Free spinning Turbine
 

I was wondering if anyone could tell me exactly how a free spinning turbine works? In particular the PW150A.

Its my understanding that in a free spinning turbine setup the prop is not directly connected to the LP or HP compressors, but rather it is only connected to the power turbine which is located aft of the LP and HP turbines.

Therefore If I were to spin the prop on a free spinning turbine system, would the only component to be moving in the engine be the power turbine and associated shaft?

In addition to what has already been said, both turbines (gas generators and power turbine or low and high pressure) are "linked" only aerodynamically; the gasses exiting the gas generator or NL or low pressure turbine (I think those are the names) move the power turbine and in some engines, such as the PT6A, both turbines move in opposite direction: one clockwise and the other one anti-clockwise.

Free-turbine engines are quite common in helos, meaning the power turbine can maintain constant rotorhead rpm while the gas generator speed can adjust up or down to match power demand.

also in aircraft the mostly typees are a free turbine. an example of a not free turbine ( singeshaft turbine) is the TPE331.

the pt6a is a reverse flow design where the free power trubine sits in the front and the compressor stages as well the compressor turbine in the back.

best regards

...except when employed as a pusher, in which case it's turned around the right way... :)