Sudden Engine Failure

[speedbrakes22]

Hello All

We were 2-3 minutes from taking off in our Mooney M20E when the engine suddenly quit. It recovered briefly when the throttle was pulled back halfway, but then quit for good. Successful off-field landing; no injuries; no damage.

 

Full tanks, both sumped 45 minutes after fueling. Full-power runup before takeoff revealed no anomalies. Fuel selector on left tank; boost pump on throughout the episode. Mixture rich. Field elevation 2,000 feet. Altitude when engine failed about 3,500 feet.

 

Post-incident inspection shows good fuel flow from both tanks, good operation of fuel selector valve. Hoses from pump to servo secure, hose from servo to injection distributor secure. Only defect is missing full-rich stop on fuel injection servo. We’re having the servo rebuilt, but we’re not confident that’s the problem. Engine ran strong during prior 10hr X/C. 

 

Any ideas?

[gjkirsch]

 I don't remember the specifics of that engine.  The basics of fuel, air, spark would lead one would to think it is around fuel delivery to the engine that was interrupted based on your description.  Anything else would most likely have shown itself in a rough running engine or an engine loosing power rather than just dying.  Could the tank vent or fuel pick up line in the tank become blocked?

[yvesg]

Did you notice the fuel pressure indication when the engine quit?

Yves

[MooneyBob]

Glad you made it safely down.

[speedbrakes22]

It's the IO-360 A1A.  We will check the tank vents. Post incident test demonstrates good fuel flow to the servo.

 

Not sure on pressure indication being we had very little time to set up forced landing. 

[KSMooniac]

Welcome to Mooneyspace and congrats on handling the emergency correctly and getting the perfect outcome.

 

Do you have an engine monitor with data logging capability?  If so, downloading the data might be helpful with the investigation.

 

Fuel issues sound like a good candidate.  You might look inside the gascolator and see if there is any debris in the screen.  Consider doing a baby food jar fuel test with each of the fuel injection lines as well.  

[orionflt]

if my memory serves me correctly you have two individual mags not a dual mag set up so i would check your accessory drive train to ensure that you did not have a gear failure. if you had a dual mag set up i would look there first, as for the rest of the ignition system any individual item failure should not cause the complete loss of the engine. you may want to check the ignition switch but i doubt that is the issue (they usually fail hot). 

 

brian

[speedbrakes22]

Thanks for the welcoming! 

 

No engine monitor. 

 

The A&P checked the gascolator, no debris found. We will try the food jar test. 

[MooneyBob]

What's the food jar test. Share please. Thanks.

[KSMooniac]

Food jar test involves placing four jars at each of the four fuel injection lines and running the boost pump to check for even flow to each cylinder.  Can be done with and without the injectors connected.  In this case, though, since there was a complete loss of power it is unlikely that just one cylinder has a restriction, but perhaps something failed in the system and this is another way to check fuel flow.

 

The -A1A engine has two separate mags.  I don't know enough about the accessory drive system to know if a single gear failure could stop both of them or not.  Worth checking that as well.

[N601RX]

The crank gear bolt and drive dowel is the common link to all the accessories.  If it shears then you loose the cam timing, oil pump,  both mags, fuel pump and vac pump.  There was a local plane went down here because the crank bolt appeared to be left out at overhaul and after a few hundred hrs the dowel broke. No traces of the bolt or locking tab were found during the post ditching tear down.

[Marauder]

I would also check some of the usual suspects; throttle & mixture cables working properly & nothing amiss on the ignition switch.

It does sound fuel related because of your comment of pulling back the throttle had a momentary effect.

[neilpilot]

In 2011 I experienced a similar incident in a 64E.  Did the usual checks, and could not find an obvious cause.  Over a 12 month period I had both mags and the fuel injection serviced.  No anomalies were reported.  

