Doc1010

While it's no airliner, I am having an issue on a Cessna 421C that perhaps someone here would have some insight on.

Like normal light twin recips, the 421 before takeoff check list has a feathering check. The left prop, without issue, comes back with ease when the prop lever is brought to feather. Approaching 1000 RPM, I bring it back up, and it checks fine.

The right prop, however, I can place in the feather detente and the prop slows to approximately 1100 RPM and just sits there. If I run the check at a higher RPM, same issue.

My concern, of course, is whilst airborne and in the event of right engine inop, the prop won't feather. I suppose this could be caused by a low nitro-charge which I'm told should assist in the feathering action. For whatever reason, I can't seem to convince our maintenance department this could be an air-worthiness issue.

Thoughts, feelings, ideas?

9kBud

How well do the props stay synced in flight? I don't have any experience with the GTSIO engines, but when I have slow feathering coupled with props constantly in/out of sync with the TSIO's, many times it's a governor going bad. Definitely get it checked though, I've heard of props that were slow in the the feather check to take a couple minutes to stop during an in-flight shutdown.

dhc8fo

If it was my plane, I'd make them fix it. There is a reason you are checking parameters in a preflight.

I was giving dual in a 421 and we shut one down. When we went to restart it, following the POH and positioning the prop lever as instructed, it would not restart. Thankfully I had that rig issue brought to my attention in the past. We had to push the prop up to close to max before it unfeathered. The owner had it adjusted after that.

DirectTo

Had a 402 exhibit those same signs on the ground and it did turn into refusal to feather in the air. I don't know what MX did to fix it, but it got fixed before I flew it again.

9kBud

That's how I learned about it too!

wizepilot

I am surprised that owner would let you do an actual shutdown on a GTSIO. That could be an expensive proposition, especially if the engine was on the very hot side, which they usually are. I had an owner once tell me to not even think of shutting one down on a training flight, or he would break my arm.

Ewfflyer

If you are training, you shouldn't be leaned out too much or running high power. I would suspect you could have some decent numbers if you keep it below 25" for a few minutes before you pull one. The key is gradual, not total change.

I agree you shouldn't do one if you dont need to, but I wouldn't mind doing one on the bird i fly once it gets the next overhaul. Right now it's within 50 hrs, I would be afraid of that doing something wonky until then. Maybe the last flight before it's done I should!

wizepilot

Uh, yeah, I agree on the gradual change. The man I learned the most about 421's from is my boss, who has about 20K hours in them. He knows more about them than anyone both mechanically and financially. And, I have been flying them on and off for at least the last 30 years.