The British Supermarine Spitfire was the only Allied fighter aircraft of the Second World War to fight in front line service from the beginnings of the conflict, in September 1939, through to the end in August 1945. Post-war, the Spitfire's service career continued into the 1950s.
The basic airframe proved to be extremely adaptable, capable of taking far more powerful engines and far greater loads than its original role as a short-range interceptor had called for. This would lead to 19 makes of Spitfire and 52 sub-variants being produced throughout the Second World War, and beyond. The many changes were made in order to fulfil Royal Air Force requirements and to successfully engage in combat with ever-improving enemy aircraft. With the death of the original designer, Reginald J. Mitchell, in June 1937, all variants of the Spitfire were designed by his replacement, Joseph Smith, and a team of engineers and draftsmen.
The Spitfires with the single-stage Merlin engines used four different wing types, Type A, B, C and D wings, which had the same dimensions and plan but different internal arrangements of armament and fuel tanks. All Mk Is, IIs, and Vs and their derivatives had small, rectangular undercarriage indicator pins which projected at an angle from the upper wing surfaces when the undercarriage legs were locked down, providing a positive mechanical indication that the landing gears were indeed down and locked, since the pilot could not see the landing gear for himself. These were a backup to the indicator lights on the instrument panel, in case the lights malfunctioned or failed. All of these variants used Dunlop AH2061 tyres, mounted on alloy main wheels which had five openings. The fixed, castering tailwheels used Dunlop AH2184 tyres.
Starting with the Mk V, some Spitfires had their rounded elliptical wingtips "clipped" outboard of the ailerons, and replaced by shorter, squared-off fairings to improve low-altitude performance and enhance the roll rate, one area where the Mk V fell badly behind the rival Fw 190. Although these "clipped-wing" aircraft are popularly known as "L.F." versions due to the fact that they were designated "L.F." (i.e. Spitfire L.F. Mk V), the "L" actually refers to the different versions of the Rolls-Royce Merlin engines used, which were optimised for low-altitude performance with "cropped" supercharger impellers (Merlin 45M, 50M or 55M). While many "L.F" Spitfires were given "clipped" wings to accompany the new engine variants, a number still retained the original wingtips.
In the summer of 1939 an early Mk I K9788 was fitted with a new version of the Merlin, the XII. With the success of the trial it was decided to use this version of the Merlin in the Mk II which, it was decided, would be the first version to be produced exclusively by the huge new Lord Nuffield shadow factory at Castle Bromwich.
Chief among the changes was the upgraded 1,175 horsepower (876 kW) Merlin XII engine. This engine included a Coffman engine starter, instead of the electric system of earlier and some later versions of the Merlin, and it required a small "teardrop" blister on the forward starboard cowling. The Merlin XII was cooled by a 70% to 30% water glycol mix, rather than pure glycol used for earlier Merlin versions.
The MkII's B-type wing was structurally an A type modified to carry one 20 mm Hispano cannon per wing, which replaced the two inner .303 machine guns. The retractable underwing landing lamp was repositioned. The cannon was installed in the innermost machine gun bay, next to the wheel well, while the second gun was deleted altogether. The area where the inner guns ammunition trays had been located, outboard of the cannon bay, was converted into a compartment to accommodate the 60-round drum magazine for the cannon. The upper and lower wing skins now incorporated blisters to clear the large ammunition drum (the underwing blisters came in two different shapes). The remaining outer pairs of .303's were not changed at all. Only one armament suite could be fitted to a Spitfire with the B-type wing: Two 20 mm Hispano Mk II cannon, each with a 60-round drum, and four .303 caliber Browning machine guns in the outer positions, with 350 rpg. Alloy-covered ailerons were standardised on this wing type.
In early 1940 Spitfire Is of 54 and 66 Squadrons were fitted with Rotol manufactured wide-bladed propellers of 10 ft 9 in diameter, which were recognisable by a bigger, more rounded spinner: the decision was made that the new propeller would also be used exclusively by the Mk II. This engine/propeller combination increased top speed over the late Mk I by about 6–7 mph below 17,000 feet, and improved climb rate. Due to all of the weight increases maximum speed performance was still lower than that of early Mk Is, but combat capability was far better.
