Thrust from a propeller drops as speed increases to a theoretical zero. When this happens, what is providing the thrust to overcome drag? The forward momentum of the aircraft?

Think of it this way - the propeller is attempting to smoothly slice its
way through the air, but the air gets in the way. If the propeller
blades were in completely flat pitch, it could do so standing still (in
zero wind), but would provide no thrust (I'm leaving out the fine points
of the airfoil, not important to this view).

If there's a wind on the nose however, this superflat pitch propeller
would not slice through the air; you'd have to change the pitch to let
that air slide through the prop as it's turning. The stronger the wind
on the nose, the more you have to unflatten the pitch. Don't do it
enough, and the plane will be blown backwards by the wind. Do it too
much and the plane will move forward due to thrust.

The same thing happens in the air, except that since we depend on the
prop to pull the plane, we never get to "super-flat" pitch. And in a
dive, I suppose you could get the plane to go faster than the propeller
wants to drag it, but gravity is helping in that case.

Jose
--
He who laughs, lasts.
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