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

[1980Mooney]

Final is out on the crash of the 1997 M20K Encore, N304MA, near Lakeway Airport on February 12, 2023.  The engine broke the #6 piston presumably due to detonation.  Causes listed are spark plugs worn out of spec, magneto timing out of spec, running lean.

The engine had a major Overhaul with new CMI cylinders May 24, 2019 by Jewel Aviation.

Don Maxwell Service Center inspected/gapped plugs and checked the magneto timing as part of the Annual on October 8, 2022. 

• Engine 278 hours since TSMOH. (Aircraft hours were 2732)

Dugosh did the Pre-Buy Inspection the week of January 17, 2023.

• Engine hours were 304 (Aircraft hours were 2758)
  • 26 hours after the Maxwell Annual - Dugosh claims that plugs are worn out

The accident was on February 13, 2023

• Engine hours were 309 (Aircraft hours were 2764 .)
  • 31 hours after the Annual by Maxwell

The new owner/pilot (Commercial, Instructor and Helicopter rated) did transition training

• At about 6,000 AGL and about 5 nm from Lakeway Airport he noticed
  • Fluctuating cylinder temperatures
  • Manifold pressure dropped to 26 in.
  • He could not increase manifold pressure
  • He had partial power and flew towards Lakeway, declaring an emergency
  • While on Final for the runway he lost all oil pressure.
  • He crashed short of the runway

So, we are to believe that only 31 hours and about 3 months later after Maxwell had their hands on the engine, the spark plugs wore out and the magneto got so badly out of time that it destroyed the engine?

I am having a hard time believing this.  The Right Mag was 22 degrees (only 2 degrees advanced over spec) and the Left Mag was 15 degrees (5 degrees retarded below spec).  The pilot commented that he had been running lean.

• Are we to believe that spark plugs will wear out in 25 hours?
• Are we to believe that Maxwell did not time the mags properly or that they went out of adjustment in 32 hours?

If one of the last M20K Encore's made by Mooney, maintained by Maxwell, inspected by Dugosh, flown by a Commercial and Instructor rated Pilot can't reliably make it back to the runway without crashing, what hope is there for 20-40 year older Mooney's in the hands of mere amateur weekend pilots like most of us?.....

N304MA | 1997 MOONEY M20K ENCORE on Aircraft.com

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/106726/pdf

Edited October 2 by 1980Mooney

[LANCECASPER]

I would be much more suspect of the Jewell engine overhaul than any of the rest of it.

Dugosh’s pre-buy notes show a missing bolt found in the engine?? How was the major overhaul done without replacing the turbo???

I wonder how many of the discrepancies on the pre-buy were fixed.

[flyboy0681]

"A review of data obtained from a J.P. Instruments EDM-700 unit onboard the airplane at the time of the accident showed an excessively high No. 6 cylinder head temperature reading about 17 minutes before the unit stopped recording data."

I wonder what "excessively high" means.

[1980Mooney]

1 hour ago, LANCECASPER said:

I would be much more suspect of the Jewell engine overhaul than any of the rest of it.

Dugosh’s pre-buy notes show a missing bolt found in the engine?? How was the major overhaul done without replacing the turbo???

I wonder how many of the discrepancies on the pre-buy were fixed.

ABSBExchange shows that the plane was in Kerrville for nearly a week in late January. Presumably it was at Dugosh doing the Pre-buy. That is plenty of time to address discrepancies. 
 

This should have been the best of the best of the best. The pinnacle of Mooney mid-body development managed/inspected by arguably 2 of the most experienced Mooney shops in the world flown by a 5000+ hour Commercial/ Instructor pilot. 
 

Instead this pilot came within about 4 feet of killing himself, crushed against the generator station. It’s amazing that the gash in the wing didn’t strike the fuel tank (full for the long relocation flight) and vaporize into an inferno. I think luck played a bigger role than skill that day.  And one of the few Encores wound up as scrap metal. 
 