In the early months of 1942, with the clear superiority of the Focke Wulf Fw 190 over the Spitfire VB, there was much pressure to get Spitfires into production using the new two-stage supercharged Merlin 61 engine. In September 1941 the Spitfire Mk III prototype N3297 had been converted by Rolls-Royce at their Hucknall plant to take a Merlin 60, which had been specifically designed for use in the Wellington Mk VI high altitude bomber.
The performance increase was described by Jeffrey Quill as a "quantum leap" over that of the Mk VB and another Spitfire airframe, R6700 was modified to take the new engine. Although design work on the Mk VII and VIII series was under way, these would take over a year to get into production and a counter to the Fw 190 was urgently needed. The Air Ministry made the decision that Mk VC airframes should be converted to take the more powerful engine and, as a result, many of the early IXs were converted Mk VCs which did not have any of the refinements which later appeared.
The performance of the Spitfire MKIX was outstandingly better than the Spitfire V especially at heights above 20,000 feet. On the level it was considerably faster and climbed exceptionally. The MKIX could climb easily to 38,000 feet and when levelled off could then be made to climb in stages to above 40,000 feet by building up speed on the level and a slight zoom. Its manoeuvrability was as good as a Spitfire V up to 30,000 feet and above. At 38,000 feet it was capable of a true speed of 368mph whilst still being able to manoeuvre well for combat.
Although the Mk IX's airframe did not have the aerodynamic and strength improvements, or the modified control surfaces of the Mk VII and VIII, the Mk IX still proved to be an effective counter to the Focke Wulf Fw 190.
In September 1942, the "High Altitude Flight" was set up at RAF Northolt to counter the threat of the high altitude Junkers Ju 86 R bombers. Two Spitfire IXs converted from VCs were stripped of armour, the .303 Brownings and other equipment and repainted in a lightweight PRU blue finish. One of them intercepted a Ju 86R at over 40,000 feet.
Production of the Mk IX finished at Supermarine in June 1943, with production continuing exclusively at the Castle Bromwich factory. Several major and large numbers of minor improvements were progressively introduced to Mk IXs, some of which were used on other Spitfire variants.
The Merlin 61 was phased out early in 1943 in favour of the Merlin 63 and 63A.The new engine had increased power resulting from engine improvements and engine limitations of +18 lbf/(sq in) and 3,000 rpm (5 minute combat). During the second half of 1943, production of the Merlin 63 powered F Mk IX was discontinued in favour of the Merlin 66 powered LF Mk IX. Early production Spitfire IXs suffered from vapour locks in the fuel lines resulting from fuel evaporating if the aircraft was parked in direct sunlight. As a result of this the gun-camera was moved from the port wing root to the starboard wing root and a fuel cooler, fed by a small round air-intake was fitted in its place. This fuel cooler was also fitted to early PR Mk XIs.
Production of the LF Mk IXs, frequently referred to as the Spitfire IXB, initially ran in parallel with the Merlin 63 powered Marks. This version first became operational in March 1943 with the Biggin Hill Wing, comprised at the time of 611 and 341 (Free French) Squadrons. This type was by far the most produced of the Spitfire IX variants, with over 4,000 built. Also introduced in early 1944 was a new Mark II Gyro gunsight. This gunsight calculated the correct angle of deflection to use when leading the target. Its introduction doubled the effectiveness of RAF gunnery and was a major factor in Allied air superiority.
Late production Mk IXs, in common with Mk XVIs introduced a new upper engine cowling which incorporated a distinct bulged top surface; this design was adopted for the Mk XVI to allow for the modified intercooler of the Packard Merlin 266, which had an integral header tank.
The cut-down rear fuselage and bubble canopy, trialled on a Spitfire Mk VIII, was incorporated into very late production Mk IXs. With the cut down fuselage the lower forward fuselage tank capacity was increased to 47 gallons, while the rear fuel tanks were decreased to a capacity of 66 gallons. These were the rarest of the Mk IXs and many of them featured the "clipped" wings. The great majority of these saw postwar service with the SAAF, both in South Africa and in deployment in Korea during the 1950s.
* Images shown are a guide and references only to show how the kit can be assembled allowing for modellers to add extra detail as required