PA32R Prop Governor

[aewanabe]

On the pre-class written test regarding the PA32 systems, we are asked about the prop governor. If you lose oil pressure, will it go to high/low RPM, what about high/low pitch. I'm going crazy with the AFM trying to find anything that says, nothing in Sections 1, 7, 8 or 9.

1) anywhere else I should be looking for this answer?

2) In absence of any evidence to the contrary, I'm assuming it works like the governor on all other complex singles that I've flown. IE the spring/nitro charge drives the prop toward the low pitch/high RPM stop, and oil pressure moves it towards the high pitch/low RPM stop; therefore loss of oil=high RPM/low pitch.

Can anyone confirm/deny this? Thanks.
Scott

 

[Blueridge]

You answered your own question in #2. The easiest way to think about what happens to the prop with no oil pressure is to look at it when the plane is sitting idle on the ramp. Without the engine running, there's no oil pressure to get into the hub and therefore the prop goes into flat pitch / high RPM. Note that this is only true for piston powered engines. The props on turboprops go into feather without oil pressure as seen in King Airs, Saabs, Brasilias, etc.

You would probably have to look into the maintenance manual for a diagram of the prop on your airplane as I'm almost postive that there's nothing in the POH about it. (I flew the Cherokee Six and I don't remember anything in its POH about it.)

Hope this helps a little,

BR

 

[Dan CFI/CFII]

The difference in which way it goes is not piston vs. turbine--

it'll mostly be single vs. twin (with the exception of some turboprop singles). In the twin, you're gonna feather that prop if the engine dies right? So, the loss of oil pressure just starts that process of going to high pitch already.

But in the Lance, it'll go to low pitch, and the suggestion about just looking at it on the ground is a good one, you'll see it with the lowest oil pressure it can possibly have!

Dan

 

[FlyinBrian]

It's true that most twins are designed to move toward feather in the event of an oil pressure loss. The fact that singles will go to low pitch/high RPM when they shut down does indicate that their design is opposite that of most twins.

In case you're wondering why you don't see piston twins go to feather when they are shut down, they usually have a lockout pin system that will lock the blades in place when the engine gets below a certain RPM. Without this feature, you'd be starting engines from feather which can be difficult and hard on the engine.

Free turbines can be started in feather and run in feather without any undue strain on the engine.