[PT20J]

I would take the NTSB reports on GA accidents with a grain of salt. When I attended the Lycoming factory class there were a bunch of NTSB investigators there. They had the most interesting stories, like the toxicology report that came back from a deceased pilot that looked like an inventory for a pharmacy. But, the most interesting part was how overloaded they are. They all complained about the backlog of investigations and admitted that they often don't have enough time to get to the root cause. So, engine quit and it looks like it was disabled by detonation. Plugs look worn, timing was off, pilot operating LOP-- maybe those things caused it, maybe not. No time to try to figure it out. No one's going to cough up any more information anyway. Just note it and move on to the next report.

[Shadrach]

I am not buying that spark plug wear caused detonation.  I would like to have someone with an understanding of how combustion works explain that to me. Worn spark plugs are less likely to ignite the flame front not speed it up.  Preignition is a possible with plug damage.  Timing likely not the issue either. A delta of 2° is not likely a problem especially given the second plug was 5° retarded.  I would not be too quick to blame Jewell either.  As credentialed as this crew may have been, it appears that neither of them caught the elevated CHT until other symptoms manifested. I do not know what the stock engine instruments look like in an Encore.  Perhaps that info was not available due to the dim screen of the JPI.    If that was the case, then the pilot setting the power should have been smart enough to set the mixture very conservatively. 

[LANCECASPER]

30 minutes ago, Shadrach said:

I do not know what the stock engine instruments look like in an Encore.  Perhaps that info was not available due to the dim screen of the JPI.    If that was the case, then the pilot setting the power should have been smart enough to set the mixture very conservatively. 

The stock instruments were pretty sparse. In the one I had the factory installed JPI was over on the right.

(I had the yaw damper circled for another reason on the picture)


 

Questions run through my mind after this:

I’m also curious why the spark plugs worn beyond limits wasn’t listed as an A/W item. Also - whether the seller was willing to pay or not who takes off in a new-to-you airplane across the country with worn out spark plugs?

Also in looking at the flight path after a rough engine did he did he turn around to go back to Kestrel or Kerrville and then decide at the last minute to land at Lakeway? Nearest button on the GPS is there for a good reason.

Was he in a hurry to get the airplane back home and not have Dugosh set up the fuel system like it should have been (according to pre-buy)? Or some of the other discrepancies as well. Even though the airplane sat for a week in Kerrville on pre-buy, negotiations sometimes go back and forth and it doesn’t always mean that the shop has the time (or the parts) to do everything right away.

The turbo was high time and leaking oil and very doubtful it was replaced in that amount of time in Kerrville. I’ve always thought that a major overhaul included overhauling all of the components on the engine and the accessories.

 

[PT20J]

The picture of the plugs in the docket is not very useful because it does not show well the firing end and most of the plugs are turned so it is difficult to see the profile of the electrodes. However, from the little I can tell, they don't look that bad. Perhaps Dugosh used the go/no gauge and they slightly passed through the hole. Or maybe it was just the mechanic's observation that they were worn. Either way, I agree with @Shadrach that this didn't have anything to do with it. It just gave the IIC something to note in the report. 

[Shadrach]

1 hour ago, LANCECASPER said:

The stock instruments were pretty sparse. In the one I had the factory installed JPI was over on the right.

(I had the yaw damper circled for another reason on the picture)


 

Questions run through my mind after this:

I’m also curious why the spark plugs worn beyond limits wasn’t listed as an A/W item. Also - whether the seller was willing to pay or not who takes off in a new-to-you airplane across the country with worn out spark plugs?

Also in looking at the flight path after a rough engine did he did he turn around to go back to Kestrel or Kerrville and then decide at the last minute to land at Lakeway? Nearest button on the GPS is there for a good reason.

Was he in a hurry to get the airplane back home and not have Dugosh set up the fuel system like it should have been (according to pre-buy)? Or some of the other discrepancies as well. Even though the airplane sat for a week in Kerrville on pre-buy, negotiations sometimes go back and forth and it doesn’t always mean that the shop has the time (or the parts) to do everything right away.

