| Spitfire Mk X | The next Spitfire in the numerical sequence was the PR.X. A total of 16 aircraft were converted from HF.VII airframes, which resulted in delivery being delayed until April 1944 due to the unavailability of suitable airframes. Powered by the high-altitude rated Merlin 64, the PR.X featured the wings of the earlier PR.XI, and a larger oil tank which deepened the underside of the nose cowling. No armament was carried, and some of the armour protection was removed. The PR.X was not a great success, and was removed from front-line service in September 1945. Production: 16 |
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| Spitfire Mk XI | The PR.XI was chronologically well ahead of the PR.X, being derived from the Mk IX. Powered by a Merlin 70, it could climb to 44,000 ft (13,420 m) and attain a speed of 422 mph (679 km/h). The only Mk IX derivative to have a retractable tailwheel, the PR.XI had the broad chord rudder; an enlarged oil tank like all PR variants; and the same leading-edge fuel tanks in the wings pioneered by the PR.IV, bringing the total fuel capacity up to 228 Imp gals (1,036 litres). Deliveries commenced in late 1942, early aircraft being powered by the Merlin 60 series engine. Production: 471 |
| Spitfire Mk XII | Confusingly, the original Mk IV, later redesignated the Mk XX, became the prototype Mk XII: the first of the Griffon-engined production Spitfires. Yet another interim type, the Mk XII was intended to counter high-speed, hit-and-run raids at low level by German fighters, most notably the Fw 190. The Griffon rotated the opposite way to the Merlin, producing a strong swing to the right on take-off, a feature that was not helped by the asymetric radiator, located beneath the starboard wing. Entering service in June 1943, the clipped wing Spitfire Mk XII proved generally superior to the contemporary models of the Fw 190A at low level. Engines for this variant were the Griffon III and IV, and about half the number built had a retractable tailwheel, while almost all examples had the pointed fin and rudder. Production: 100 |
| Spitfire Mk XIII | The next Spitfire in the production sequence was the PR.XIII. This was a departure from previous reconnaisance machines; whereas all previous PR Spitfires had been intended to snoop unarmed at high altitude, the PR.XIII was intended to operate at low level in the tactical reconnaisance role. Due to the higher risk of interception, the A-wing was fitted, with two 0.303 machine guns per wing. Two vertical and one oblique cameras were fitted and the aircraft powered by a low-rated 1,620 hp Merlin 32 engine. Production: 25 |
| Spitfire Mk XIV | The most potent member of the Spitfire family to be used during the Second World War was the Mk XIV, which was based on the Mk VIII airframe strengthened to take the Griffon 65, rated at 2,035 hp. Like the Merlin, the Griffon had been fitted with a two-stage supercharger, and a five bladed propellor was used to convert the power of this engine into thrust. The fin area was increased and an enlarged pointed rudder fitted to improve what would otherwise have been marginal directional stability, and the overall fuselage length increased. Fuel capacity was 115 Imp gals (522.7 litres). Maximum speed rose to 439 mph (706 km/h), rate of climb to 4,700 ft/min (1,433.5 m/min), and service ceiling to 43,000 ft (13,115 m). Take-off weight had risen to 8,750 lb (3,972.5 kg), and the flight controls were correspondingly heavy by comparison with earlier Spitfires. On the other hand, the Mk XIV looked far tougher and more workmanlike when it entered service in October 1944. Surprisingly, it was more manoevrable than the much lighter Mk VIII at all altitudes, mainly due to the ability of the Griffon to haul it around corners at high angles of attack, even though below 20,000 ft (6,100 m) maximum speeds were much the same. If it had a fault, it was that its terminal velocity was limited to 470 mph (756 km/h). This was due to control problems caused by the "aileron float", and was never entirely cured, despite numerous attempts. Early models mounted the C-wing, but the majority carried the E-wing with two .50 machine guns replacing the four 0.303 Brownings. Later production models sported a cut-down rear fuselage and a bubble canopy. A further model carried a fuselage camera in the tactical reconnaisance role; this was the FR.XIVE, which had clipped wing tips. This was also the first Spitfire variant to carry the gyro gunsight. Production: 957 |
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