ORIGINAL: davidej
da Rock
Thanks for your comments.
The djaerotech article is very interestion altho I would classify it more as assertions than scientific proof. It considers a number of possibilities none of which are exactly the question I have posed. However the general trend of it seem to support my case.
He argues mainly about energy and where it goes. It seems to me that, if you keep your engine running, you must generate some power, so where does it go if not in a faster glide.
However, I have put my exact question to them and eagerly await the answer.
david
If the engine is running at such a speed that the prop's advance is much less than the plane's speed in the glide or dive then the prop is "flying" at a very negative angle of attack and lift is actually being generated towards the tail rather than to the front. At the same time the prop is trying to autorotate thanks to the pitch and that is speeding up the engine to where it's "coasting" at a higher RPM than the idle mixture would provide so you have engine drag slowing down the prop so it can't freewheel up to speed.
Think of the spinning prop as a terribly inefficient gyrocopter rotor that happens to be sitting in the wrong place and lifting the wrong way.