The turbo was high time and leaking oil and very doubtful it was replaced in that amount of time in Kerrville. I’ve always thought that a major overhaul included overhauling all of the components on the engine and the accessories.

 

I've seen lots of engines with varying component times.  Let's say your turbo starts puking oil but the rest of the powerplant appears to have a lot of life left. Then it starts making metal 300hours later. Do you overhaul a 300hr turbo? Some do some don't.  If this one was puking oil, it reads like the last owner cheaped out at overhaul time.

[201Steve]

Wow…. A real shocker…. Another Jewell Aviation engine falling apart in flight.  I can’t believe it. 
 

[LANCECASPER]

6 hours ago, Brandt said:

And what does running leann have to do with anything?

It had been mentioned in this thread and on the report that the engine broke the #6 piston presumably due to detonation. 

Dugosh found during the pre-buy that the "Fuel System needs to be set up per TCM STD 97-3E". Many times on Continentals the fuel flow is not set up to provide enough fuel during the climb and the cylinders get very hot. 

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.

The cylinder coming apart was what they found, but the reason for that are just hypotheses now. We would all like to trace it back to the exact cause, but it doesn't look so simple on this one. If theres anything to learn from it I'd like to know.

[Brandt]

28 minutes ago, LANCECASPER said:

It had been mentioned in this thread and on the report that the engine broke the #6 piston presumably due to detonation. 

Dugosh found during the pre-buy that the "Fuel System needs to be set up per TCM STD 97-3E". Many times on Continentals the fuel flow is not set up to provide enough fuel during the climb and the cylinders get very hot. 

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 mismanaging the engine may have been the ultimate cause.

The cylinder coming apart was what they found, but the reason for that are just hypotheses now. If theres anything to learn from it I'd like to know.

I suppose that makes sense if the cylinder was lean enough to run at peak if the other cylinders were rich of peak. I was thinking LOP across the board and further leaning would cool that cylinder. Thx

[WilliamR]

Those issues from a Maxwell annual do not surprise me in the least. One of the many issues I corrected right after my annual/maintenance and TSIO360-sb engine installation with Maxwell was fuel flow setup and fuel line routing.  

Not sure why I even brought this up as there is a very clear bias on this board that Don Maxwell Aviation Services, Inc. can do no wrong. 

William

[AH-1 Cobra Pilot]

Be careful in your presumptions about the pilot having much experience.  How much of his time was in turbine helicopters, and how much was in recip airplanes?  A quick transition course will give you a SEL or MEL COMM + INST rating from a HELO  COMM + INST.

Flying C-12s in the Army, most of my colleagues were trained in helicopters first, then received a fixed-wing transition.  I was regularly annoyed by other pilots yanking back the throttles when told by ATC to descend from 21,000 to 19,000.  They seemed to have no appreciation of the stresses put on engines from their operating habits, let alone what it would do to a recip.

I have also seen a few poorly trained pilots ram a throttle to the stop on takeoff.  (Who the hell teaches this?)  They also get a lecture on taking care of engines.

[Yetti]

So it comes out of annual at Maxwell, then Dugash notes that the Fuel flow is not set properly several months later, then a lean condition causes detonation and the engine goes poof.    Seems like a maintainer and operator issue is at hand.

[LANCECASPER]

54 minutes ago, Yetti said:

So it comes out of annual at Maxwell, then Dugash notes that the Fuel flow is not set properly several months later, then a lean condition causes detonation and the engine goes poof.    Seems like a maintainer and operator issue is at hand.

Combine a slightly low fuel flow with a lean in the climb and I could see this happening. The report does list one of the causes as 'incorrect use/operation". It would be interesting to see the logs pages of what he had Dugosh do after the pre-buy.

We said it on the first thread about this accident, but it's worth repeating - he was able to walk away from it and that took skill on his part to get it down under horrible circumstances. He did not stop flying it until the airplane stopped. Under all of that stress he did not stall it or put it into a stall/spin. I would hope that if I was dealt the same hand that I would be able to do the same.

