Supermarine Spitfire Mk XII

The Griffon had been designed to answer a naval requirement for power near sea level, and Supermarine had been sketching ways of fitting it into the Spitfire since late 1939. The installation changed the aeroplane's profile: prominent blisters over the cylinder banks, a cleaner lower cowling line, a longer spinner and a four-blade propeller. Prototype DP845 flew on 27 November 1941 and passed through two designations before settling as the Mk XII. What caught pilots out was not the extra power but the rotation: the Griffon turned its propeller the opposite way to the Merlin, so the aircraft swung right on take-off and the rudder had to be held the other way round.

With a single-stage Griffon II or IV of roughly 1,735 hp, the Mk XII was excellent low down and unremarkable high up. Every production machine therefore flew with clipped wingtips, which also sharpened the roll rate and gave the mark the liveliest ailerons of any Spitfire so far. Against a Mk IX it was some 23 km/h faster at sea level, yet above 6,100 m the advantage reversed. Early aircraft were built on Mk Vc airframes with a single main tank and a fixed tailwheel; the last forty-odd came from Mk VIII airframes, with wing tanks, a retractable tailwheel and stronger legs.

At a Farnborough demonstration in July 1942 the Spitfire was expected to play the part of the slow benchmark against a Hawker Typhoon and a captured Focke-Wulf Fw 190. DP485, flown by Jeffrey Quill, crossed the line first and inverted the intended result in front of a row of dignitaries. Turning that speed into victories proved harder, because German pilots avoided being drawn into a turning fight below 20,000 ft, but when combat did come the Mk XII accounted for several Fw 190s and Bf 109Gs. Its finest hour arrived in the summer of 1944, when low-level speed made it an ideal flying-bomb chaser: its pilots were credited with 82.5 V-1 kills.

The Mk XII was an interim answer and was treated as one, leaving front-line service in September 1944 after barely two years. The Mk XIV, with a two-stage supercharged Griffon, supplied exactly the high-altitude performance it lacked. Its significance lies less in the hundred airframes built than in proving that the marriage of Spitfire and Griffon worked, and that a 1936 design still had room to grow.