 

Then in July 2012 the engine stopped again, resulting in an off-field landing.  The aircraft was totaled, and a few months later I participated in the NTSB investigatory tear down.   Everything they looked at (fuel, mechanical fuel pump, injectors, engine compression, mags, etc) looked good.  They decided to send the mags and RSA unit out for inspection.  The NTSB later determined that a broken piece of an O-ring in the servo blocked normal fuel delivery.  The NTSB investigator reported that "The fragment and the missing portion of the o-ring are similar in size. No other o-rings within the servo appeared to be damaged. I believe that it is likely the fragment came from the idle valve assembly."  

 

PS - I now fly an O-360, eliminating that pesky fuel injection unit

[Piloto]

I had a similar event on my old M20C, luckily the runway was 10,000 feet long and was able to land ahead. The cause was water in the tanks. I drained the tanks before flight and found no water. After the engine stoppage I was able to restart on the taxiway and taxi to the ramp. Suspecting water on the tanks I drained the tanks again but no water. Getting suspicious I removed the tanks drain valves and sure enough there was plenty of water. 

 

The factory drain valve drain holes are at the very bottom of the valve next to the hex nut head (below the thread). To drain the fuel through these holes the drain mounting nut plate has holes through at the very bottom in contact with the skin. When these holes get plugged with debris or sealant the fuel is drained from the very top of the valve stem. This causes water to accumulate below the stem top but above the fuel pick up in acceleration or climb attitude. During normal taxing or run up water will not get to the fuel pick up on the rear of the tank but it will during acceleration or climb. 

 

To prevent the problem from happening again I replaced the drain valves with the MDI F-391-72, same ones used on the long range tanks. The F-391-72 has the drain holes above the thread and above the valve mounting plate. So the holes could not be blocked by sealant or debris.

 

To make sure it does not happens to you remove the drain valves on occasions to check for water. But if the holes are blocked you will not be able to drain the water that the last fuel truck put on your tanks, unless you remove the valve.

 

The annoying part of this problem is that the full power run up will not show any indication. If suspecting this on climb switch tanks. Or switch drain valves.

 

José

[speedbrakes22]

Great ideas, comments and suggestions. 

 

We are going to start with overhauling the fuel servo. It pasted bench test inspection but still weary about it because of its age.  We have checked all the parts to the fuel system from the tanks to the injectors and found no problems. 

[DaV8or]

Congratulations on the successful conclusion to a serious emergency! Many, many others have not done so well in this scenario. Do not take this as any sort of criticism of your handling of the event, my intent is just curiosity as to why your engine quit.  You did the job perfectly and I could not have done better.

 

While you were gliding, did you do any engine diagnostics? Boost pump on? Switch tanks? Cycle the mags? Move the throttle and mixture in and out? Did the engine ever run again once on the ground?

 

If it were the accessory gear failure, a quick timing check should tell you that. Water in the fuel enough to stop the engine should have been obvious when you trained the tanks. Have you inspected the fuel selector internally? What about vapor lock? Before take off, was this a hot start and had you been flying the plane previously? How's the condition of your ram air boot? They are friable when old and if some of that breaks off, it can block the impact tubes on the fuel servo, or so I've been told.

 

Again, congratulations on handling the forced landing!

[romair]

Piloto - I may not be understanding exactly what you are describing - but it seems that the valves you have on, have the drain holes higher than the factory ones. While indeed they would not get debris, aren't you draining from a point higher in the tank? You can then have a layer of water at the bottom, yet you would not know since the drain hole is above it.

Stefan

[carusoam]

He says...

The lower holes are causing a different type of challenge. A lesser known one, that may lead to an undetectable blockage...

He is the most knowledgable guy on that particular subject.

Worth waiting for additional clarification, if needed!

Best regards,

-a-

[Yetti]

You might also go sump the fuel storage at the last place you filled up if at all possible.

[speedbrakes22]

Congratulations on the successful conclusion to a serious emergency! Many, many others have not done so well in this scenario. Do not take this as any sort of criticism of your handling of the event, my intent is just curiosity as to why your engine quit.  You did the job perfectly and I could not have done better.

 

While you were gliding, did you do any engine diagnostics? Boost pump on? Switch tanks? Cycle the mags? Move the throttle and mixture in and out? Did the engine ever run again once on the ground?

