Quote:
Originally Posted by JtD
Regarding level speed performance of the 109, a question raised by I think MiG-3U puzzled me, maybe you have a good explanation, I'm at a loss for now: How come the 109E is faster than the 109F at less power, if you accept the 498 km/h for the 109E at 990ish hp from the V15 test and the 495 km/h for the 109F at 1065ish hp from the 109F Kennblatt?
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Its difficult to say how much it is on the 109F Kennblatt because the Kennblatt's figures are with the original ratings of the 601N at 495/515 (1.42/1.3, which were reduced to 1.25). In short the 495ish figure is for 1.3ata.
My best guess is that there was a major difference between the Emil and Friedrich propellers (also according to the propeller effiency curves I have seen), the latter was of smaller diameter and almost certainly meant for high altitudes, and probably less efficient in denser air, hence the relative stagnation of speed near SL. The Friedrich would be probably faster with a different prop.
But all of this is not so extraordinary or a surprise since the same can be noted when it comes to the Mark I / Mark V / Mark IX Spitfires's evolution. Hell the Mark I. at +12 is supposedly faster at SL than the Mark IX at +15 boost, how come..?