The Short 31/26 was an unrealised 1927 project to develop an autogyro flying boat to meet UK Air Ministry specification 31/26.The Illustrated Encyclopedia of Aircraft 1983, p.1153Brooks 1988, p.87Barnes 1989, p.455 It is also known by its Cierva design number Cierva C.13Brooks 1988, p.87 or Cierva C.14.
Design On 11 July 1927, the UK Air Ministry issued specification 31/26: Gyroplane boat seaplane (Jupiter engine). The specification called for "the design and construction of a three-seater gyroplane boat seaplane, embodying the principles of the La Cierva autogiro."Air Ministry 1927, p.1
The specification goes on to describe a flying boat with positions for a pilot, observer, and gunner.Air Ministry 1927, p.6 The gunner was to sit in a forward cockpit and be armed with a Lewis gun mounted on a Scarff ring. The aircraft was also to be able to carry twelve bombs that could be launched via an RL tube. A Bristol Jupiter VIII radial engine was specified for the powerplant.Air Ministry 1927, pp.1–2 The aircraft was to be capable of and have a stall speed not greater than .Air Ministry 1927, p.4 In addition to its rotor, it was to have fixed wings.Air Ministry 1927, p.5Lambermont & Pirie 1970, p.135
Development Development was conducted in partnership between Juan de la Cierva and Short Brothers chief designer Arthur Gouge. A two-bladed main rotor was chosen, to be fitted on a pylon above a metal hull. Sponsons were to be fitted for stability on the water.
A model was constructed and tested in the Short Brothers tank at their Rochester factory, but development progressed no further. The experiments showed problems with vibration, which aviation historian Peter W. Brooks notes "would almost certainly have proved unsuperable at this period."
Specifications (as designed)
Notes
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