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Clogged Oil Sump Suction Screen Fatal Accident

Tandem46

Well Known Member
Recent horrific fatal accident directly contributed to the failure to clean the oil suction screen and the resulting loss of oil pressure. (Screen shot from accident aircraft)

48-CD7-E21-16-DF-4527-9-AC1-6268-A1-A8-BA4-D.jpg


Full story here:
http://www.kathrynsreport.com/2021/02/piper-pa-32rt-300t-turbo-lance-ii.html

There is a very recent thread on the oil sump suction screen located below but I didn’t want this accident getting buried in that thread given its critical importance and the fact that many operators don’t even realize there is a suction screen.
https://vansairforce.net/community/showthread.php?t=203529
 
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How do you draw the conclusion that the screen caused the engine failure?

Lycoming SB 480F specifies that the cleaning of the sump screen, oil filter examination as part of "changing the oil". Despite this instruction, the first time that I changed the oil or my certified airplane that had been maintained by a professional shop - the sump screen was so full that I could not push it out. Never seeing this before I ran to my engine shop fearing that I bought a boat anchor. The shop manager just laughed saying that it was carbon and not abnormal! I couldn't believe that, as we discussed normal shop practices he simply stated that although a good shop will do IAW "oil change" SB , most don't! I imagine apart from the experimental world where we tend to be more diligent about doing thing right; that the average shop maintained airplane looks more like your pictures. :mad:

I join you in highly recommending that it gets cleaned IAW, but I don't see it as the cause of said engine failure. Perhaps I read too fast?

Thanks,
 

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Just curious but if the screen is blocked is there some form of oil bypass?
Figs

NO. It sits in the only path from sump to oil pump inlet. There is a small bit of leakage around the screen, but that also will clog up with carbon chunks if that is the clogging source.
 
The NTSB drew the conclusion. Lycoming had an input.

A high percentage of the material in the posted photo is actually metal, per the lab report. That's probably from the failed components, given the report also states the pilots told ATC the engine had failed but the prop was turning.

Although an engine failure, it should have resulted in a forced landing, not a crash (the terrain around Selma offers lots of flat fields). Things literally went to h**l when a seized rod knocked a hole in the case, starting an engine compartment fire, which appears to have lit off material behind the panel via hot firewall "fire transfer". See section 2.1
 
Thank you,

I saw it as carbon, thanks for showing me otherwise.

Not withstanding, I can't believe all shops don't clean it with each oil change or at least annual! I had 2 engine, maintained (or not) for the life of the engine by certified shops & personal, yet on my 1st oil change there was so much carbon that literally, I had to run a drill through the screens to start to get the carbon out. :mad: yet, homebuilders get a bad rap in many certified shops !
 
To save someone from having to look it up, that screen bolt/housing requires an AN900-16 (MS35769-21) asbestos gasket (crush washer) when you service the screen. Just did it a few days ago on my IO-320.
 
I would be utterly shocked to inspect my screen and find that. I check mine with each oil change and have never found a speck of anything!
 
To save someone from having to look it up, that screen bolt/housing requires an AN900-16 (MS35769-21) asbestos gasket (crush washer) when you service the screen. Just did it a few days ago on my IO-320.
Edit: Correction to my post, the screen does exist on the IO-390-EXP119 and it is under the sump, so a different location but it does exist.
 
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The NTSB drew the conclusion. Lycoming had an input.

A high percentage of the material in the posted photo is actually metal, per the lab report. That's probably from the failed components, given the report also states the pilots told ATC the engine had failed but the prop was turning.

Although an engine failure, it should have resulted in a forced landing, not a crash (the terrain around Selma offers lots of flat fields). Things literally went to h**l when a seized rod knocked a hole in the case, starting an engine compartment fire, which appears to have lit off material behind the panel via hot firewall "fire transfer". See section 2.1

This is a great example why it's smart to follow Dan's recommendations on insulating your firewall.

Dan, Any chance you can replace your missing photos in the thread below?

https://vansairforce.net/community/showthread.php?t=112905&page=2
 
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So awful

Cherokee 6 has a baggage compartment between the firewall and the front bulkhead of the cabin. Must have been a really nasty fire to burn its way aft of the baggage compartment.
I pull the suction screen on our RV-6 every second oil change. If I’m working on someone else’s airplane and I don’t know when the screen was pulled last, I get it out. Oddly, I rarely find anything there and when I do it’s just a couple/few flakes of carbon. I’ll keep checking, of course.
 
Engine log

The report states that "The airplane was equipped with an Electronics International MUX-8A engine monitor. A device that was similar to the design that was impact damaged was retained to be sent to the NTSB Recorders Laboratory. "
There is no engine log data in the report from the impact damaged engine monitor.
Such data would be informative for oil pressure, oil temperature, CHT, prior to the point when there was a catastrophic engine failure. Sadly, it won't bring back the accident pilots, but it could help others.
 
