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Lycoming IO540 quit during landing

Tom Delaney

Well Known Member
I would appreciate some input on an engine issue. RV-10 IO-540. Upon landing the engine quit during rollout and fuel was seen underneath the engine cowling. Removal of the cowling found the forward airbox smelling of fuel along with some residual fuel that had not drained from the holes in the bottom of the FAB. Remainder of the engine was dry. Just wondering what to look for. Engine apparently flooded but not sure why it occurred. Plane had just finished a 1.5 cross country flight. 460 hours and Savvy analysis data did not show anything out of the ordinary that I could see. Have not experienced previous fuel system issues.

SavvyAnalysis link for the flight:
https://apps.savvyaviation.com/flights/5428238/4670f904-788a-438e-aaf3-b5968d2c615b
 
I was wondering if the fuel system is Injection or Carb.?
Also I am sure you know, three items needed, compression, fuel and spark. either of these out of line it will not run correctly. I believe you think it is fuel. It could be, extra fuel produced after engine quit by electric fuel pump, it was still being pumped but not burned.
I am only thinking out loud, you know your situation better than I.
My thoughts are only possibilities, I am sure someone will expand further, and have the real answer.
 
As Dave said, if you have boost pump on for landing, mixture rich, the boost pump will pump gas into the induction manifold after the engine stopped turning - same as if you over-primed prior to start. Don't know if this is a symptom or a result of the engine stoppage.
 
The fuel pressure plot shows that your fuel pressure dropped to 3 psi when you touched down. Of course the fuel injected engine could not continue running at that low pressure. Do you have an electric boost pump and did you turn it on when you entered the circuit to land. The FP plot doesn't seems to indicate that any boost pump was activated.

At any rate, with or without boost, the FP should never drop to that low level when the engine is running. So there's a fundamental problem there.

It goes without saying that having an engine quit at low power is a very dangerous scenario.

I see you didn't build the aircraft. I think you should get an A&P to check this out rather than trying to troubleshoot it yourself through VansAirforce. Needless to say I wouldn't be flying the plane again until the engine was properly checked out by someone competent.
 
More data is needed, but the one time I was associated with a similar problem it was tracked down to air coming in the fuel line. On that engine the air leak was the fuel pump seals leaking (non Lycoming engine). The engine would run after landing if the boost pump was on. Turn the boost pump off and the engine died. Residual fuel was also present. In other words:
- Engine running no fuel leaking out, but air leaking in the fuel line. Engine not happy.
- Engine not running fuel leaking out until the fuel lines drained.

Carl
 
As others said, big red flag here. This plane is grounded (my 0.02)!

Note that at touchdown the fuel pressure dropped, recovered - twice. Also note the glitch at 45:27, an unexplained drop in fuel pressure.

Don at Airflow Performance would be my go-to. If you can't find a loose fitting, cracked fitting, leaking fuel pump or something... the servo needs to come off and go to Don for IRAN.

Dumb question... any aluminum AN fittings in the FWF fuel lines?

Check for a 'flapper' in all the fuel hoses.

You got lucky. The plane is talking to you. Listen to it.

Read this: https://vansairforce.net/community/archive/index.php/t-181077.html
 
There's another problem here... at 10:00 the takeoff commences. Prior to that the FP was 28 psi. As the power comes up the pressure drops (down to 22) the recovers somewhat. This tells me that there is a restriction in the lines. Or, we're dumping fuel, look at the fuel flow - 25 gph - momentarily. There should be no appreciable drop in fuel pressure. And especially that belch down to 22 psi, which then recovers to 24.

A second suggestion would be to enroll in Savvy Q&A. I suspect they'll have two or three things for you to check as soon as they look at this.
 
From my read of your data, FP is pretty normal all the way until you drop from idle to shut off. As mentioned, the raw fuel in the air box can be from factors other then the one that caused the un commanded shutdown. Boost pump on with mixture other than ICO and the engine not spinning = raw fuel in the FAB. I assume that boost pump was on, as it is pretty much SOP in the pattern.

I would start with idle mixture. If it is a bit fat (i.e. too rich), the most likely time for it to create problems is a quick pull to idle after a long run when things are quite hot and it don't like the richer mixture.

because your data stream is so long, we don't have a lot of resolution at the point of failure. Would be better to look at the 1 second interval raw data and see exactly what is happening when the RPM goes from 800 to 0. Look at FP and other parameters in the few seconds preceding that moment. Look for trends data as well in the several seconds leading up to that moment. Detective work here should net some clues as to what may have caused this.

Larry
 
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Do you have PMAGs for ignition?

