NTSB Final Headscratcher: N304MA, 1997 M20K Encore Off Field Crash Landing Near Lakeway Airport

[skykrawler]

I have seen properly maintained spark plugs last 500hrs in a C182 with a Lyc 540.

If  my engine has a problem I'm heading right to the runway to be overhead and lose my altitude there.

[redbaron1982]

7 hours ago, JamesMooney said:

Sam Jewell, David Jewell

Don Maxwell, Paul Maxwell

sounds like a familiar problem with father-son businesses

Here in MS, we have people who consider some of those names you mentioned deities who can never make mistakes or who will always be the best.

If an airplane repaired by a well-known shop has an accident/incident, they would first challenge that the matrix had a glitch rather than the shop making a mistake.

[jetdriven]

You’ll have to search Jewell on this forum and other forums to understand what kind of reputation that place has. And it’s not you’re trying to hold them to some impossible standard, it’s just they have no standards at all.  We had a fresh jewell overhaul engine show up at our shop with the oil leaking from a blind bolt hole. Lycoming said replace the case half,  you can’t have oil coming out of a blind hole. Jewell said  smear some some glue in it. I had to tell the owner we couldn’t annual his airplane because there’s no way I can sign that off and I don’t think anybody with a conscience could either.

[AndreiC]

I have read so many stories about Jewell by now that I am puzzled how come the FAA is not coming down hard on them. At least two crashes discussed here had Jewell overhauls. People did not die, but that is mostly luck than anything else. We are not talking here about someone cheating with a couple hundred dollars, we're talking human lives at stake. Is this not what the FAA supposed to be looking for more than anything else?

[gevertex]

People need to call the FAA FSDO about Jewell. On my overhaul they failed to spot face the cylinder mounting flange under the bolt holes. This left excessive paint and caused my engine to start to come apart due to insufficient torque on the mounting bolts when the paint started to loosen from the cylinder. I would not be surprised if the same happened here. Someone should check for it. 
 

In addition, my case was heavily fretted. It’s likely it was fretted prior to the overhaul given the level fretting, they saw it and didn’t do anything about it putting me at risk for case failure down the line. 

[PT20J]

12 hours ago, gevertex said:

People need to call the FAA FSDO about Jewell. On my overhaul they failed to spot face the cylinder mounting flange under the bolt holes. This left excessive paint and caused my engine to start to come apart due to insufficient torque on the mounting bolts when the paint started to loosen from the cylinder. I would not be surprised if the same happened here. Someone should check for it. 
 

In addition, my case was heavily fretted. It’s likely it was fretted prior to the overhaul given the level fretting, they saw it and didn’t do anything about it putting me at risk for case failure down the line. 

So, what did the FSDO say when you called them?

[gevertex]

On 11/2/2024 at 10:01 PM, PT20J said:

So, what did the FSDO say when you called them?

Currently waiting for the inspector to get back with me.

[jlunseth]

"It's hard to say on this one, it could have been the low fuel set-up, combined with a pilot leaning during climb, which he might have been used to doing on a normally aspirated engine. Not good to do on a turbo engine. His low time with the airplane and possible mismanaging the engine may have been the ultimate cause. Or the engine just came apart at that point due to no one else's fault."

It is possible to get the TIT to exceed redline and get the engine into detonation territory in a few short minutes after takeoff in the TSIO 360 if you lean the engine at full power. Worse if the fuel is not setup properly. In fact, you can do this at any time during climb if you leave the power in full and back the red knob out far enough.

One cause is exactly what Lance says, the pilot is used to operating a normally aspirated engine and leans in the climb while the engine is making full power. The other is to fail to set the fuel knob to full rich right before takeoff, and the way that can happen is that you pull up to the hold short line, find out your takeoff is going to be delayed so you had the engine set full rich but now you back the knob off, and then you just forget to put it back in before taking off. If you don't catch it you will shortly see some magnificent temperatures, both TIT and CHT. Obviously can't say that is what happened here, maybe something did fail in the engine because of the prior work, but pilot error in managing the engine is possible.

[Marc_B]

https://data.ntsb.gov/Docket?ProjectID=106726

If you click though the docket, the aircraft had a JPI EDM700 and there was temp data recorded, although I don't see fuel flow data. 

https://data.ntsb.gov/Docket/Document/docBLOB?ID=16368357&FileExtension=pdf&FileName=ENGINE DATA MONITORS - SPECIALIST'S FACTUAL REPORT-Rel.pdf

https://data.ntsb.gov/Docket/Document/docBLOB?ID=16367961&FileExtension=csv&FileName=ATTACHMENT 1 TO ENGINE DATA MONITORS - SPECIALISTS FACTUAL REPORT-Rel.csv

15:54 there's a jump in EGT/TIT of ~100F, but then start to step down...  (this is what I typically see with a big mixture pull, then fine tune dial in my FF for desired power setting)

15:57 is when the temp for CHT6 starts to rapidly ramp up to 619F.  I'm not savvy with reading the raw data and extrapolating what was going on at the time.  But even when CHT6 was ramping up, the other CHTs were still mostly around 375-400F which seems to suggest something with cylinder 6.  It's also 20 minutes in and would seem in cruise after level off?  (vs accidently had mixture leaned and took off or leaning in the climb).

I'm not sure what a failure to enrichen on takeoff or a lean during the climb would look like...but from a novice (me) looking at this engine monitor data that's not what it seems to me...certainly there was something with Cylinder 6 that detonated out of control much different than any of the other cylinders.  Not sure you can explain this with spark plugs or magneto timing (issues noted in NTSB report) either??

EDIT:  not sure if the timestamps on the engine monitor accurately represent the ADS-B data from the flight track map in the original post...but it does appear that altitude was relatively constant at 7100...level off at 7500 and lean?

https://globe.adsbexchange.com/?icao=a32f42&lat=30.118&lon=-98.154&zoom=11.1&showTrace=2023-02-12&timestamp=1676216828

[wombat]

Based on this data, I have a hard time convincing myself this could possibly be the pilot's fault through engine mis-management.

Cylinder #6, that was the one that was damaged and experienced large fluctuations of exhaust and cylinder temperatures, was purely in the middle of the pack for CHTs before the runaway temperature event.  (two above, three below  Hottest: 411, #6: 386, coldest:353  And it was at that time the coldest EGT, at 1315 while the others were 1341 to 1446 (1341, 1370, 1375, 1392, and 1446 were the others) so it was not significantly out of the range of the others.

 

The most notable thing that is likely a pilot control issue is that within 30 seconds of #6 going from 'middle of the pack' to 'hottest' the EDM-700 was switched from "automatic" to "LeanFind" mode.   This indicates to me that the pilot was very likely messing with the mixture.   While there is no mixture data with the engine monitor data that is available to us, there is also no reasonable mixture setting that would cause the other cylinders to have no significant changes but #6 to have done this.

At 15:57:30 the engine monitor data switches from every 6 seconds to every second, but unfortunately that time frame is kind of critical.  It would have been great to have single second resolution from 15:56:30 to 15:57:30.  Oh well.

 

I'm wondering if maybe he was experiencing preignition on #6

[Will.iam]

couple of things about the jpi700 in the mooney I have did not have fuelflow it had a shadin fuelflow meter.  I had jpi install the fuelflow into the jpi700 as it was next to impossible to get my gami spread otherwise.  Second the jpi700 is defaulted to saving data every 6 seconds unless you change that in the settings menu but when you press the lean find button while it is active the jpi records data every second until you get out of that mode or it times out. most likely the jpi700 started flashing from the hot cylinder and the pilot probably pressed a button to step to that cyl info