Sanoi Posted November 21, 2020 Report Posted November 21, 2020 (edited) This happened after a 36K Overhaul. Analysis During cruise flight, the pilot noticed an increase in cylinder head temperature on two cylinders and unsuccessfully attempted to reduce the temperature. He reported that he soon heard "an explosion" and noted a hole in the engine cowling. He performed a forced landing to a golf course, during which the landing gear collapsed, which resulted in substantial damage to the right wing. Postaccident examination of the engine revealed that the Nos. 1 and 2 connecting rods exhibited thermal discoloration consistent with a loss of lubrication. Additionally, the breakaway torques measured at 8 of the 12 through-bolts showed that they were below the manufacturer's specifications. The No. 2 main bearing saddles exhibited impingement damage, and the No. 2 bearing was partially rotated clockwise, which blocked the oil passages leading to the connecting rod bearings. The mating surfaces of the main bearing saddles had remnants of silk thread around the through-bolt holes, which was contrary to manufacturer guidance that prohibited placing silk thread in these areas. Given this information, it is likely that maintenance personnel applied silk thread to a prohibited area during an engine overhaul that occurred about 255.8 flight hours before the accident. This resulted in a loss of torque on the crankcase through-bolts, which allowed the No. 2 main bearings to shift, resulting in restriction of lubrication to that area and subsequent engine failure. Probable Cause and Findings The National Transportation Safety Board determines the probable cause(s) of this accident to be: Maintenance personnel's improper assembly of the engine during overhaul, which resulted in lubrication restriction due to a bearing shift and the subsequent engine failure. http://www.kathrynsreport.com/2020/06/loss-of-engine-power-total-mooney-m20k.html?m=1 Edited November 21, 2020 by Jonás Quote
carusoam Posted November 21, 2020 Report Posted November 21, 2020 Welcome aboard Jonás... Are you looking for a better source for an engine OH? We have some preferred suppliers for that... Best regards, -a- Quote
hammdo Posted November 22, 2020 Report Posted November 22, 2020 Wow, I’d be unhappy too. @Jonás, I see it is your plane, what has the engine shop (BTW, who did your overhaul?) decided to do? I’m assuming it’s not totaled. -Don Quote
toto Posted November 22, 2020 Report Posted November 22, 2020 Good on the NTSB. I get almost numb to reading one accident report after another where the pilot made some series of mistakes that led to a preventable accident. Here's an honest-to-goodness maintenance issue that resulted in an off-field landing, and four people walked away. But the NTSB clearly took it very seriously and put a lot of effort into a root cause determination. 2 Quote
toto Posted November 22, 2020 Report Posted November 22, 2020 18 hours ago, Jonás said: 36K Overhaul. What's a 36K overhaul? [ETA: Aaah, he may be saying he spent $36k on the overhaul...] Quote
Sanoi Posted November 22, 2020 Author Report Posted November 22, 2020 The Overhaul was performed by Pine Mountain Aviation of Connecticut. They have been around for a long time and have a good reputation. Quote
Sanoi Posted November 22, 2020 Author Report Posted November 22, 2020 Yes, unfortunately there was a ditch on the fairway. The plane was total. If you see the pictures of the engine, you will find a 2in hole. Quote
hammdo Posted November 22, 2020 Report Posted November 22, 2020 Oh totaled, damn... saw the hole. she looked like a great bird too... -Don Quote
toto Posted November 22, 2020 Report Posted November 22, 2020 6 minutes ago, Jonás said: Yes, unfortunately there was a ditch on the fairway. The plane was total. If you see the pictures of the engine, you will find a 2in hole. Yuck. So the gear collapsed when you rolled through the ditch? Quote
carusoam Posted November 22, 2020 Report Posted November 22, 2020 This was a thread from the time the accident occurred.... I believe they are related... Great to see you stop in to MS, Jonás! I reread the thread... to see what the thoughts were at the time... 1) Great airmanship! 2) I don’t think anyone could even guess your mechanical issues would be the challenge... Best regards, -a- Quote
Sanoi Posted November 23, 2020 Author Report Posted November 23, 2020 Thanks for sharing the link to the early postings regarding the accident. The incident attracted a lot of attention because of the AOPA and PBS report that was released just 5 days before the accident and because of the 5.2 M I got for my HS school to start an aviation program in the heart of NYC. Indee landing was challenging. Primarily because of the the low altitude we were flying at, under class B at only about 1500 to 1600 ft. However, all pilot are trained to deal with emergencies like this one. In my case, I was lucky enough to spot a golf course a few miles away. I feel that Luck is a deterning factor. 6 1 Quote
Sanoi Posted November 25, 2020 Author Report Posted November 25, 2020 Searching the Internet I found this pilot account about an accident with another engine that was Overhaul the same company that did mine. http://newlangsyne.com/enginefire/index.htm 1 Quote
carusoam Posted November 26, 2020 Report Posted November 26, 2020 That’s quite a write-up! Best regards, -a- Quote
GeeBee Posted November 28, 2020 Report Posted November 28, 2020 What I don't understand is who would put anything, anything at all near main bearing journals that were to be mated and think that was a good idea. I've seen silk thread used around the periphery of the case halves for the sealant, but the main journals? Why would you do that? What is going to leak and why would you care if it leaked, it is supposed to be in oil and lots of it. Quote
N201MKTurbo Posted November 28, 2020 Report Posted November 28, 2020 53 minutes ago, GeeBee said: What I don't understand is who would put anything, anything at all near main bearing journals that were to be mated and think that was a good idea. I've seen silk thread used around the periphery of the case halves for the sealant, but the main journals? Why would you do that? What is going to leak and why would you care if it leaked, it is supposed to be in oil and lots of it. I just read the Lycoming service instruction regarding case sealing. It says which sealants to use and where to put the silk thread. There is a whole paragraph in red that talks about the prohibition of putting sealant or silk thread around the through bolts. Apparently it has been a problem for a long time. Some mechanics think it will keep the engine from leaking oil. They say doing this will lead to loss of clamping force and engine failure. You would think the engine shops would be required to be trained on this stuff. Quote
N201MKTurbo Posted November 28, 2020 Report Posted November 28, 2020 I wonder how many more engines that were done by this shop are ticking time bombs. 1 Quote
GeeBee Posted November 28, 2020 Report Posted November 28, 2020 I can't believe the FAA has not issued an AD on this shop's engines, unless it has been verified this is a one off. Quote
N201MKTurbo Posted December 2, 2020 Report Posted December 2, 2020 On 11/30/2020 at 12:41 AM, Ventus4 said: Enjoy :-) This wasn’t a maintenance mistake, this was a conscious effort to do something that is specifically prohibited in a service bulletin. Quote
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