Rockwell Turbo Commander

[low-n-slow]

In theory (and theory only) you can hold onto the propeller of a PT6 powered engine and start the engine; the engine isn't driving the propeller. The only force acting to turn the propeller is exhaust gas from the engine. The problem with that theory is the amount of torque imparted to the propeller turbine wheel by those gasses; you'll get tossed and hurt if you try to hold onto the propeller.

Avbug, last time I had my airplane in the shop for a HSI (PT6) and related work and as I was speaking with the mechanic we got on this very same subject. He told me of a P&W rep that visited their shop (Southeastern) actually demonstrated holding onto the prop untill the -34 reached 52% (ground idle on my plane) and then let go. I wouldn't have believed this but I know the mechanic very well and don't think he would have BS'ed me.

 

[avbug]

I've heard of the same demo. I've never seen it.

On the turbine drom we have a -45R. To secure it overnight, an eyebolt is installed under the spinner and just aft of the spinner. a collar made of thick webbing with a clip goes around the prop, and clips to the eyebolt.

An individual (not me, I swear) attempted a start a few years ago with the "dog collar" attached to the prop. It bent the eyebolt severely, broke the clip, and tore the webbing...something like two thousand pound test webbing. The prop still turned.

I've been tossed aside doing differential compression tests before on large engines with big props. Even with 80 pounds of air or less in the cylinder, and only one one, the prop can have some push to it once the cylinder comes off TDC.

Even at low idle, the PT6 still has enough torque to move you.