Airfix 1/48th scale Supermarine Spitfire F. Mk.22/24

By early 1942, it was evident that Spitfires powered by the new two-stage supercharged Griffon 61 engine would need a much stronger airframe and wings. The proposed new design was called the Mk 21, which at first displayed poor flight qualities that damaged the excellent Spitfire reputation. The wings were redesigned with a new structure and thicker-gauge light alloy skinning. The new wing was torsionally 47 per cent stiffer, allowing an increased theoretical aileron reversal speed of 825 mph (1,328 km/h). The ailerons were 5 per cent larger and the Frise balanced type were dispensed with, the ailerons being attached by continuous piano-hinges. They were extended by eight inches, meaning that with a straighter trailing edge, the wings were not the same elliptical shape as previous Spitfires. The Mk 21 armament was standardised as four 20mm Hispano II cannon with 150 rounds per gun and no machine guns.

The Mk 22 was identical to the Mk 21 in all respects except for the cut-back rear fuselage, with the tear-drop canopy, and a more powerful 24 volt electrical system in place of the 12 volt system of all earlier Spitfires. Most of the Mk 22s were built with enlarged tail surfaces, similar to those of the Supermarine Spiteful. A total of 287 Mk 22s were built: 260 at Castle Bromwich and 27 by Supermarine at South Marston.

The Mk 22 was used by only one regular RAF unit, 73 Squadron based on Malta. However 12 squadrons of the Royal Auxiliary Air Force used the variant and continued to do so until March 1951. The Mk 22 was also used at Flying refresher schools. In May 1955 the remaining F.22s were declared obsolete for all RAF purposes and many were sold back to Vickers-Armstrongs for refurbishment and were then sold to the Southern Rhodesian, Egyptian and Syrian Air Forces.

The final Spitfire variant, the Mk 24, was similar to the Mk 22 except that it had an increased fuel capacity over its predecessors, with two fuel tanks of 33 gal (150 L) each installed in the rear fuselage. There were also zero-point fittings for rocket projectiles under the wings. All had the larger "Spiteful" tail units; modifications were also made to the trim tab gearings to perfect the F Mk 24's handling. The F Mk 24 achieved a maximum speed of 454 mph (731 km/h) and could reach an altitude of 30,000 ft (9,100 m) in eight minutes, putting it on a par with the most advanced piston-engined fighters of the era.