Originally Posted by
HuggyU2
I understand what you're stating. I've also read some places where they show/believe the difference is negligible... and in some cases, opposite of what you say, depending on prop length and chord.
Again, I don't know the answer. But I'm hoping someone knows of a link to a solid source.
Many flying Vans RV's have looked at this question since the aircraft has such a poor glide ratio. Quite a few have actually shut the motor off and ran tests. The aircraft glides far better with the prop stopped then windmilling. Probably on the order of 20 to 25%. This is a fairly small aircraft often with a big prop. If the prop is composite it's fairly easy to get it stopped. If it's metal it can be more difficult since there is no ability to feather. Course verses fine pitch also makes a difference but not nearly the effect stopping the prop has.