The reason I ask is my experience during a bumpy Phase 1 flight, where my hand inadvertently bumped off my PMAG switch-breakers (now guarded). The engine ran fine until round-out and touchdown, when RPM dropped below the self-powered level and shut off...then tower asked if I needed assistance to get off the runway.
 
My .02

Looks to me like the ignition(s) were turned off either on purpose or by accident about 01:19:00 (See rising MAP, Decreases in RPM, Fuel Pressure, Fuel Flow).

Subsequent attempted unsuccessful restarts flooded the engine.

At 1:19:18 restart of engine attempted - Note RPM Increase, Fuel Pressure Increase, Fuel Flow Increase, MAP decrease, Volts decrease -- RPM never makes it above 200RPM.

At 1:19:22 another restart attempted

At 1:20:10 another restart of engine attempted - Note increase in RPM, FP, FF, Oil Pressure, MAP decrease, Volt decrease.

At 1:20:18 another restart attempted

At 1:20:27 another restart attempted
 
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Gentlemen, quick reply due to other commitments.

I really appreciate all the input. Plane is grounded and help is being scheduled. Ground run today was absolutely perfect so no smoking gun found there.

Brian, my partner is emphatic that the ignitions were not turned off but that the engine just suddenly stopped. He then tried several starts as you indicated. Wouldn’t we see the same data if the engine just quit or if the ignitions were turned off? Is there anything in the data to definitively say one way or the other that we are missing?

Thanks again and I will answer more questions later and post any findings to help someone in the future.
 
Details

Tom,

As stated elsewhere, you need Compression/Fuel/Spark (or Air/Fuel/Fire) and from what I can see in the data suggests no spark (Fuel is present in ample amounts, Air also...)

What controls the ignitions on this aircraft - A key-switch (L/R/BOTH/START) style, Toggle/Bat switches? What kind of ignitions are they? (Magnetos, Emag/Pmag, etc.)

I've looked at all the available parameters and don't see one that's directly representative of ignition health...unless I'm missing something.

B
 
Brian,

Switches are toggle: master, Slick magneto and emag (SDS CPI)

Dave,

Didn’t have time to download but our eyes were glued to the engine screen and all looked proper although the fuel pressure does bounce +/- 1 psi.

I will download and provide a link from the ground run, hopefully tomorrow.

Thanks again
 
Observations...

Tom,

As an aside, the Flap Position sensor isn't connected/working or both. Also, whatever is connected to EarthX Input isn't "happy" - If it's an EarthX battery, it's showing a problem - refer to the battery docs. EGT #4 probe connections are bad and/or probe is failing...but that's for another day...

Maybe Ross can provide a means to extract SDS data if none are immediately obvious.
 
It’s an RV10 - my money is on bad pipe flares/ connections at the fuel tap. It happened to me with a customers new 10 just before first flight. Flares were bad on the brakes lines too - scary stuff.
 
More observations...

Zoom in a bit more on EGT and other data at the 01:18:52 mark. Note the shape of the curve for the EGT data -- The fire was put out at this point...

Fuel Flow, Fuel Pressure, RPM, MAP, Oil Pressure are consistent with a propeller windmilling but no combustion.

Propeller stopped turning at 01:19:10, but ground and airspeed were still above 30. Pilot attempted to restart the aircraft while it was still rolling.
 
I'm very curious how RPM is measured on this instrumentation. If it is from the P-lead of the bendix mag, then turning off the ignition - should have made the data go to zero rpm. On the other hand maybe it's a sensor off the tach drive...

Also interesting, the fuel flow went to 5 gph ON CRANKING, but it never went that high at the initial idle and taxi. Tends to indicate improper procedure for hot engine restart. Or some other problem.

Does this system have a fuel purge valve?
 
Zoom in a bit more on EGT and other data at the 01:18:52 mark. Note the shape of the curve for the EGT data -- The fire was put out at this point...

Fuel Flow, Fuel Pressure, RPM, MAP, Oil Pressure are consistent with a propeller windmilling but no combustion.

Propeller stopped turning at 01:19:10, but ground and airspeed were still above 30. Pilot attempted to restart the aircraft while it was still rolling.

Impressive observations/analysis. It certainly does look like combustion ceased at 1:18:52. Fuel pressure dropped as RPM decreased, consistent with not having used the boost pump. Fuel flow then plummeted to zero (consistent with the fuel flow divider cutting off fuel flow) at 1:19:14. Restart attempts brought the fuel pressure and fuel flow back up, but without EGT (no combustion).