Cherokee 6 has a baggage compartment between the firewall and the front bulkhead of the cabin. Must have been a really nasty fire to burn its way aft of the baggage compartment.

Pure speculation...the nose gear well provides a direct connection to the cabin.
.
 

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Suction Screen

This was a turbocharged engine and I would speculate that those engines make more carbon than normally aspirated. Have never found many particles or chunks in the suction screen on engines that the screen gets checked regularly. Have seen a couple that had a lot.

Don Broussard
RV9 Rebuild in Progress
57 Pacer
 
If it only had a low pressure switch . . .FYI

Some people may not know, but an oil pressure switch that is set so it will not alarm at idle is not a valid oil pressure alarm for full power operation.

Oil flow is primarily to keep the bearings cool and pressure provides that flow at cruise and TO RPM. A pressure alarm switch that is set for idle rpm to avoid nuisance alarms will not provide sufficient oil pressure/flow at rated rpm. The bearings will begin to heat and score and all the while there will be just enough pressure to keep the alarm off.

I have seen a couple of instances where this happened and the alarm only went off after the engine was already toasted.

I do not know how this aircraft oil alarms were set.

Our panels have the computation ability to set an idle and cruise speed oil pressure alarm, but don't. This would be a good feature to add in the future.

Just an FYI.
 
Some people may not know, but an oil pressure switch that is set so it will not alarm at idle is not a valid oil pressure alarm for full power operation.

Oil flow is primarily to keep the bearings cool and pressure provides that flow at cruise and TO RPM. A pressure alarm switch that is set for idle rpm to avoid nuisance alarms will not provide sufficient oil pressure/flow at rated rpm. The bearings will begin to heat and score and all the while there will be just enough pressure to keep the alarm off.

I have seen a couple of instances where this happened and the alarm only went off after the engine was already toasted.

I do not know how this aircraft oil alarms were set.

Our panels have the computation ability to set an idle and cruise speed oil pressure alarm, but don't. This would be a good feature to add in the future.

Just an FYI.

Great thought Bill and agree 100%, you should post this in the G3X wish list thread.
 
I just put half a dozen MS35769-21 crush washers in my Spruce basket.
Will do the inspection at annuals.

My oil pressure alarm whistles at 25 PSI or below.
Idle pressure is 75 ish...
 
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Piper

Piper firewalls and firewall components are about as far as one can go in the opposite direction of Dan's excellent research and ideas. The Piper photo posted appears to have aluminum rivets. Piper in the early Cherokees as well as others used some type of putty around firewall pass thru's. My recollection is that most single Pipers had galvanized firewalls.
It appears from the accident report that the fuel selector was not turned off. In a turbocharged single engine airplane you may only have a few seconds to shut off the fuel. Less critical with normally aspirated but still very important.
One poster referred to the accident airplane as a Cherokee 6. Technically it was a Piper Lance, later renamed Saratoga.
 
Heat

Wouldn't such restricted flow cause the engine to run hot and incrementally hotter for several hours prior to failure? Seems like the carbon build up would have gotten worst over time and the oil restriction along with it. I would think there would have been many warning signs prior to the catastrophe.

I hate seeing this kind of stuff- hopefully some lessons to learn in addition to checking that screen at least every annual, if not with every oil change. I ordered some crush washers too.
 
Some people may not know, but an oil pressure switch that is set so it will not alarm at idle is not a valid oil pressure alarm for full power operation.

Oil flow is primarily to keep the bearings cool and pressure provides that flow at cruise and TO RPM. A pressure alarm switch that is set for idle rpm to avoid nuisance alarms will not provide sufficient oil pressure/flow at rated rpm. The bearings will begin to heat and score and all the while there will be just enough pressure to keep the alarm off.

I have seen a couple of instances where this happened and the alarm only went off after the engine was already toasted.

I do not know how this aircraft oil alarms were set.

Our panels have the computation ability to set an idle and cruise speed oil pressure alarm, but don't. This would be a good feature to add in the future.

Just an FYI.

Bill,
I was asked about this yesterday on a flight. I remembered from you or someone exactly what you are saying here. When I pull power on landings or stall practice, I get the low oil pressure warning on my g3x. Glad it is working properly!
 
Oil suction screen

A friend with a 260 Comanche was doing his annual, so I offered to pull and clean his suction screen. There was carbon/lead buildup, nothing magnetic, and seemed to crush into powder. Afterwards, his oil pressure was significantly higher, he was able to back off his oil pressure relief valve that his mechanic had been bumping up over the years!
 
A friend with a 260 Comanche was doing his annual, so I offered to pull and clean his suction screen. There was carbon/lead buildup, nothing magnetic, and seemed to crush into powder. Afterwards, his oil pressure was significantly higher, he was able to back off his oil pressure relief valve that his mechanic had been bumping up over the years!

Based on the NTSB data on this accident, this is what happened here as well. It seems that there are a lot of mechanics that don't know that the Lycoming has this cleanable suction screen, probably because Continental does not have one.
 
