Yes.


No pics handy, but the roll and yaw trim systems have long shafts to the back of the console which change length depending on what is installed

See item 16 below:

My console was shortened as much as it can be. Makes a HUGE difference in cockpit comfort! I can basically walk into the pilot's seat now.

Mike C.

Not effectively.

On the PT6, the prop only has the last turbine wheel attached. That hardly moves any air at hand prop speeds. The gas generator section isn't turning.

On the TPE331, the entire rotating group, 3 turbine wheels and 2 centrifugal compressors, turn with the prop. It moves quite a lot of air.

The main benefit of being able to move air post shutdown is to get any residual unburned fuel off the nozzles. If the fuel stays on the nozzle and gets hot without burning, it turns into carbon deposits which lead to streaking fuel nozzle patterns. That leads to less atomization of the fuel and longer flame lengths that damage the turbine wheel and stator.

Using the starter on PT6 shutdown does basically the same thing as the hand prop on a TPE331, turns the main part of the engine to get airflow. This both evaporates unburned fuel and also cools the engine. Spinning the prop really won't do that very well.

Mike C.

The EPA requirement is that you can't just dump it on the ground which was what the PT6A used to do. Now they catch it in a container and burn it on startup in the exhaust.

Not sure on the 441, but in the TPE-331 installation in the Mits, the EPA can collects air pressure once the engine speed gets up above around 96%. It stays pressurized for the rest of the flight. When the RCS switches are pulled back when shutting down, the air pressure is pushed through the fuel lines and the engine temps momentarily jump at the fuel is burned off in the engine, then it spools down to stop. But as Mike suggested, a droplet of jet fuel may well still sit at the ends of the nozzles and that's one of the main reasons the props are turned a little while after shutdown. Supposedly it can also prevent shaft-bow...but I'm not even sure that really happens (or if it does, it must be pretty rare as I've never seen, felt or heard anything odd in a hot engine).
I understand that the single turbine wheel connected to the gearbox in a Pratt will move some air (and I'll be the first to admit that I don't know nearly as much about our King Airs as my Mits), but wouldn't the final turbine wheel actually just suck a little air into the exhaust ports rather than pulling a large volume of flow through the intake of the power section? I guess some of that airflow would make it to the combustor, but I'd be surprised if it does much. Should be easy to test though. Shut down, get the baggage and pax out and let it sit for a few minutes, then check the indicated ITT drop over about 3 minutes, pull the prop through 20 blades and check again at 3 min to see the delta in temp drop. Fun experiment.

If the prop is turned in the normal direction, the turbine wheel will tend to move air out the exhaust.

But it won't do a good job because the turbine blade shape is designed to slow down fast air turning it into torque. Thus the turbine blade shapes are facing the wrong way. Thus the lift it gets is poor, which yields little air movement.

In this photo, the air moves left to right through the turbine disk which spins clockwise:

If the disk is spun clockwise, the airfoil shapes of the blades will do a very poor job of moving air. It is like a highly cambered wing flying upside down. They are basically backwards from what would work.

In contrast, the compressor section of the engine, be it axial or centrifugal, has the blades in the right shape to move air. Alas, in the PT6 you can't spin the compressor section from the prop, you can only spin it with the starter.

One of the reasons the TPE331 has a much longer overhaul interval than the PT6 is the ability to keep the nozzles clean with the manual prop spin.

Mike C.

Yes...my mistake. I was forgetting that the PT-6 and 331 have the exhaust reversed (so to speak) I was thinking of the turbine wheel attached to the propeller trying to pull air through the compressor section (which I erroneously thought of as leading to the exhaust behind it but the airflow is reversed). Anyway, what I was thinking is that the seals in the non-moving compressor section must be pretty tight with respect to limiting airflow drawn forward by the hand-spun power turbine wheel.

It’s the same in the 441, except it’s a button and you hold it down to release the air. What is RCS?

RCS= Run, Crank, Stop toggle on quadrant. Three position guarded toggle that sits forward for start and run (ignitors armed), mid for just crank (like when motoring turbine), and spring loaded aft (firing, EPA can and closing fuel valve to shut down engines). One toggle for each engine.