[RedDevil]

Originally Posted by aerohead

1) In # 37 ( permalink ), some other dave states that it is the 'triangular
sails- propeller blades' that are responsible for Blackbird's motion.
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2) The wheels cannot power the propeller if the propeller is the sole source of power for the wheels.
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3) If you examine turbine blades and propeller blades, you may find that their airfoil geometries are 'reversed.'
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4) In a bonafide powerplant failure during flight, in a variable-pitch propeller aircraft, the aircraft checklist instructs the pilot to 'de-pitch' the prop, in order
to reduce prop-drag, thereby increasing glide radius for a dead-stick landing.
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5) The 'Blackbird' propeller analogy implies that, in a flight emergency, the pilot would merely 'reverse' the propeller ( like a Lockheed C-130 Hercules ), and the free-wheeling reversed propeller would now be capable of maintaining enough thrust for level flight.
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6) The 'masts' which hold the aircraft propeller are free to move in relation to the aircraft fuselage.

None of this addresses what was in the post you replied to.
But I'll reply to yours point for point. The first two hit the essence.

... it is the 'triangular sails- propeller blades' that are responsible for Blackbird's motion.

Yes, but you have to understand in what way they are responsible.

The car is moving faster than the wind, but as the propeller spins backwards the surface of the blades is moving slower than the wind.
So the wind pushes against the blades, forcing the car forward.
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2) The wheels cannot power the propeller if the propeller is the sole source of power for the wheels.

The forward vector of the force on the blades powers the car forward, the sideways vector works against the gears that push the propeller against the wind. If the gearing is set so that the surface of the blades still moves forward, albeit slower than the car and of course slower than the wind, the force fighting the rotation is less than the forward pull on the blades.

The forces would be equal if the propeller would force the air backwards at the same speed as the car is moving.
The optimal setting is just slightly less than that; the friction in the system determines how much less it needs to be to function.
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3) If you examine turbine blades and propeller blades, you may find that their airfoil geometries are 'reversed.'

This is not a turbine. The propeller does not harvest energy through rotation, but through forward pull.
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4) In a bonafide powerplant failure during flight, in a variable-pitch propeller aircraft, the aircraft checklist instructs the pilot to 'de-pitch' the prop, in order
to reduce prop-drag, thereby increasing glide radius for a dead-stick landing.

A powerless plane has no surface that moves with a different speed to the wind to do anything with, what renders their propellers useless. Putting them in vane position is the only sensible thing to do in that scenario.
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5) The 'Blackbird' propeller analogy implies that, in a flight emergency, the pilot would merely 'reverse' the propeller ( like a Lockheed C-130 Hercules ), and the free-wheeling reversed propeller would now be capable of maintaining enough thrust for level flight.

Second flight analogy, but again if you have no fixed surface moving at a different speed than the wind you have no source of power.
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6) The 'masts' which hold the aircraft propeller are free to move in relation to the aircraft fuselage.

Third flight analogy. It is a flight away from the core mechanism at work.