231 crash on takeoff at 47N

[Brandt]

 

[toto]

Geez another Mooney crash at 47N.

[PeteMc]

@Brandt  This is old... May, 2023.  You can read about it in multiple places, here's one link:

https://asn.flightsafety.org/wikibase/312151

[toto]

3 minutes ago, PeteMc said:

@Brandt  This is old... May, 2023.  You can read about it in multiple places, here's one link:

https://asn.flightsafety.org/wikibase/312151

Ah .. okay it’s not another one

 

[Shadrach]

If indeed this was caused by loose and detached plug leads, having an engine monitor and knowing how to use it may have prevented this accident.

[Brandt]

Sorry. Didn’t mean to suggest it was recent but I hadn’t seen the video anywhere before. Maybe I missed that. 

[PeteMc]

18 minutes ago, Brandt said:

Sorry. Didn’t mean to suggest it was recent but I hadn’t seen the video anywhere before. Maybe I missed that. 

You may be right that the video wasn't posted before.  Here's the link to the original discussion about the crash here: https://mooneyspace.com/topic/45481-crash-at-47n-loss-of-power-on-takeoff-5-6-2023/ 

And there was another one there the year before in April, 2022: https://mooneyspace.com/topic/41940-bravo-lands-in-the-front-yard-of-a-new-jersey-home/  

Central Jersey is a nice little airport with inexpensive fuel (at least it was when I was back east).  But there are trees at one end and it always seemed like a smaller runway than it really is.  And not just because it's narrow, just where it sits gives it a funny visual impression.  At least to me. 

 

[Ragsf15e]

2 hours ago, Shadrach said:

If indeed this was caused by loose and detached plug leads, having an engine monitor and knowing how to use it may have prevented this accident.

This is related/unrelated, but one annual i had the left side of my engine, all the plugs only finger tight.  Mechanic set them there and got distracted as he was going back with a wrench (I believe it doesn’t require much, but apparently a little tighter is important).  Anyway, 2 or 3 flights later I started getting lots of radio noise/interference.  It sent me down a lot of rabbit holes, but the engine was running great.  One of the rabbit holes was to check the harness and we determined that the plugs (all 4 on the left) were barely attached to the harness. Yikes.

[toto]

16 minutes ago, Ragsf15e said:

This is related/unrelated, but one annual i had the left side of my engine, all the plugs only finger tight.  Mechanic set them there and got distracted as he was going back with a wrench (I believe it doesn’t require much, but apparently a little tighter is important).  Anyway, 2 or 3 flights later I started getting lots of radio noise/interference.  It sent me down a lot of rabbit holes, but the engine was running great.  One of the rabbit holes was to check the harness and we determined that the plugs (all 4 on the left) were barely attached to the harness. Yikes.

I had a similar thing happen after a major overhaul - but it was the lead wires that were only finger tight. Pulled the cowl and found the leads almost hanging off the plugs. That was after doing the first break-in flight. Ugh. 

[Ragsf15e]

1 hour ago, toto said:

I had a similar thing happen after a major overhaul - but it was the lead wires that were only finger tight. Pulled the cowl and found the leads almost hanging off the plugs. That was after doing the first break-in flight. Ugh. 

Ahh, my post wasn’t clear, mine was the leads as well.  Yeah, that doesn’t feel good after finding it. Scary.

[EricJ]

I wouldn't have thought you'd lose that much power from losing three plugs one one side with the others left.   I suspect there may have been more to it.

[Shadrach]

17 hours ago, Ragsf15e said:

This is related/unrelated, but one annual i had the left side of my engine, all the plugs only finger tight.  Mechanic set them there and got distracted as he was going back with a wrench (I believe it doesn’t require much, but apparently a little tighter is important).  Anyway, 2 or 3 flights later I started getting lots of radio noise/interference.  It sent me down a lot of rabbit holes, but the engine was running great.  One of the rabbit holes was to check the harness and we determined that the plugs (all 4 on the left) were barely attached to the harness. Yikes.

There are good mechanics, and there are not so good mechanics. I realized at some point halfway into ownership that it’s foolish to think that only the “not so good ones” make mistakes. Everyone makes mistakes, the difference between good and not so good are the processes used to reveal mistakes before the aircraft is returned to service.  
 

Several years ago, I noted an EGT increase on number one during climb out. This was a few hours after I had performed a plug rotation. Mag check revealed a miss. I was deeply disturbed to find that I had failed to tighten the lower plug lead on #1 which had completely detached. Not only did I not tighten it, but missed my mistake on final inspection before reassembly. I changed my process because of it. My leads are 90° elbows. I used to orient/angle all of the elbows by hand before tightening. I don’t do that anymore. 

