Prop control all or nothing

YankeeClipper · #1 08-19-22, 08:48 PM

My IA was putting the final touches (or so he thought) on my first annual. When we spoke last week he noted that the rear governor might need to be sent out, as the prop control would do nothing until pulled back about 1/3, at which point it seemed to go pretty much to feather (or at least it would nearly stall the engine from an initial 2k rpm). Governor failure made enough sense to me, but I still wanted to do a few run ups for the first time in about a year (and since I got my front engine IRAN’ed recently at Zephyr).

I jump in today, unfortunately to find quite a number of things out of sorts. Back pressure on left brake, hard starts both hot and cold, on both engines (and the front has a brand new iFly!), and a few other things. Anyway, sure enough pulling back on the prop control does nothing to rpm until about 1/3 to 1/2 back, at which point it drops all the way to near stalling. Alright … he warned me, and it’s a pretty old overhaul. Then I try the front engine: same thing!

Now what are the odds that both the front (right after an IRAN—though I don’t know if they touched the governor) AND the rear both failed the same way at the same time? When I flew this from VA to CT in ‘20, it both props behaved as expected. It has virtually no hours since that flight. Also, have any of you experienced this all-or-nothing behavior on prop adjustment?

Thanks,

Gray.

Kim Geyer · #2 08-21-22, 02:42 AM

I’m thinking your prop governors are fine. They only govern at higher rpm.

mshac · #3 08-21-22, 06:54 PM

I think Kim is right. When you do a run-up check at 1700-2000 rpm, all you're doing is making sure the props will feather.

Do your governor check again at full take off power (on one engine at a time) and see if the results aren't different.

YankeeClipper · #4 08-22-22, 08:25 AM

I will definitely try that. Surprised my IA doesn't know this though (even if he isn't a pilot).

cjordan · #5 08-22-22, 11:24 PM

Not sure about what you have going on. I usually run to 1800, check mags then push to around 2000 to cycle.( Never see anything near stall here, maybe 500rpm drop or so) Next pull back to 1500 and take it all the way to feather check, pulling all the way back with the (to the right and back to the stop on prop control procedure) That pulls the motors way down as you describe. Don’t see this on initial though run up though.

Sounds like governor (or linkage) issue if you aren’t deliberately going to feather on initial run up.