[Steely Tom]

It's mechanical linkage from the throttles quadrant, no relays, and it works off of oil pressure flowing thru the mechanically linked valves.

Thanks for the info, blackdog. I concluded that prop-pitch was controlled by electric actuators because I've seen so many "prop pitch motors" for sale in surplus catalogs. Obviously, just because some props are controlled by electric motors doesn't mean they all are.

I guess the mechanical linkage makes me feel a little better, because it can't go into a failure state just due to some little piece of dirt or whatever. Still, hydraulic valves can fail...

Well, I guess there are a lot of things on an airplane that will kill you if they fail. Prop-pitch control is just one item on the list.

(steely)

[blackdog]

I'm not certain, but I think there are a few piston planes out there with reversing pitch control. I think the Queen-Air may be one. I know that when you get a prop stuck in feathered position in a Cesna 402, that it is impossible to start the engine on the ground.

I wonder what the pitch control is on helicopters? I see linkage rods that come up to the rotors, but I'm not sure what device moves them up and down. I was told a story once in flight school, which of course means it could be as false as true, but that a Ranger pilot lost pitch control and reached up thru the interior panels and manually operated the linkage by hand. He could only select full deflections though.