[1980Mooney]

1 hour ago, AH-1 Cobra Pilot said:

Be careful in your presumptions about the pilot having much experience.  How much of his time was in turbine helicopters, and how much was in recip airplanes?  A quick transition course will give you a SEL or MEL COMM + INST rating from a HELO  COMM + INST.

Flying C-12s in the Army, most of my colleagues were trained in helicopters first, then received a fixed-wing transition.  I was regularly annoyed by other pilots yanking back the throttles when told by ATC to descend from 21,000 to 19,000.  They seemed to have no appreciation of the stresses put on engines from their operating habits, let alone what it would do to a recip.

I have also seen a few poorly trained pilots ram a throttle to the stop on takeoff.  (Who the hell teaches this?)  They also get a lecture on taking care of engines.

 

18 minutes ago, Yetti said:

So it comes out of annual at Maxwell, then Dugash notes that the Fuel flow is not set properly several months later, then a lean condition causes detonation and the engine goes poof.    Seems like a maintainer and operator issue is at hand.

You may be right.  Although a 5,400 hour Commercial pilot that is a Helo pilot and a CFI, it is possible that he mismanaged the recip engine to the point that a piston disintegrated.  In his statement he said that he did not trust the JPI.  See his statement the last 2 pages.

https://data.ntsb.gov/Docket/Document/docBLOB?ID=17057139&FileExtension=pdf&FileName=NTSB Form 6120_1_Redacted-Rel.pdf 

It also unfortunate that he was not able to manage the engine out.  I have landed at Lakeway and it is a bit unnerving the first time under the best conditions. This experienced pilot had so much energy - altitude, speed and still partial power within 5 nm of the Lakeway.  He turned towards Lakeway and said oil pressure went to zero on downwind but the the engine was still turning until he was on base for short Final.

• When he was downwind for Runway 16, he said lost oil pressure,
• About midfield he was at 1,500 ft. AGL and 101 kts descending at -1,155 fpm.
• Later he was descending at -1,340 fpm and 105 kts while at 1,000 AGL
• By the time he was turning Base to Final he had lost too much energy and gotten too low and slow.

This highlights how difficult and dangerous an engine out is.  It is an event that killed Richard McSpadden.  This pro pilot survived.  We mere amateur weekend pilots may not be so fortunate.

https://data.ntsb.gov/Docket/Document/docBLOB?ID=17057139&FileExtension=pdf&FileName=NTSB Form 6120_1_Redacted-Rel.pdf

ADS-B Exchange - track aircraft live (adsbexchange.com)

 

 

[Yetti]

As I recall the first time this was discussed The track has some human factor of picking airports and oh crap I have to do something about this and get it down.    Like just kill altitude and speed and do a left pattern for LakeWay.   Combine that with a slippery Mooney and yep there will be some overshoot.   He walked away so he did pass the test, So there is no second guessing on my part.

Loss of oil pressure would mean partial power for awhile, then it will get quiet.

I've landed with three cylinders.   The most important part to practice is to go up high configure for takeoff then pull the power.   Your push over should be immediate then find best glide.

 

Still want to know how the fuel flow was not set coming out of the last several annuals.

"COMPLIANCE: At Engine Installation, 100 hour/Annual Inspection, fuel system component replacement or as required if operation is not within specifications. MODELS AFFECTED: All TCM continuous flow fuel injected engine models except IO-240-B w/ Bypass Fuel System; L/TSIO-360-RB; TSIO-520-L, LB, WB; GTSIO-520-F, K, N and GIO-550-A Engine Models. differences require checking and adjusting the fuel WARNING injection system to meet operational specifications before flight. "

 

Edited October 3 by Yetti

[LANCECASPER]

8 minutes ago, Yetti said:

As I recall the first time this was discussed The track has some human factor of picking airports and oh crap I have to do something about this and get it down.    Like just kill altitude and speed and do a left pattern for LakeWay.   Combine that with a slippery Mooney and yep there will be some overshoot.   He walked away so he did pass the test, So there is no second guessing on my part.

