tare weight is given as 240 kg. (528 lb.) and the gross weight as 450 kg. (990 lb.). The maximum speed is approximately 100 m.p.h., and the range about 450 miles.
Those interested are advised to write to Mr. C.Guggenheim, The Star Hotel, 30, Charlotte Street, London, W.I.