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1941 advertisment for Rotol constant-speed propellers, by the standards of the era referred to as “airscrew”. The introduction of the Rotol 3-blade constant speed propeller which began in June 1940 finally released the full potential of the Spitfire in terms of performance. It added about 7,000 feet to the flight ceiling, cut time to altitude by around 1/4 and improved diving and turning performance. It also cut take-off distance by 1/3 and made the airplane simpler to handle at low speeds.
The improved Spitfire Mk. II, factory-equipped with Rotol propellers and introduced into combat service on 16th August, 1940, was also fitted with a Rolls-Royce Merlin XII which delivered about 190 hp more power. This further increased the climbing speed and service ceiling. The Spitfire II was some 6-10 mph faster than the service Mk Is below 17,000 feet but some 4-8 mph slower above 23,000 feet.
[Jenny Scott coll.]