Quote:
Originally Posted by Crumpp
Sure you have some thrust being produced but it is not EXCESS thrust. It is excess thrust that accelerates the airplane.
In a dive from Vmax, the only excess thrust is the component of weight.
Propeller thrust only accelerates the aircraft within its envelope.
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Crumpp,
I totally disagree with you. Imagine that you are now flying a la7 with 110% throttle and you get Vmax speed. The efficiency of propeller is 80%, yes, you propeller are producing thrust(not big) which is equal to La7's drag force. Namely, La7 is in equilibrium. You have no excess propeller thrust, right? Till now, we should have no bifurcation.
And then you suddenly turn off your engine and feather your propeller, It's obvoius that you are about to lose speed because your engine is dead, but you push the stick forwards and begin to dive. A portion of gravity will help you counteract the dargforce and make you maintain Vmax during your "dead enigine" dive. If you dive in a more steep angle, you could even faster than Vmax. in another word,
you are spending altitude to maintain your Vmax or get even more speed.
During your "dead enigine" dive, if you suddenly turn on your 1850HP engine, will you dive faster? Will engine give you
excess thrust?
In my opinion, definitely, you will get greater dive acceleration because your propeller efficiency is 80-60%.
In your opinion, prropeller efficiency suddenly become zero from 80% when aircraft speed is somehow higher than Vmax.
Quote:
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Propeller thrust only accelerates the aircraft within its envelope.
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Propeller thrust could accelerate the aircraft beyond its envelope, as long as gravity force comes to help aircraft-----DIVE.