Abbott-Baynes Scud 3

Auxiliary
Role	Motor glider
National origin	United Kingdom
Manufacturer	Abbott-Baynes Sailplanes Ltd
Designer	Leslie Baynes
First flight	8 August 1935
Number built	2
Unit cost	₤250
Developed from	Abbott-Baynes Scud 3

The Carden-Baynes Auxiliary was the first motor glider with a retractable engine and propeller; it is known as the Abbott-Baynes Scud 3 when engineless. Both aircraft, built in the mid-1930s, were still flying in 2010 as pure sailplanes.

Edward Abbott and Leslie Baynes had already separately designed and built sailplanes when they joined forces in 1931 as Abbott-Baynes Sailplanes to produce Baynes' Scud I and II designs. The idea of adding an engine to a sailplane to make it self-launching, but mounted in such a way that propeller and engine could be retracted at altitude to produce an aerodynamically clean glider came from Sir John Carden, who had already collaborated with Abbott and Baynes on other projects. Baynes' Scud 3 was designed specifically to include such a launching aid but was also capable of high performance engineless flight. Without an engine it was known as the Abbott-Baynes Scud 3; with the engine, as the Carden-Baynes Auxiliary. Since the engine could be removed or retrofitted the nomenclature sometimes became confused. The Auxiliary is historically significant as the first sailplane with a retractable engine and propeller. CG Grey, respected editor of The Aeroplane, wrote after the first flight of the Scud 3, piloted by Dr Dewsbery "Dewsbery now holds the certainly unique position of being the first aviator to retract his motor and airscrew while flying."

The Scud 3 was an advanced sailplane in its time, all wood and with a long-span wing with heavy taper on the leading edge. The airfoil section was designed by Baynes and varied from the wing root outwards. At the centre it had a flat undersurface, making the wing thick and easy to strengthen as well as reducing wing root interference drag. Outwards, as thickness, chord and incidence reduced, the lower surface became increasingly concave, producing reflex camber. These features were intended to ensure that the stall started at the centre of the wing rather than at its tip. The ailerons were of the differential type. The wings were readily demountable for transport.

The fuselage was flat sided and plywood covered apart from near the nose; upper and lower surfaces were curved and again ply covered. The rounded nose was built up with a double layer of narrow spruce strips placed diagonally. The single cockpit was well ahead of the wings and their mounting pylon had a fairing which extended aft of the trailing edge and contained the engine. At the rear there was a tall fin with an unbalanced rudder. The tailplane was mounted about one third of the way up the fin, carrying split elevators; like the wings it could be removed for transport. The undercarriage was just a single wheel mounted partly inside the fuselage.

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