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MT P860-3 Prop Gov fail.
This is a new thread branch off of my original AOG thread relating to news and questions concerning the MT prop gov issue.
Original thread here. http://www.vansairforce.com/communit...d.php?t=140840 |
>>If somehow you didn't overspeed your engine/prop you got very lucky. The other recent (identical?) failure wasn't so fortunate:
http://www.vansairforce.com/communit...ight=overspeed Might be worth a look at engine monitor data, if you have a record.<< Thanks for that link. I hadn't seen that and the pix look almost exactly like mine. The only difference is that there must be two pressure chambers in the unit to maintain pitch because my failure caused the RPM to drop rather than overspeed. I was about 18-19 on the RPM at full throttle and 800 on idle descent. Aside from everything else, the landing was much different due to lack of drag. First time I ever slipped the airplane to be honest to get the sucker down as a go-around would have been a nightmare. A short field would have been dicey. Good things to think about and practice on a routine basis. |
Myron,
Have you opened the governor to see what came apart inside? |
I'm confused about something, perhaps somebody can clarify.
As I understand it, single engine airplanes with constant speed props are set up to go to fine pitch, not coarse, upon loss or reduction of governor oil pressure - so that you can still make power. Twin engine airplanes with constant speed props are set up to go to coarse pitch (feather) upon loss of governor oil pressure - so that you minimize drag on the side with the failed engine. Yet this incident seems to indicate that an RV-10 (single engine) went to coarse pitch, with 500 RPM lower than expected upon governor failure, which seems strange. This seems to be a different failure mode than the Todd Stovall RV-10 failure from another thread [or at least different symptoms - coarse pitch (lower RPM) instead of fine pitch (potential overspeed)] - that is, unless this is a prop set up for a multi-engine installation, which seems very unlikely. What am I missing here? |
Dan,
No, The temptation is strong, but I don't want to go there until I know what recourse options I can expect. I am getting conflicting advice as to whether to get the FAA involved in this or not. My natural tendency is keep experimental aviation free of Feds, lawyers, etc. However, this is a certified part and three fails in a short period is a GIGANTIC RED FLAG. This is a ticking bomb that when it goes off, you've got about 10 mins to get on the ground or be a glider with a seized engine. I guess I was lucky that the failure caused coarse pitch instead of overspeed, because the latter can trash an engine on top of everything else. As much as I would like to keep our community "pure", I would feel terrible if a failure of something I could have alerted to caused damage, injury, or death. Regardless of where this goes, they are going to want to examine the assembly as it is, not after an amateur inspection. It really needs to go to a NTSB level tombstone lab and before the tombstones are required. |
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Somewhere from a dark dusty corner of my memory I seem to recall that aerobatic planes use a different setup so that if the oil pressure is momentary lost, the prob does not go crazy.
Any chance you have a governor from an aerobatic application? MT is big in the aerobatic world. Or, maybe the cobwebs need sweeping.......?? |
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http://www.vansairforce.com/communit...9&postcount=20 |
Mike S, I am no expert, but you are on the right track wrt aerobatic CS props- the springs and counterweights that make low total drag, low rpm and high prop pitch with oil pressure loss are in the propellor, not the governor.
Is there a chance this RV-10 has a prop setup like an aerobatic plane? Is it possible that the same governor failure will overspeed a prop setup to go fine pitch/climb/high rpm and cause an acro/twin setup prop to go low rpm/coarse/high pitch? Prop should have limit stops with either setup in both directions? (Not an expert). I have seen nasty overspeeds in acro before accumulators and governors were all shaken down, limit serttings alone didn't stop overspeeds where counterweights were set for climb pitch/fine with oil pressure loss. |
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