Ten years of design and development led to the adoption of the Fairey Gannet, a highly successful three-man aircraft built around a most unusual engine. The Armstrong-Siddeley Double Mamba coupled turboprop engine boasted two independent power sections driving separate propellers.Additionally. Fully armed with torpedoes, depth charges or rockets the plane had a maximum speed of 311 mph and a 662 nautical mile range. Fully ten years after the initial specification, the Fairey Gannet reached the active fleet, in service with HMS Illustrious, HMS Ark Royal and HMS Eagle. Eventually, 255 of the up-rated version (Gannet AS Mk4) satisfied the Fleet Air Arms’ need to replace aging Fireflies and Avengers.