TurboProp Engine
 

On a Turboprop engine if you spin the prop will the engine turn? and if so, why?

Ian

Depends on the type

A Garrette has a direct shaft running right the way through from the back of the gear box to Compressor, to the turbine So when you turn it the whole lot goes round including hydralic pumps the works

A PT6 on the other hand is a free turbine so it won't

An example of a free turbine aircraft is the ATR which when they lock the propellor stationary they can use the engine as an APU.

A striaght Shaft engine example would be a Jetstream 31/32/41.

There are effeciency benefits of having a direct shaft engine but they harder work to start because of having to spin the prop up as well and they take a bit more looking after to manage because its quite easy to max them out on egt if your not careful.

On a free turbine engine, PT6 and the like, the prop will rotate the prop reduction gearbox and N2 or power turbine gear trains and ancillaries.

This occurs due to the inherent characteristics of a free turbine engine, that is the power turbine and gas producer turbines are not coupled.

Mad-jock has explained fixed turbine eloquently enough.

Cheers
BH

The prop has to rotate the engine to do and air start should you have to

http://www.trainingcrue.com/v/vspfil...6_A0_GEN-2.jpg

http://www.seattleturbine.com/2300022701_2-04.jpg

I hope you can see in the first pic of the PT6 the front half isn't connected to the back.

Not a very good picture for the TPE331 but i think you can see the radial compressors into the combustion cans then out into the turbines there is a straight shaft right the way through

Thanks everyone for your help! mad_jock really well explained thanks!

Ian