[Jim Peace]

On 8/16/2024 at 2:11 PM, Shadrach said:

There are good mechanics, and there are not so good mechanics.

can someone provide a list of the good mechanics in central Florida?

[skykrawler]

I notice flaps were not in TO position.   Take off looked like right after rotation it struggled - too slow for no flaps.

Hard to believe a single plug could reduce power enough to cause an accident.

[Hank]

3 hours ago, skykrawler said:

Hard to believe a single plug could reduce power enough to cause an accident.

I had one plug lead go bad about two years after replacing the entire harness. Takeoff was longer than normal, but I was loaded for vacation with the wife and heavy, so didn't think about it. But boy, climb was really poor, like 200-300 fpm, well under half of what I was expecting. 

So I verified configuration, held at Vx and still couldn't get 500 fpm; lowered the nose to Vy and still very little climb. Checked throttle to WOT, checked Prop to Fine, checked mixture to Rich, flaps Up, gear Up, EGT was close to normal.

Went back and landed, taxied clear and did a run up--one side was 50 RPM drop, the other was 250. Something is wrong. Neighbor helped troubleshoot, found one cylinder was cold; cleaning and even swapping plugs did nothing, so we unloaded and went home. Caught up with my A&P later (none at my home field anymore), he diagnosed the bad lead, replaced it and magically the engine ran smooth and the plane climbed again.

So yes, losing one plug can be significant! It was a surprise to me, since the other plug in that cylinder was firing, but there was no way I could make a 3 hour trip like that, much less depart the grass strip that was my destination. 

[Hank]

3 hours ago, Aviationist said:

If one plug was firing the cylinder wouldn’t be cold. 
 

You were down a cylinder not a plug. (Though maybe caused by 2 plugs not firing)

 

losing 1 plug will not have that dramatic effect. Not if all systems are otherwise working normally. 

Only one lead was replaced (the top one), so the bottom plug must have been firing. But that cylinder was notably cooler after a 30-second uncowled run than the other three. He made marks on the exhausts, three disappeared, the fourth one didn't--then we made a very short run and could touch the one exhaust.

[Hank]

7 hours ago, Aviationist said:

What you are explaining is a cylinder with no plugs firing in it. 
 

you lost an entire cylinder. Not a plug. Loss of 25% of your power due to loss of a cylinder will cause what you describe. 
 

losing a single plug will not. Not in an engine that is working normally. 

Whatever you say. But only the lead from magneto to top plug was replaced, and then it worked and flew great.

So what made the bottom plug stop firing when the top one stopped, then magically restart when the top lead was replaced?

[Shadrach]

21 hours ago, Aviationist said:

If one plug was firing the cylinder wouldn’t be cold. 
 

You were down a cylinder not a plug. (Though maybe caused by 2 plugs not firing)

 

losing 1 plug will not have that dramatic effect. Not if all systems are otherwise working normally. 

A fouled plug or bad lead can reduce CHT and increase EGT significantly.  
Furthermore, they were ground running the engine between both, right and left mags.  Under such a scenario, I would expect the cylinder that was alternating between running on a single point of ignition and not running at all to be much cooler than the rest. Nothing in @Hank’s statement seems implausible. Maybe could have been worded more precisely, but it makes perfect sense.

[Hank]

7 hours ago, Aviationist said:

If you take off. And you have that significant reduction in power. That was not a single plug not firing. 
 

if you run it on the ground. Even for 2 minutes, and all your cylinders are firing, even on one plug, it’s going to be hotter. Not colder. 

I didn't run for 2 minutes on the ground with the cowling removed, just long enough to see if the marks burned off on all four exhausts. It remained visible on one, but a long run would have burned it off, too.

Regardless of your opinion,  replacing a single lead from magneto to plug resolved the issue, and normal climb rate returned on the first test flight afterwards. Surely you aren't saying that the other plug in that cylinder quit out of sympathy? We surely did nothing to it except clean it, then swap top to bottom, then swapped with the other cylinder on the right side; regardless of what we did, the same exhaust tube was noticeably cooler than the other three, with 250-300 RPM drop on one magneto.

[Shadrach]

28 minutes ago, Hank said:

I didn't run for 2 minutes on the ground with the cowling removed, just long enough to see if the marks burned off on all four exhausts. It remained visible on one, but a long run would have burned it off, too.

Regardless of your opinion,  replacing a single lead from magneto to plug resolved the issue, and normal climb rate returned on the first test flight afterwards. Surely you aren't saying that the other plug in that cylinder quit out of sympathy? We surely did nothing to it except clean it, then swap top to bottom, then swapped with the other cylinder on the right side; regardless of what we did, the same exhaust tube was noticeably cooler than the other three, with 250-300 RPM drop on one magneto.

