page_title: Hawker Hurricane variants
section_title: Hurricane Mk II
hierarchical_section_title: Hawker Hurricane variants / British variants / Hurricane Mk II
caption_attribution_description: English: Description: HAWKER HURRICANE MKIIA at the en:National Museum of the Air Force
context_page_description: The Hawker Hurricane was a British single-seat fighter aircraft designed and predominantly built by Hawker Aircraft Ltd. Some versions were built in Canada by the Canada Car and Foundry Co Ltd
context_section_description: Media related to Hawker Hurricane Mark II at Wikimedia Commons
  The improved Merlin XX (Mk.20) engine appeared in 1940 featuring a new two-speed supercharger that could have its impeller speed changed by the pilot depending on the outside air pressure (altitude). At about 18,000 feet (5,500 m) (effective), it would be switched to a higher speed gearing ("FS ratio" – Full Supercharge) for added compression, while below that, at its lower speed gearing, ("MS ratio" – Moderate Supercharge), it "robbed" less power from the engine. The result was more power at both lower and higher altitudes, dramatically increasing the overall performance of the engine, peaking at 1,280 horsepower (950 kW). Because of the new engine the bay immediately in front of the cockpit was lengthened by 4 inches (100 mm). The carburettor air intake under the forward centre-section was redesigned and moved back 3 inches (76 mm). The more powerful engine was cooled by a 70% to 30% water glycol mix, rather than pure glycol used for earlier Merlin versions. This and the increased cooling requirements required a larger radiator and a redesigned, circular oil cooler housed in a deeper, slightly wider "bath".
caption: Hawker Hurricane IIA at the National Museum of the United States Air Force
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