Candidate causes for combustion ceasing might include:
- Both ignitions (mag and electronic) quit simultaneously. Seems unlikely.
- Vapor lock - But OAT was 37 degrees. And CHTs are not high. Was fuel 100LL, or auto gas?
 
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Mag Check Drop

Zooming in on around 08:53 - looks like a mag check. Rev up to 1800 rpm. Drops to 1517 and then up, and drop to 1425. So over 250 rpm mag drops. That's way too much.

I'd also like to see a panel photo to see if the mag switches are someplace likely to get bumped. Agree with prior post that it looks like either the ignition failed first (and then the fuel pressure dropped), or it's a mixture issue, although there's no significant EGT change to support that. There is a glitch in the #1 EGT at 1:18:43, just before the fire goes out. From the rpm it looks like the throttle is being pulled back - but oddly the MAP doesn't increase much as the rpm drops from 1700 to 1440, just prior to the EGT cliff.
 
Agree - not fuel related. It is Ignition.

Zoom in a bit more on EGT and other data at the 01:18:52 mark. Note the shape of the curve for the EGT data -- The fire was put out at this point...

Fuel Flow, Fuel Pressure, RPM, MAP, Oil Pressure are consistent with a propeller windmilling but no combustion.

Propeller stopped turning at 01:19:10, but ground and airspeed were still above 30. Pilot attempted to restart the aircraft while it was still rolling.

+1 ignition off at 1:18:52. RPM, FF and Pressure dropped in concert as a result. All other symptoms are generated from this point, including dripping fuel.

Now the question is why the ignition ceased at 1400 RPM. Bad wiring, fat fingers, overheated electronics - - - what ever.
 
Zooming in on around 08:53 - looks like a mag check. Rev up to 1800 rpm. Drops to 1517 and then up, and drop to 1425. So over 250 rpm mag drops. That's way too much.

For a Magneto check -- yes, but not for prop cycling -- note the oil pressure and MAP changes coincident with the large RPM drops at 00:08:53, 00:08:57, and lastly at 00:09:02.

The Magneto/Ignition Checks are done at 00:08:43 through 00:08:51...

OP indicates that the ignition system is magneto & SDS CPI. I would expect 0 RPM drop when turning off the magneto and ~75 - 100 when turning off the SDS CPI.
 
More Information

For those interested the link below is the ground run the day following the engine stoppage.
Some notes:
01:50 checking idle rpm prior to the engine being fully warm. Initially thought that the idle rpm may be set too low.
02:00 Engine shut down to discuss the low idle rpm.
09:32 idle rpm check with engine warm. Around 700 rpm is what we usually see.
14:05 mag check. CPI off/ Slick on
14:55 mag check. Slick off/CPI on

https://apps.savvyaviation.com/flights/5431050/449df017-ccce-4f9a-b671-59954c32fdcf
 
For those interested the link below is the ground run the day following the engine stoppage.
Some notes:
01:50 checking idle rpm prior to the engine being fully warm. Initially thought that the idle rpm may be set too low.
02:00 Engine shut down to discuss the low idle rpm.
09:32 idle rpm check with engine warm. Around 700 rpm is what we usually see.
14:05 mag check. CPI off/ Slick on
14:55 mag check. Slick off/CPI on

https://apps.savvyaviation.com/flights/5431050/449df017-ccce-4f9a-b671-59954c32fdcf

OK, puzzled. The mag drop running on just the Slick (not renowed for being a 'hot' mag) is about 75 rpm. The drop running on just the CPI is about 130 rpm. My rule for max drop is 125 rpm. Now, I don't know the CPI system at all (I've got a Lightspeed and a Bendix mag), but the usual experience is that the electronic ignitions give a great spark, and more importantly, provide part throttle ignition advance, so at mag check throttle settings you are getting more advance on the electronic than on the mag. As a result, the typical result is little or no mag drop when you turn off the conventional mag - and considerable drop when you turn of the electronic system. On this engine, it's the opposite.

I believe I triple checked your note on which mag was on/off in which order!

I'll leave it to folks who know the CPI to chime in with why this might be.
 
Quite a few interesting and intelligent responses on this thread. The idle mixture questions was answered with an idle RPM rather than a RPM roll at idle cut off. But that's okay as everything seems to be pointing at an ignition problem.

So good catch on the mag drop of mag vs. EI system. Could the leads be wrong? We check P-leads at every condition or annual and find a good many aircraft (15 to 20 percent est.) with swapped L & R P-lead connections. In fact when somebody comes in with a mag problem and they pronounce it is either L or R our first test is the P lead connections to make sure we are working on the correct side. So the customer thought L was R or vice versa because the leads were attached on the wrong terminals. Trust somebody's telling you it's L or R and you can find yourself running down a rabbit hole. It is mind boggling to me to get a new to us aircraft in for maintenance that has gone through years of inspections with the P-leads swapped. And then that begs the question what's the deal with a single impulse coupling if the switch is grounding it during start?