Are you saying the engine was “missing” on that cylinder because of single plug failure? Perhaps the lack of heat fouled the remaining plug?

[Shadrach]

1 hour ago, Aviationist said:

I’m saying based on the symptoms that cylinder decided it wasn’t participating. It could have fowled, especially if it was the bottom one. But a fowled plug at what I assume is full power usually doesn’t clean itself out.  
 

That reduction in power is not the result of losing a single plug. It just isn’t. 

I was actually asking Hank for clarification regarding his specific scenario as I am trying to learn precisely how the events and symptoms he described came to be.

I agree that losing a plug should not reduce ROC by 500fpm.  I have flown my airplane with a dead mag and it performs reasonably.  The thing is though, single ignition performance can be greatly influenced by mixture.  If you have a dead mag, you can select a mixture setting that produces a faster combustion event to offset the single point of ignition propagation.  When you have an ignition issue on a single cylinder in climb, you don't have that option. 

Consider the following scenario:  hot day, mixture full rich,  Richest cylinders are already richer than optimal for conditions with both plugs operational. Then a plug fails on the richest cylinder. The combustion event speed on that cylinder is reduced by half but the piston speed remains constant.  Under such a scenario, I can envision a significant impact on climb performance, especially if operating near gross in summertime DAs.   In cruise, a lot of the deficit could be leaned away.  Indeed, depending on conditions, I might consider running all the cylinders single mag to ensure smoothness and uniform combustion until I could land.  Trying to maximize the power output of an engine with a plug failure on one cylinder is like trying to lean two different engines with a single mixture control.

[Hank]

46 minutes ago, Shadrach said:

I was actually asking Hank for clarification regarding his specific scenario as I am trying to learn precisely how the events and symptoms he described came to be.

I agree that losing a plug should not reduce ROC by 500fpm.  I have flown my airplane with a dead mag and it performs reasonably.  The thing is though, single ignition performance can be greatly influenced by mixture.  If you have a dead mag, you can select a mixture setting that produces a faster combustion event to offset the single point of ignition propagation.  When you have an ignition issue on a single cylinder in climb, you don't have that option. 

Consider the following scenario:  hot day, mixture full rich,  Richest cylinders are already richer than optimal for conditions with both plugs operational. Then a plug fails on the richest cylinder. The combustion event speed on that cylinder is reduced by half but the piston speed remains constant.  Under such a scenario, I can envision a significant impact on climb performance, especially if operating near gross in summertime DAs.   In cruise, a lot of the deficit could be leaned away.  Indeed, depending on conditions, I might consider running all the cylinders single mag to ensure smoothness and uniform combustion until I could land.  Trying to maximize the power output of an engine with a plug failure on one cylinder is like trying to lean two different engines with a single mixture control.

Yes, that sounds quite possible. I'm pretty sure that i didn't get much above 1000 agl in 3-4 minutes before giving up and going back.

After an hour's troubleshooting and identifying the cylwith the problem, we unloaded the plane back into the truck, pushed back into the hangar and called family while driving home that we wouldn't be there. Making a 10-hour each way drive just wouldn't work on a 4-day weekend.

The A&P diagnosed the problem and ordered the repair kit; since his field is a 45-minute drive, it all took two or three weeks to complete. It's been. Three years now, and no trouble since.

So I can see how the accident plane may have had trouble with initial climb with a single bad plug / ignition incident. Losing that much to a single plug surprised me, and apparently other readers here, but it's what happened. 

[flyboy0681]

I'm just curious of what your thoughts are about the following. What percentage of maintenance related crashes do you feel could have been avoided if the cowl opened up so that we could gain easy access?

[Shadrach]

26 minutes ago, flyboy0681 said:

I'm just curious of what your thoughts are about the following. What percentage of maintenance related crashes do you feel could have been avoided if the cowl opened up so that we could gain easy access?

I think the difference is overstated.  I would like better access, but I don't think the types of maintenance issues severe enough to cause a crash are going to be caught by most pilots.  If they were, Mooneys would be over overrepresented in the stats for off airport landings due to mechanical failure. IIRC they are above average in that category.

[kortopates]

10 minutes ago, flyboy0681 said:

I'm just curious of what your thoughts are about the following. What percentage of maintenance related crashes do you feel could have been avoided if the cowl opened up so that we could gain easy access?

I can only see it making a significant difference after major invasive maintenance and/or annuals. Not on any random flight. The vast majority of crashes are pilot error. But that said, not enough pilots do a RTS - Return to Service flight over a field before embarking on a long IFR or VFR flight.