The Rolls-Royce Griffon engine was designed in answer to Royal Navy specifications for an engine capable of generating good power at low altitudes. Concepts for adapting the Spitfire to take the new engine had begun as far back as October 1939; Joseph Smith felt that "The good big 'un will eventually beat the good little 'un." and Ernest Hives of Rolls-Royce thought that the Griffon would be "a second power string for the Spitfire". The first of the Griffon-engined Spitfires flew on 27 November 1941. Although the Griffon-engined Spitfires were never produced in the large numbers of the Merlin-engined variants they were an important part of the Spitfire family, and in their later versions kept the Spitfire at the forefront of piston-engined fighter development. This article describes the Griffon-powered Spitfire variants. Wing types The majority of Spitfires from the Mk VIII used C, D and E wing types. Unless otherwise noted, all Griffon-engined Spitfire variants used the strengthened Dunlop AH10019 "four spoke" pattern mainwheels. With the increasing use of hard-surfaced runways in the post-war years, many Spitfires were either manufactured or re-fitted with, larger mainwheels which were of a "three spoke" pattern. These were used on modified undercarriage legs which had reduced "toe-in" for the axles, which reduced tyre scrub. C type Also known as the "Universal wing" the new design was standard on the majority of Spitfires built from mid-1942. This wing was structurally modified to reduce labour and manufacturing time plus it was designed to allow mixed armament options, A type, B type or four 20 mm Hispano cannon. The undercarriage mountings were redesigned and the undercarriage doors were bowed in cross section allowing the legs to sit lower in the wells, eliminating the upper-wing blisters over the wheel wells and landing gear pivot points. Stronger undercarriage legs were raked 2 inches (5.08 cm) forward, making the Spitfire more stable on the ground and reducing the likelihood of the aircraft tipping onto its nose. During production of the Mk VIII and Mk IX, a new undercarriage leg was introduced which had external v-shaped "scissor-links" fitted to the front of the leg; this also led to small changes in the shape of the undercarriage bay and leg fairings. Several versions of the Spitfire, including Mk XIV and Mk XVIII had extra 13 gallon integral fuel tanks in the wing leading edges, between the wing-root and the inboard cannon bay.