Spitfire MKIIa

The Spitfire Mk II differed from late production Mk Is in two ways. The aircraft itself used the Merlin XII engine, providing 1,150 hp, an increase of 120 hp over the engines used in the Mk I. This engine could be used with either the de Havilland or Rotol propellers.

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The second main difference is that while the Mk I was built by Supermarine at Southampton, the Mk II was produced in a new giant factory at Castle Bromwich.

This causes inevitable delays, as the new factory was tooled up and gained experience in producing the complex fighter. The first Mk II flew on 24 September. Full production began at Castle Bromwich in June 1940. No. 611 squadron at Digby was the first squadron to receive the Spitfire Mk II in August 1940. The wisdom of the shadow factory scheme that had produced the Castle Bromwich plan was demonstrated in September 1940 when the Supermarine factory in Southampton was bombed, and production there temporarily stopped.

920 Mk IIs were built. Of them the majority (750) were Mk IIas, with eight .303 Browning machine guns while 170 were Mk IIbs, with two 20mm cannon and four .303 machine guns. The Mk II appeared in time to take part in the battle of Britain (see Mk I for more details). Both the Mk I and Mk II were phased out in 1941 in favour of the Mk V. Of the original order for 1000 Mk IIs, the last 80 were built as Mk Vs.


The one major problem with the Spitfire was that it had been designed as a short range defensive fighter. This caused problems when the RAF went on to the offensive, and repeated attempts were made to extend the range of the aircraft. 60 Mk IIas were converted to the long range version by having a 30 gallon fuel tank fixed under the port wing. Three squadrons used this version (Nos. 66, 118 and 152) until it was phased out in March 1942. The extra fuel capacity gave the Spitfire the ability to escort bombers further into occupied Europe, but at the expense of performance – maximum speed came down from 357 mph to 344 mph


Fifty Mk IIb Spitfires were converted to do an air sea rescue role in 1943. They retained the normal two cannon and four machine guns of the Mk IIb, but had a small bomb rack added to carry smoke bombs (used to mark the position of someone in need of rescue). Space was provided within the fuselage for a dinghy and flare pack that could be dropped to marooned sailors or downed pilots.

Mk IIa carried eight .303in machine guns (300 rpg).

Mk IIb carried two 20mm cannon (60 rpg) and four .303in machine guns (300 rpg).
36 ft 10in
29 ft 11in
Merlin XII
1175 (1050 at 13,000 ft)
Max Speed

357 mph at 17,000 ft
500 miles max
395 in combat
37,200 feet
Rate of climb
2.995 feet/minute
Time to 20,000 feet
7 minutes