Anyone care to share pictures of how they safety wired the nut when back in place. That was not easy ,and I have heard that is in part some of the reason shops avoid doing this task at annual.
 
Anyone care to share pictures of how they safety wired the nut when back in place. That was not easy ,and I have heard that is in part some of the reason shops avoid doing this task at annual.

If a shop avoids a standard (required) inspection because of safety wire difficulty, this would be a shop to avoid entirely.
 
If a shop avoids a standard (required) inspection because of safety wire difficulty, this would be a shop to avoid entirely.

Agreed. There is nothing difficult about safety wire on that plug. I check mine every annual.
 
Afterwards, his oil pressure was significantly higher, he was able to back off his oil pressure relief valve that his mechanic had been bumping up over the years!

That is really sad that a professional mechanic would see consistently dropping oil pressure and not check the screen for blockage. So glad that I have an EAB aircraft.

Larry
 
Anyone care to share pictures of how they safety wired the nut when back in place. That was not easy ,and I have heard that is in part some of the reason shops avoid doing this task at annual.

Not hard to get to the plug and safety wire on the RVs. Some planes (lycoming Mooney’s) are very difficult.

Don Broussard
RV9 Rebuild in Progress
57 Pacer
 

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Not hard to get to the plug and safety wire on the RVs. Some planes (lycoming Mooney’s) are very difficult.

Don Broussard
RV9 Rebuild in Progress
57 Pacer

Maybe not hard when the engine isn't installed!
Every RV is different, some are not so bad while others have terrible access, depends on many factors.
Ever check an RV7 with inverted oil?
 
Maybe not hard when the engine isn't installed!
Every RV is different, some are not so bad while others have terrible access, depends on many factors.
Ever check an RV7 with inverted oil?

Or an RV-10 with the Barrett cold-air sump?

-Marc
 
Or an RV-10 with the Barrett cold-air sump?

-Marc

Just a data point - the Superior cold air sump has the suction screen access at the back right, and it comes out straight towards you when working on the right side of the engine - very convenient. Even still, it takes care to get the screen back in properly. The safety wire is easy to install.

I think it would be great if we all did a video showing how to do this and put it on youtube, with a hashtag like #suctionscreen to hopefully get more owners, operators, and mechanics to become aware of this requirement, and to check their suction screen.
 
I think it would be great if we all did a video showing how to do this and put it on youtube, with a hashtag like #suctionscreen to hopefully get more owners, operators, and mechanics to become aware of this requirement, and to check their suction screen.

This would be great!
 
I think it would be great if we all did a video showing how to do this and put it on youtube, with a hashtag like #suctionscreen to hopefully get more owners, operators, and mechanics to become aware of this requirement, and to check their suction screen.

You mean something like this?

https://www.kitplanes.com/firewall-forward-the-oil-change/

Admittedly though, we did the suction screen on an engine on a test stand because we couldn’t get both hands and a camera into the actual spot on the aircraft and show the job well. I agree that with an actual engine mount and engine control brackets in place, the simple job can add a few minutes of puzzled frustration as you can see what need to be done, but can’t figure out how to get your hands in to do it. Just stick with it, and you’ll get it!

Paul
 
You mean something like this?

https://www.kitplanes.com/firewall-forward-the-oil-change/

Admittedly though, we did the suction screen on an engine on a test stand because we couldn’t get both hands and a camera into the actual spot on the aircraft and show the job well. I agree that with an actual engine mount and engine control brackets in place, the simple job can add a few minutes of puzzled frustration as you can see what need to be done, but can’t figure out how to get your hands in to do it. Just stick with it, and you’ll get it!

Paul

A few minutes? Not on an RV-10 with Barrett CAI...more like hours!
 
You mean something like this?

https://www.kitplanes.com/firewall-forward-the-oil-change/

Admittedly though, we did the suction screen on an engine on a test stand because we couldn’t get both hands and a camera into the actual spot on the aircraft and show the job well. I agree that with an actual engine mount and engine control brackets in place, the simple job can add a few minutes of puzzled frustration as you can see what need to be done, but can’t figure out how to get your hands in to do it. Just stick with it, and you’ll get it!

Paul

Paul that video series is awesome man, couldn't wait for the first one to come out. Love watching stuff like that.
 
If my fingers were two inches longer and wrists about an inch smaller it would have been a piece of cake.
 
You mean something like this?

https://www.kitplanes.com/firewall-forward-the-oil-change/

Admittedly though, we did the suction screen on an engine on a test stand because we couldn’t get both hands and a camera into the actual spot on the aircraft and show the job well. I agree that with an actual engine mount and engine control brackets in place, the simple job can add a few minutes of puzzled frustration as you can see what need to be done, but can’t figure out how to get your hands in to do it. Just stick with it, and you’ll get it!

Paul
That's awesome, Paul! I'm very impressed with your ability to predict my wishes even before I think of them! :D
 
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