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Old 02-12-2014, 06:55 PM
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iron eagel
 
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Originally Posted by airraptor
iron Eagle not to pick on you but those pitch speed calulators are not that accurate at all for our model planes. I have ran a few planes on GPS and pitot tube sensors and they showed a higher speed than what the pitch speed calc reported.

The propblem is that the just base it off the pitch alone. they dont account for the airfoil and the difffent pitchs of the props out there. Some of these also showed less than the pitch speed also.

My 12,000 as above is also the ground speed i will expect some unloading.

Either way I will try to see what i can come up with.
I agree there good for indication only, what you actually get will be different. FWIW I have a chart which just uses rpm and pitch not taking diameter into account which has a 15 pitch prop at 12000 rpm having a prop pitch speed of 200 mph. When you get to the point where the prop unloads your RPM will climb, even 1K rpm will give you about 8-10 mph more speed.
There have been many cases were a good clean plane outran the prop pitch speed by considerable amounts.