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Originally Posted by Talisman
High Banks,
Just to clarify, are you suggesting that the RAF introduced a new MkII version of the Spitfire in the middle of the battle that did not have emergency operational power for combat and thus was slower in combat than the Spit MkI with operational emergency boost engaged?
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So, if the Spit MkI is 6 to 7 mph slower at heights less than 17,000 ft, then to my mind the data indicates that the level speed of the Spit MkI at 1,000 ft was 287 mph ( Spit II, 294 mph at 1,000 ft minus 7 = 287). If the Spit I pilot then engages operational emergency boost, he then gets an extra 25 to 30 mph, giving a speed of 312 mph (287 + 25) at 1,000 feet on 100 Octane fuel.
So, with the Spit MkI at 312 mph on emergency boost at 1,000 feet and the Spit Mk II at 294 mph without emergency boost, it is slower in combat than the Spit MkI unless the Spit MkII has emergency boost available. Or am I missing something?
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Yes that's my conclusion from the available data.
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Surely the Spit MkII had emergencey power operational boost available to provide and extra 25 to 30 mph for operational emergency, just like the Spit MkI.
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Definitely it was physically available and the amended pages confirm it. However we don't know since when the pilots where authorized to use the emergency boost with a Merlin XII. The pages from the Pilot's Notes Spitfire II from the 1940 time-frame that I've seen so far do not authorize the use.
I would be glad if someone could provide a proof since when +12 boost was authorized for emergency conditions and not only take-off.
In addition we don't know what happened if the pilot used the +12 take-off boost for example during combat (engine damage, no boost increase, nothing ... we don't know).
Compare it with the Hurricane II with Merlin XX which was introduces at about the same time (August-September 1490) and had +12 take-off boost authorized since introduction and emergency boost was approved shortly later in November 1940.