Bent prop:Dial vs Teardown

[Jerry Cochran]

I'd like to get some input from all Lyco experts out there. Let's say you have an O-360 just overhauled by a VERY reputable and well known shop. Then at under 50 hours, just well broken in, one has a mishap and bends prop.

According to Lyco, this engine MUST be torn down, inspected, and put back together with new bearings, etc. Other licensed shops say just dial the crank flange and if OK, go and fly.

I've also noted chatter in the various forums like "Well, what's it dial?" implying that just dialing it is "good enough" Please help me lower the confusion...

I am looking at an engine that had this problem, just trying to find it's worth.

Jerry

[vic syracuse]

Sudden stoppage with enough force to bend the prop also puts undue stress on other "spinning" components, such as those attached to the accessory case, like Magnetos. There are drive pins back there that can get stressed/bent. Sure, there are examples out there of those who have not done a teardown aafter a sudden stoppage, and they have not had any problems. I personally am aware of one that braked too hard on grass, went up on the nose and back down, bending the prop and minimal cowl damage. NO teardown, and it has flown for 7 years now without a problem. If it was mine, I would have torn it down before I put my family in it. Everyone's level of risk is different. You might also ask the insurance company if they would require it to be torn down.

Vic

[Andy Hill]

Let's say you have an O-360 just overhauled by a VERY reputable and well known shop. Then at under 50 hours, just well broken in,

Not too sure of the relevance of any of this The engine is now unusable IMHO.

If there were any mitigating factors, where some might consider of a pragmatic view, they would along the lines of wooden prop? Grass? Low RPM? Even then a strip down is the "correct" action I think...

Just my 2cs worth

[videobobk]

In trying to determine its worth, I would say first dial it in. If the crank isn't bent, then it is worth (IMHO) somewhat more than core value. The cylinders should be good. It should be torn down, however, and there MAY be other parts needing replacement. It the crank is bent, it is worth less than a basic run-out core at least to me.

Bob Kelly

[Mel]

One of the main concerns with a prop strike is that no matter how minor it seems, it still stressed the spinning internals of the engine. Especially the drive pin and attachment hardware at the accessory drive end.
Lycoming says a tear down is required.
Yes, there are probably some good usable parts. But I certainly wouldn't put my Family behind it without a proper tear down and inspection. (That's of the engine, not the Family)

[Ron Lee]

Originally Posted by Mel

. But I certainly wouldn't put my Family behind it with a proper tear down and inspection.

I am sure he means WITHOUT a proper tear down and inspection.

Ron "never maks tipos" Lere

[Mel]

Originally Posted by Ron Lee

I am sure he means WITHOUT a proper tear down and inspection.

Ron "never maks tipos" Lere

Thanks. That wasn't a mistake. It was a test!
You passed.

[pvans]

Both Lycoming and Continental require a tear down inspection if the prop is damaged. All sorts of stuff CAN happen inside. You could get lucky but you also could not. Most any insurance company will pay for the tear down and rebuild , assuming there was insurance.

Personal experience. We have a 172 with an O-300. Parked, tied down. A freak gust of wind picks up the tail ( no rope there), lifts plane, strains a wing rope which breaks, stands plane up on the tripod of it's nose, left gear and left wing tip. 20 minutes later another gust blows it the other way and it lands on it's gear with a bunch of folks standing around watching. It was a sunny day, not a cloud in the sky( eastern Washington), and my son was only going to town for 2 hours. The 182 next to him flipped over on its back, no tie downs at all.

We removed the spinner which was cracked, ( one tip of prop was bent a tiny bit from contact with the asphalt), duct taped the wing tip, got a ferry permit, test ran it like crazy, and he flew it 2 hours home with no effect on flight at all.

We then removed the wing for repair to the outboard 5 feet. Insurance company wanted to tear down the engine, I said that seemed silly, it only had 600 hours and was not running. They paid for wing repairs, a prop overhaul, a new spinner and all my labor ( I am an A&P with IA). We flew happily into the sunset....UNTIL....8 flying hours later when the oil change came due. The screen was FULL of chips of aluminum.

Called the insurance company back, they said, go ahead and remove it and have engine shop tear into it. The shop found the piston pin cap on cyl 1 and 2 were worn down to a small pea size. No explanation given. I bought 6 new cylinders and spark plugs, and had the mags looked over, the insurance company paid for all the rest. We have a fresh overhaul now.

What caused this? Ins. Co hired an engine expert, he came to no conclusions. I suggested that since the airplane stood on its nose for 20 minutes all the oil drained forward and some got behind the piston pin caps, then when the engine ran, the pressure from heat pushed them against the cylinder wall and ground the soft aluminum to bits against the hard steel cylinder. They decided they could neither prove nor disprove my theory and decided to pay the claim since we had a record of clean oil prior to the incident. ( AIG, in spite of their financial track record they treated us right)

All I am trying to say here is that an engine pedigree is important. If you don't know the history of good engine operation then you have to be suspect.

[David Clifford]

I purchased an IO-540 that was a prop strike. The flange dialed .008". I disassembled engine per Lyc SB and sent all the required parts out for inspection/repair. The crank was straightened (thank god!) for about $900 with a yellow tag. All the other parts passed inspection and were yellow tagged. This was a low time engine, 491 hours SNEW with just a little over 100 hours since factory crankshaft SB compliance which included all new bearings ect.. I replaced the rod bearings/bushings. and just freshened up the cylinders before reassembly with required new bolts, ect... I got about $3000 into the teardown and reassembly. Granted its now an experimental IO-540, but I got lucky and now have a late model 2001 Lycoming for under $16K.

[Jerry Cochran]

Great comments/wisdom,so keep 'em coming...

Jerry