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- Jul 2, 2007
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Maybe some recent test-pilot school graduate can help out on this one......
Whenever I do some so-called drag reduction mod on my fixed-pitch prop S-1, I test the results by flying a fixed altitude, fixed rpm, and seeing what speed I get (gps, two-way run). Often there is not too much speed gain at all, if any.
But a fixed pitch prop at a fixed rpm is only going to generate a theoretical resulting speed (pitch x rpm) minus some amount of "slippage" that increases with drag.
Take my 62" pitch prop at 2600 rpm. That's .000861 nm per rpm times 2600 rpm times 60, or 134.33 knots. What slippage? That's only about a knot more than I'm getting now.
Can the real gain only be measured by manifold pressure then? A draggy airplane turns 2600 rpm at full throttle and a slick one at 3/4 throttle? With the draggy one doing maybe 2 knots slower than the slick?
Yeah, its been raining for a while here and I'm going kind of buggy from not flying.
Edited by: Guido Lepore
