On my O-2, I feathered each engine in flight (one at a time) and performed a complete shutdown, ie, mixture to idle cut off, mag switches off,etc. When the front was shut down, I hand pumped the gear down to make sure that everything worked as planned under a controlled condition, before it was an emergency condition. I then unfeathered each engine and did an air restart, no problems. The O-2's have unfeathering accumulators, so that made things go a bit faster.

I'm not sure what damage you can do to an engine by feathering the props fully, in a normally aspirated engine? The only thing that I can possibly see is that it puts additional stress on the starter and starter adapter because of the aerodynamic load.

I've been bending wrenches on airplanes since 1975 for a living, and there are a lot of wives tales, half truths and superstitions among all types of A&P's/IA's. When I see something from a manufacturer that says its OK to do, or directed to do, as in a checklist, there has been some discussion from the engineers that this is an approved proceedure.

The internal feather latches on the prop blades are inhibited below approx 1000 rpm so its not necessary to go below 1200 rpm to check for feather and I think that the governor won't govern below 1500/1600 rpm unless the pilot spool/control arm is out of rig. The latches keep the blades from going to feather below 1000 revs, as a normal shutdown. I had a prop that would go to feather during a normal shutdown, and the latches were sticking retracted, allowing the blades to go to feather due to spring tension.

Cycling the prop only once will not purge the cold oil out of the dome, but it may puge any air that may have accumulated there during a shutdown period. It doesn't take a large volume of oil to change the pitch.

What everything boils down to is that TCM is going to have to issue a service bulletin that says feathering a prop will damage an engine before I beleive whats being tossed about.

Thread resurrection!

Considering purchasing an O2, and determined that it had the wrong governors installed so un-feathering is not possible (no unfeathering port on the installed governors) and possibly the unfeathering controls were disconnected. Anyone have any experience with this? or recommendations?

If we do indeed purchase and have the correct governors installed (and assumedly the unfeathering controls), what is the best way to check that it all works - complete feather and unfeather cycle? @Paul462- it seems to work fine in the air, ever accomplish it on the ground with similar results? Thanks!

I was checking out a new pilot in my plane the other day and the pilot fully feathered the rear prop during the feather check. The engine kept running (slowly.) We were able to get it back into normal ops without shutting down.

02s had unfeathering accumulators, and different governors. Perhaps yours had the accumulators removed, but still has the old givernors? Or if in place, the accumulators need a good nitrogen charge, about 90psi IIRC.

Could be... We have it in overhaul at the moment and the mechanic tells us it has the wrong governors (both props). We'll have to actually dig into the airplane to see if the connection is still there (to actuate the accumulators - not sure how it is mechanized), we obviously want to get the correct governors installed and would like the ability to unfeather it if it is every needed.

Feather/unfeather on the ground seems to be some debate weather that causes undue stress of the aircraft (perhaps that is more of an issue WITHOUT accumulators to help with the unfeathering?) Thanks!

JMH, there are two correct accumulators for sale on Ebay right now. You could buy both of them for under $400. Not a bad deal if that's the direction you decide to go.

Thanks! Good idea...

We went ahead and bought the maintenance manual for the O2 and it actually has a operational checkout procedure for feathering/accumulator - the key piece is to to go to idle-cutoff and kill the Mags when the rpm starts dropping... and then leave it undisturbed for 6-8 minutes. Then move the prop lever to full increase and observe blade angle change.

More research to do.

Not gonna have any blade angle change from a non-running motor UNLESS you have accumulators. You can always unfeather props on the ground with a wooden "prop blade wrench".