Penn Smith Gyrocopter

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The Autogyro, otherwise known as a Gyrocopter of Gyroplane, is a simpler type of machine than a helicopter in which the rotor is not powered, but uses the forward motion of the craft to spin the rotor (autorotation) and thus to develop lift. An engine-powered propeller provides the forward thrust, similar to that of a fixed-wing aircraft.

Autogyros were first developed in the 1920s when Spanish engineer Juan de la Cierva created an aircraft that could fly safely at slow speeds. His autogyro was first flown in January 1923, at Cuatro Vientos Airfield in Madrid. De la Cierva's aircraft resembled the fuselage of a fixed-wing aircraft of the day, with a radial engine and propeller in a tractor configuration to pull the aircraft through the air. The term Autogiro subsequently became a trademark of the Cierva Autogiro Company.

The simplicity of the design encouraged many would-be flyers to experiment with this type of craft and various machines appeared, built by commercial enterprises and individual enthusiasts alike. The Bensen Aircraft Corporation of North Carolina, USA, established in 1952, took the concept of the lightweight autogyro (they adopted the trademark Gyrocopter) to the limit. Their Gyrocopters were little more than a frame that the pilot sat ‘on’ (rather than ‘in’), fitted with an engine, a rotor and a very simple control system.

This arrangement was copied by enthusiasts around the world, one of whom was DJ Penn-Smith, who built his machine at Markfield, Leicester between 1969 and 1970. This was powered by a Volkswagen engine, originally 1,200cc, but rebuilt and modified by the designer to 1,584cc Penn-Smith also finished and balanced the two-bladed rotor supplied by Campbell Aircraft Ltd.

There was only one aircraft built: G-AXOM and this was first flown at Wymeswold airfield on 5th April 1970. The Penn-Smith gyrocopter made its first public appearance (non-flying) at Sywell aerodrome on 11th July 1970 and a Permit to Fly (a type of certificate of airworthiness) was issued on 25th August 1970. The rotor diameter was 20 ft, length 9 ft 8 in, empty weight 302 lbs, and all-up weight 512 lbs. Cruising speed was said to be 55mph with a minimum level speed to maintain lift being 40mph. Endurance on a full tank of fuel was 1 hr 40 mins. Retired from use in 1974, G-AXOM was aquired for the Stondon Collection in 1994.

This lot will be available to view at Stondon Museum (SG16 6JN) on Friday 5th June. Although this vehicle will be offered for sale at Brightwells (HR6 0DE) it will need to be collected from Stondon.