 

If it were the accessory gear failure, a quick timing check should tell you that. Water in the fuel enough to stop the engine should have been obvious when you trained the tanks. Have you inspected the fuel selector internally? What about vapor lock? Before take off, was this a hot start and had you been flying the plane previously? How's the condition of your ram air boot? They are friable when old and if some of that breaks off, it can block the impact tubes on the fuel servo, or so I've been told.

 

Again, congratulations on handling the forced landing!

Thanks, all the right cards fell into play for a successful outcome.  We did have a few seconds to run diagnostics. The boost pump was on. Didn't have time to switch tanks. Didn't think to cycle the mags just verified they were on both.  Did cycle the throttle and the engine sputtered momentarily then quit. The engine did run the following day, but wouldn't start again cold or hot.  Vapor lock is a strong possibility since it was hot. Will inspect the ram air boot. 

 

Thanks 

[rockydoc]

Congrats on getting down safely.  Whatever you did was right.  Retrospectively, it seems the first thing to do would be to turn on the fuel pump (which was probably already turned on for the TO) and determine if there is fuel pressure. Then if there is correct fuel pressure, switch tanks to see if the problem follows to the other tank.  I had a similar issue once and the problem turned out being a SMALL piece of fuel tank sealant that was intermittently clogging the fuel line where it exited the tank itself.  Once again...nice job.  Should I be so fortunate when it happens to me.

[Piloto]

Stefan

 

The F-391-72 drain hole height from the tank bottom is only 1/4". Not enough to accumulate any water. In fact the stiffeners in the tank will trap more water.

 

One problem with the original drain valves (F-391-53S) is that when a mechanic put sealant on the thread to fix a fuel stain around them. The sealant will squeeze down as you screw the valve in plugging the drain holes. It may fix the stain problem but now the drain valve is draining from the stem top.  

 

The trapped water will shift toward the back during takeoff where the fuel pick up is located.

 

Another item to keep in mind is the fuel cap O-rings. Even if you have new O-rings you may have water leaks around the cap. To verify no leakage put a  little bit of spray soap like SD-20 around the filler cap perimeter. Then blow air (by mouth only) through the tank vent to build pressure. Check for bubbles around the cap perimeter and center shaft. If you see bubbles check the cap lever adjustment nut. Also check for corrosion on the filler hole cap adapter ring. Caps leaks are not obvious because there is no fuel pressure on them to stain the wing.

 

José

[mooniacX]

Hi Speedbrakes22

Just wondering if you ever found the problem?

[speedbrakes22]

Overhauled the servo and fuel flow divider. Checked and rechecked everything else and followed up on all suggestions from this thread and elsewhere. Went to pick the airplane and fly it back today, after 22 hours of driving. Ready to fly.. Put it through its paces on the ground 20+ minutes; purred like a Porsche. Shut it down; waited a half hour. Started right up; did several runups, some at full power; no problems.

 

Took off stayed glued to vicinity of the airport for 45 minutes at 4,000 feet AGL; filipped tanks several times; toggled fueltboost pump on and off; various airspeeds and power settings; still Porsche-like. Felt like all was good and headed east. 

 

Then, without warning, and without any further adjustment in throttle mixture or prop, engine choked for 10 plus seconds and was about to quit. Enough altitude (4,000 AGL) to catch fuel pressure approacing zero; and fuel flow meter extremely low. Boost pump on, switched tanks and jockeyed throttle and mixture.  Engine came back to life on other tank. Returned to overhead the airport; spent another 10 minutes trying to get the problem to repeat itself. No luck. Everything ran strong on both tanks.

 

It's a wonderful airplane except for its engine quitting periodically, which significant impairs flight plans.

 

Everyone is stumped. Any further ideas.

 

. 

[carusoam]

So if I understand correctly...

1) Boost pump and tank switch brings FF back to normal...

2) we covered the usual fuel blockage and fuel leakage areas...

3) pump operations must be next

4) did we cover blocked tank vents?

Thinking out loud,

-a-