Dick,

The question doesn’t make sense. Twisting force isn’t a force at all, but a torque. A torque is the product of a force acting at a moment arm. For a given torque, the force can be any value depending on the moment arm, whereas the propulsive force is simply a force.

Your statement that, “…any conversion from device to device or mechanical ratio or change of direction etc., has a resultant loss of some kind -NEVER a gain .” is an attempt to state the law of conservation of energy but is not completely accurate. Using a simple lever it is quite possible to gain a large force output from a small force input.

Applying energy conservation to the situation described in your question:

work input to the propeller (by the engine) = work done by the propeller (in moving the air) – loss

The work input would be the torque applied to the propeller times the RPM.

The work done by the propeller would be the mass of air affected by the propeller, times the change in velocity across the area of the propeller per unit of time.

While it is obvious that work in must equal work out minus loss, for airplanes of conventional proportions, the force required to produce the torque to turn the propeller is much less than the thrust force produced by the propeller.