Loss of oil pressure would mean partial power for awhile, then it will get quiet.

I've landed with three cylinders.   The most important part to practice is to go up high configure for takeoff then pull the power.   Your push over should be immediate then find best glide.

 

Still want to know how the fuel flow was not set coming out of the last several annuals.

"COMPLIANCE: At Engine Installation, 100 hour/Annual Inspection, fuel system component replacement or as required if operation is not within specifications. MODELS AFFECTED: All TCM continuous flow fuel injected engine models except IO-240-B w/ Bypass Fuel System; L/TSIO-360-RB; TSIO-520-L, LB, WB; GTSIO-520-F, K, N and GIO-550-A Engine Models. differences require checking and adjusting the fuel WARNING injection system to meet operational specifications before flight. "

 

Usually the fuel system is sent out on an overhaul. I doubt that it was done on a bargain basement "overhaul" at Jewell.

The fuel system may have been looked at and adjusted by Maxwell and a few months and roughly 30 hours later by Dugosh but it still may not have been right after a few hours of flight if there were components that needed to be replaced.

It sounds like he took his transition training after the work done at the pre-buy by Dugosh so it was running right for awhile. Also it was flown safely from Longview back home and then a few months later down to Kestrel to be sold, and was flown safely from Kestrel to Kerrville.

[1980Mooney]

1 hour ago, Yetti said:

Still want to know how the fuel flow was not set coming out of the last several annuals.

"COMPLIANCE: At Engine Installation, 100 hour/Annual Inspection, fuel system component replacement or as required if operation is not within specifications. MODELS AFFECTED: All TCM continuous flow fuel injected engine models except IO-240-B w/ Bypass Fuel System; L/TSIO-360-RB; TSIO-520-L, LB, WB; GTSIO-520-F, K, N and GIO-550-A Engine Models. differences require checking and adjusting the fuel WARNING injection system to meet operational specifications before flight. "

 

1 hour ago, LANCECASPER said:

Usually the fuel system is sent out on an overhaul. I doubt that it was done on a bargain basement "overhaul" at Jewell.

The fuel system may have been looked at and adjusted by Maxwell and a few months and roughly 30 hours later by Dugosh but it still may not have been right after a few hours of flight if there were components that needed to be replaced.

It sounds like he took his transition training after the work done at the pre-buy by Dugosh so it was running right for awhile. Also it was flown safely from Longview back home and then a few months later down to Kestrel to be sold, and was flown safely from Kestrel to Kerrville.

All interesting.  The Aircraft, Engine and Prop Logs are in the Docket from 2018 on to the time of the accident.  

• This Encore was owned by PA Aviation LLC in Burleson, TX from 2012 to just before the accident on February 12, 2023
• The plane was in Kerrville (presumably Dugosh) from January 16-23, 2023 and then returned to Kestrel
• The new owner (Commercial & Helo Pilot/CFI owner and PIC during crash) appears to be flying transition training on February 11, 2023 - the day before the accident
  • The plane flew from Kestrel in 6 legs eventually back to Kestrel - total duration 6.5 hours
  • ADS-B Exchange - track aircraft live (adsbexchange.com)
• While owned by PA Aviation LLC, the owner seemed to have mostly the "best of the best" work on the plane
  • All Annuals were done by Maxwell during the entire period (before and after the Overhaul)
  • In July 2019 Maxwell performed the Overhaul with the engine done by Jewel
  • In August 2019 LASAR in California worked on the plane - entry says
    • " tightened most of the induction clamps.  Set MP to 39" @ Full Power"
    • "replaced TIT probe and OPS check normal on JPI"
  • In September 2019, for some reason, Maxwell worked on the TIT probe again
  • In February 2021, Maxwell installed Garmin G5's and GFC500 autopilot and removed the vacuum system.
  • https://data.ntsb.gov/Docket/Document/docBLOB?ID=17141507&FileExtension=pdf&FileName=Engine Maintenance Records - 2018 to Accident_Redacted-Rel.pdf
  • https://data.ntsb.gov/Docket/Document/docBLOB?ID=17141169&FileExtension=pdf&FileName=Airframe Maintenance Records - 2018 to Accident_Redacted-Rel.pdf
  • https://data.ntsb.gov/Docket/Document/docBLOB?ID=17141070&FileExtension=pdf&FileName=Propeller Maintenance Records - 2018 to Accident_Redacted-Rel.pdf
• Although not in the Logs, Dugosh performed the Pre-Buy January 16-23, 2023

