their proposed aircraft, however, this option was discontinued to concentrate on other efforts. Instead, Fairey approach the engine manufacturer Armstrong Siddeley to develop a new engine based on the existing Armstrong Siddeley Mamba turboprop; the Double Mamba (otherwise known as the "Twin Mamba"). This engine basically comprised a pair of Mamba engines that were mounted side-by-side and sharing a common gearbox. The proposal was enthusiastically accepted and formal design work on the engine stated in December 1945. The acceptance of this proposal enabled Fairey to develop a rather atypical propulsion arrangement for their proposed aircraft, which was normally only possible for a single engined aircraft. Via the use of a pair of coaxial contra-rotating propellers fitted on the nose of the aircraft, various advantages were presented over conventional twin-engine counterparts; one engine could be shut down and its propellers feathered without producing asymmetry and therefore control difficulties. Shutting down one of the two engines in flight would reduce fuel consumption and extend the aircraft's range. On 12 August 1946, Fairey was awarded an initial contract to produce two prototypes; Blackburn also received a competing contract to built its own prototypes. One reason for the ordering of multiple prototypes was so that alternative engines, such as the Napier Nomad, could be test flown, although some of these alternatives would next actually be fitted. Another reason was the relatively radical engine arrangement and the high proportion of original design features incorporated into the aircraft. Into flight On 19 September 1949, the prototype performed its maiden flight from Aldermaston outside Reading, flown by R. G. Slate; this milestone occurred ten months ahead of Blackburn's competing prototype. While some elements of the prototype proved relatively trouble-free, such as the Double Mamba engine, several early test flights had been troubled by flight control difficulties. These issues, such as sharp trim changes, did not delay the next stage of testing, which commenced in November of that year at Fairey's White Waltham facility. On 25 November 1949, the prototype crash-landed during an unstable landing, leading to three months of repairs. On 1 March 1950, flight testing resumed with the repaired prototype. By this point, several of the handling issues had been appropriately remedied along with several other faults, yet difficulties with holding the nosewheel up during landings remained. Two months later, sufficient progress had been made to proceed with a formal assessment by naval test pilots at