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If a jet engine is shut down in flight, it continues to turn due to the aircraft’s forward motion forcing air through the engine, causing it to “windmill” in the airflow.

Is this also true for turboprops? When a turboprop engine is shut down and its propeller feathered, do its compressor and turbine rotors keep windmilling in the aircraft’s slipstream, or do turboprops have some way of closing off their engine intakes to prevent this when the engine is shut down?

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    $\begingroup$ An interesting fact is, a lot of turboprops are mounted reverse, e.g. exhaust facing front ("front" meaning the side of the output shaft, which is why a lot of turboprops have exhaust port on the front and bottom). This makes windmilling the core quite counter-intuitive (not saying it's impossible). $\endgroup$ – user3528438 Apr 11 at 4:11
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A feathered propeller is designed not to windmill in flight, however in the case of a power turbine or even a propeller connected to both the compressor and turbine, it's far easier to turn than an old radial when in the feathered position.

Nothing physically stops the propeller from turning when feathered beyond the force required to turn the power turbine/gearing or whatever the propeller is connected to and the air hitting it at the right angle. Straight airflow shouldn't turn it, however any flow from the sides would turn a feathered turboprop. Unlike a turbofan, the propeller changes pitch so the air affects it differently.

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There is no any closing. Why do you want to prevent windmilling in a turbo prop? Turbo props are free power turbines. Compressor is not connected with propeller so it can windmill.

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    $\begingroup$ Except for the TPE-331 and others. $\endgroup$ – acpilot Feb 1 at 0:41
  • $\begingroup$ T56 is single spool $\endgroup$ – MikeY Apr 11 at 0:47

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