P39 performance per included test dated October 1941 (1 Viewer)

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Part of the problem may be what limits were being used during the tests?

Leaving out WEP and over boosting, standard American procedure for testing climb performance called for using Military power ( for the Allison of the time, 3000rpm/44in 7lbboost) for the first 5 minutes of the climb and then throttling back to max continuous power for the remainder of the climb.

The British pilots notes would call for the entire climb to be done at a climb rating or 30 minute rating of either 2850rpm or 2650rpm and 6 1/4 to 9lbs boost depending on model of Merlin and when the boost limits where changed.

Without knowing what models of the British planes were used and what boost limits were used on the engines the comparison, while interesting, doesn't really prove much one way or the other.

Please note the the American " max continuous" is not the same as the British "max continuous" as the American rating was not 30 minutes but either 1 hour or time unlimited ( until the fuel ran out).
 

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