Isn't it great having electronic engine data and the above group of smart technical types to analyze it?
 
OK, puzzled. The mag drop running on just the Slick (not renowed for being a 'hot' mag) is about 75 rpm. The drop running on just the CPI is about 130 rpm. My rule for max drop is 125 rpm. Now, I don't know the CPI system at all (I've got a Lightspeed and a Bendix mag), but the usual experience is that the electronic ignitions give a great spark, and more importantly, provide part throttle ignition advance, so at mag check throttle settings you are getting more advance on the electronic than on the mag. As a result, the typical result is little or no mag drop when you turn off the conventional mag - and considerable drop when you turn of the electronic system. On this engine, it's the opposite.

I believe I triple checked your note on which mag was on/off in which order!

I'll leave it to folks who know the CPI to chime in with why this might be.

First, the 125 limit is based upon two mags with fixed timing. RPM drop on mag testing is all about advance, not spark strength. With two plugs firing at 25* BTDC will provide more power and RPM than one plug firing. When the RPMs drops are consistent across both sides, you can assume each has a very similar advance. When they are different, you can assume the timing is different. The greater the RPM drop, the greater advance the dropped mag had. This is a general guideline, as the top and bottom plugs have slight difference in flame front travel.

Larry
 
First, the 125 limit is based upon two mags with fixed timing. RPM drop on mag testing is all about advance, not spark strength. With two plugs firing at 25* BTDC will provide more power and RPM than one plug firing. When the RPMs drops are consistent across both sides, you can assume each has a very similar advance. When they are different, you can assume the timing is different. The greater the RPM drop, the greater advance the dropped mag had. This is a general guideline, as the top and bottom plugs have slight difference in flame front travel.

Larry

Or you have misfire, bad plug, bad wire, etc. I see too many people on this forum that just blow off large mag drops as some sort of normal. There was a poster some time back getting over 200 rpm drop - on both mags - and was still flying the plane.

You also didn't address my main point - why is the drop higher in the opposite direction than we'd expect? Is this electronic mag running with no vacuum advance?
 
Correction

Sorry fellas, I mislead you concerning the order of the mag check. The slick had the largest drop and the electronic had the 75 rpm drop. My apologies.

The six switches are:
Top L-R, master, alternator and oil cooler servo.
Bottom L-R, magneto, electronic and start

I spoke with Ross of SDS who was very helpful. Among other things he stated the normal range of mag drop for the CPI is up to 100 rpm.

The slick mag is off the plane and being inspected. Should have that back in place Saturday. My magneto guy is looking for replacement kit (MK605) for this mag, Champion model #6393. Unfortunately the kit has been on back order for some time. Anyone know a source for this kit?
 
Wow... Just.. Wow..

After reading through the particulars of this thread, it occurs to me that this is a PERFECT example of just how lucky we are to have the Vans Air Force community. I don't know about you guys, but I'm giving Doug a "Bonus" in this year's annual dues pledge. I'd urge anyone/everyone to do the same.

Doug,

This, right here, is why you mean so much to us all. Thanks for all you do to make this community work. It's probably saved a few lives along the way too!
 
You bet Mike!

What a learning experience for me. That is why I started the thread. This website has helped in hundreds of ways and I thought we could all possibly learn from my experience. Sent in my donation just last week.
 
Or you have misfire, bad plug, bad wire, etc. I see too many people on this forum that just blow off large mag drops as some sort of normal. There was a poster some time back getting over 200 rpm drop - on both mags - and was still flying the plane.

?

No. If you have a plug not firing, That cylinder will simply not have combustion on one of the ignition sides; Pretty tough to not notice a 4 cyl engine running on 3 cylinders; They get pretty rough. RPM drop isn't necessary to identify a dead plug, though it will show a serious RPM drop. EGT also drops like a stone.

FYI, I did NOT blow off concern with large mag drops. I just explained the reasoning for why they can be mismatched, to help you find the issue. teaches me a lesson for sure.
 
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You also didn't address my main point - why is the drop higher in the opposite direction than we'd expect? Is this electronic mag running with no vacuum advance?

Can't address that; not enough info. It is opposite of what is expected. I only identified that it was a timing mismatch. EI's are usually more advanced than mags and will show a larger drop when running on the mag only. However, the drop imbalance points to timing differences between ignitions.
 
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