Can a propeller stop turning during a flight?

Question

My partner is convinced that during scheduleds flight on a propeller driven aircraft, the propeller routinely stops turning during the flight, i.e. it is stationary. I say they may be feathered, i.e. turning at wind driven speed or that they appear stationary due to stroboscopic effects. Surely the propeller is directly driven and therefore to 'stop the prop' you would have to stop the engine, surely this is not something you would do by choice on a flight. Thank you

Answer 1

Yes they can stop when feathered.  But routinely, No!  Our eyes register vision in frames.  Digital not Analog.  If your friend routinely sees the propeller stop it's probably because his eye sync is on the same frequency as the propeller RPM.  You can see the same phenomena in old westerns when the wagon wheel stops and starts to turn backwards.

Answer 2

During flights, with engines operating normally, the propellers are never stopped (routinely or otherwise). A propeller may, however, be stopped if the engine is shut down and the propeller is feathered.

Answer 3

>>  Can a propeller stop turning during a flight?

They only stop if the pilot shuts down the engine - and is going slow.  TWO very dangerous moves.

A pilot would NEVER shut off the engine in flight (unless there's an emergency - like an engine fire).

===

>>  propeller routinely stops turning during the flight, i.e. it is stationary.

Crazy... Just crazy thinking.

Good Luck...

Answer 4

Yes a propeller can stop during flight - it is usually associated with the engine being shut off or experiencing some type of failure causeing the power to the propeller to stop.  

On variable pitch (where the pilot has control of the pitch of the blade in flight) the propeller will often in the case of being shut off be placed in a flat pitch mode helping to reduce the drag the propeller against the wind.

Also some model propellers like those on Turbo Prop (aka Prop jet aircraft) the propeller can be placed into reverse pitch or Beta pitch.  This can be used as a braking aid.

On McCauley Propellers website there is a good description on various propellers.  (the link is below)

Answer 5

Engines are not normally shut down during a flight, so the props are always turning.

Even if an engine were shut down, the prop might still windmill, unless it is completely feathered.  In some turboprops, the propeller is not directly connected to the turbine engine, so it can windmill freely when the engine is not running, although feathering it helps to prevent this.  Piston engines are more likely to stop the prop completely when the engine stops, as the connection is direct.

But, as you observe, engines are not stopped in normal flight, so most of this discussion is moot.