The Supermarine Spitfire was fitted with a series of different wings during its service career. The type of wing generally indicated the armament of the fighter, or the range of guns that a particular aircraft could carry, and was combined with the Mk number to produce a full designation Mk IIb or Mk Vc.
In each case the number of guns indicates the total for the fighter, not the total per wing.
a wing
The Spitfire I was originally armed with eight .303in Browning machine guns, each with 300 rounds. This type of wing was officially designated as the a wing on 15 March 1940, to distinguish between machine gun armed Spitfires and cannon armed aircraft. The vast majority of Spitfires in use during the battle of Britain were armed with machine guns.
b wing
The eight .303in machine guns of the Mk I Spitfire had given it a great deal of punch when it was designed, but when the Germans began to add armour to their bombers the machine guns were found somewhat lacking. Accordingly experiments were made with the use of 20mm Hispano cannon.
This gave it a great deal of punch when it was developed, but when the Germans began to add armour to their bombers, the rifle calibre machine guns lost some of their effectiveness.
The response was to fit the Spitfire with the 20mm Hispano cannon. This poses a variety of problems, not least of which was the size of the cannon. The only way to fit it in the Spitfire wing was to mount it on its side. A second problem was that the early cannons were prone to jam under the pressure of combat. If one cannon jammed, the recoil from the other one was enough to push the Spitfire off course.
The b wing entered service during 1940. No.19 Squadron used it during the battle of Britain, but the cannons were still causing problems. Finally in November 1940 No.92 Squadron was given Spitfires equipped with two 20mm cannon and four 0.303in machine guns. This proved to be a much more effective combination of weapons, and became the standard for the b wing.
c wing
Spitfire F.Mk IX with "c" wing The c wing appeared in October 1941. It was a universal wing that could take eight .303in machine guns, four 20mm cannon or two 20mm cannon and four machine guns. Each cannon now had 120 rounds, compared to the 60 of the b wing. This wing was used on the majority of Mk V Spitfires, normally with the combined cannon and machine guns configuration. The c wing also had the capability to carry two 250lb bombs under the wings, or one 500lb bomb under the fuselage. If machine guns were used, they were used in the outboard position. The a and b wings were not used after the Spitfire V.
d wing
This was a wing used on some photo reconnaissance Spitfires. Instead of guns this wing carried extra fuel, giving the reconnaissance aircraft a range of up to 2000 miles.
e wing
The e wing was a further development of the Universal. It could carry either four 20mm cannon or two 20mm cannon and two 0.5in Browning machine guns. This time the cannon took the outer position and the machine guns the inner. This was partly because it gave more room for machine gun ammunition and partly because the bombs were carried below the inner gun positions, and there had been some problems reported when both cannon and bombs were on the same part of the wing. The e wing appeared in the second half of 1944.
Mk 21/24 wing
The wing used in the Mk 21 Spitfire was significantly redesigned. The leading edge lost its curve, running straight out to the guns. Armament was standardised at four 20mm Hispano Mk II cannon, with 175 rounds for the inboard gun and 150 for the outboard gun. In official documents this
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