Supermarine Spitfire variant
Supermarine Spitfire Mk II
The Merlin XII version, rated at 1,175 hp, with Coffman cartridge starting and a wide-bladed Rotol propeller. It was the first Spitfire built exclusively at the huge Castle Bromwich shadow factory and replaced the Mk I in front-line squadrons by the spring of 1941. 921 were built.
- 921
- Units built
History
The Merlin XII and the shadow factory
An early Mk I, K9788, was fitted with the new Merlin XII in the summer of 1939, and the trial went well enough to justify a whole new mark around it. Two features set the Mk II apart: the 1,175 hp engine itself, cooled by a 70/30 water-glycol mixture rather than the neat glycol of earlier Merlins, and a Coffman cartridge starter that freed the aircraft from the trolley accumulator batteries wheeled around RAF airfields. The cartridge system required a small teardrop blister on the starboard cowling, one of the easiest ways to recognise the mark.
Built at Castle Bromwich
The Mk II was the first Spitfire produced solely by Lord Nuffield's vast shadow factory at Castle Bromwich, the plant that finally broke the industrial bottleneck which had held back the Mk I. A wide-bladed Rotol propeller of 3.27 m diameter, identifiable by its larger and more rounded spinner, became standard at the same time. The new engine and propeller were worth about 6 to 7 mph over a late Mk I below 17,000 ft and improved the climb; accumulated weight kept the top speed below that of the earliest Mk Is, but as a fighting aeroplane it was distinctly better.
Sub-variants and service
Like its predecessor the mark came as an eight-gun IIa and a cannon-armed IIb. Deliveries were rapid enough that the RAF had re-equipped its front line by April 1941, displaced Mk Is going to training units. Early in 1941 a small batch became "long range" Spitfires with a fixed 40 gal tank under the port wing; with the tank full, manoeuvrability, speed and ceiling all fell away noticeably, but several squadrons used them for bomber escort. Once out of the front line, fifty aircraft were converted for air-sea rescue as the ASR Mk II, with a Merlin XX, a rescue pack in the flare chute and smoke markers under the port wing.
Assessment
All 921 Mk IIs came from Castle Bromwich, and some were later converted to Mk V standard. The mark has a less glamorous reputation than the Mk I or the Mk IX, but it was the version that proved the Spitfire could genuinely be mass-produced — precisely what the RAF needed in 1941.
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