This did not appear to be a neglected plane.  Maxwell and LASAR are not "bargain basement" providers.  A lot of really experienced Mooney mechanics had their eyes and hands on this Encore right up to the time of the accident.  

How could this 300+ hour engine be in such bad shape?

 

Edited October 4 by 1980Mooney

[LANCECASPER]

4 hours ago, 1980Mooney said:

 

• • In July 2019 Maxwell performed the Overhaul with the engine done by Jewel

Don Maxwell Aviation may have taken off the engine and re-installed it after the overhaul, but the owner gets to choose who does it. Also from what I hear that when Sam Jewell used to do a lot of the work they did a good job, but not so much with the son David Jewell.

I like a deal like everyone else, but considering the wide definition of an "overhaul", it's hard to imagine choosing the lowest bidder in the country who does the absolute minimum to do the engine on a high value airplane like this.

By the way www.jewellaviation.com doesn't take you to Jewell Aviation anymore, although I like the fuels prices on their field (https://airnav.com/airport/KTKX/A3).

[Pinecone]

It could also be some other cause.   We had a cylinder detonate in a O-470 (C-182).  No apparent reason, about 5 minutes after takeoff.

 

 

[JamesMooney]

On 10/3/2024 at 8:34 AM, WilliamR said:

Those issues from a Maxwell annual do not surprise me in the least. One of the many issues I corrected right after my annual/maintenance and TSIO360-sb engine installation with Maxwell was fuel flow setup and fuel line routing.  

Not sure why I even brought this up as there is a very clear bias on this board that Don Maxwell Aviation Services, Inc. can do no wrong. 

William

A big issue these days is that the older generation are semi-retiring and leaving it to the younger generation who may or may not be as involved. I didn’t see Don much, until the plane he sold me had a $20k in mistakes. Before then, it was all his unsupervised apprentices. After that, he slowly showed up. 

Edited October 18 by FlyingCanuck

[JamesMooney]

On 10/3/2024 at 9:37 PM, LANCECASPER said:

Don Maxwell Aviation may have taken off the engine and re-installed it after the overhaul, but the owner gets to choose who does it. Also from what I hear that when Sam Jewell used to do a lot of the work they did a good job, but not so much with the son David Jewell.

I like a deal like everyone else, but considering the wide definition of an "overhaul", it's hard to imagine choosing the lowest bidder in the country who does the absolute minimum to do the engine on a high value airplane like this.

By the way www.jewellaviation.com doesn't take you to Jewell Aviation anymore, although I like the fuels prices on their field (https://airnav.com/airport/KTKX/A3).

Sam Jewell, David Jewell

Don Maxwell, Paul Maxwell

sounds like a familiar problem with father-son businesses

[LANCECASPER]

5 hours ago, JamesMooney said:

Sam Jewell, David Jewell

Don Maxwell, Paul Maxwell

sounds like a familiar problem with father-son businesses

From what I understand, Paul Maxwell handles the avionics end of the business. Lynn Mace an A&P/IA, who used to own a Mooney Service Center himself, oversees the shop. Don Maxwell owns the business. 

I'm sure no shop is perfect, and no shop finds every squawk, but comparing how Jewell handled overhauls and closed down, to Maxwell Aviation who does a couple hundred Mooney annuals a year and helps many people calling for advice, free of charge, is not a fair comparison.