Engine failure in flight Jan.31

[MikeOH]

18 minutes ago, DCarlton said:

We're about to replace the fuel line on my F.  I was already concerned because the upper end behind the engine is so difficult to access.  Now I'm even more worried.  Hopefully the mechanic has some trick tools to allow him to get a good torque on the fitting.  I'm wondering now if it's better to leave well enough alone and not create a self inflicted problem.  The point of the exercise was to address the outstanding SB.  

I am NOT an A&P so this is just my opinion: I'd be far more worried about a maintenance induced failure brought about by messing with that inaccessible fitting, than a leak suddenly developing after many years of faithful leak-free operation.  Sure, some things wear out and need to be inspected/replaced on a periodic basis; I don't think a fuel fitting falls into that category.  Again, IMHO.

Just check the lower fitting angle per the S/B and call it a day.

[DXB]

8 hours ago, PT20J said:

Nice job handling the emergency. 5500 feet isn't all that high -- probably less AGL -- and you made the Mayday call, found a landing spot and did all the troubleshooting you could.

The B nut on the fuel pump was probably loose at takeoff and vibration caused it to become a lot looser in flight. Since it was on the output of the fuel pump it could easily reduce fuel flow. The pump will attempt to maintain fuel pressure by increasing the flow, but most is going out the leak and not to the servo. The 3-6 gph you saw at cruise throttle probably drove the mixture too far LOP for combustion.

I had that same B nut come loose on my 1978 J. Fortunately, it was only slightly loose and I noticed it when returning to the plane after a short stop because gas was dripping on the nose tire. I was lucky because I had planned a long flight with my wife the next day over inhospitable terrain.  I tightened the fitting and never had another problem. I would expect that yours will be fine.

I'm a little confused by which fuel line came loose at which fitting.  It sounded like it may have been the one from the firewall to the engine driven pump since it had a firesleeve on it and also possibly had been messed with at tecent engine reinstall?   On the vintage birds the line from the boost pump behind the firewall is distinct and wouldn't be touched. I don't know anything about the J's fuel system though.

[PT20J]

54 minutes ago, DCarlton said:

We're about to replace the fuel line on my F.  I was already concerned because the upper end behind the engine is so difficult to access.  Now I'm even more worried.  Hopefully the mechanic has some trick tools to allow him to get a good torque on the fitting.  I'm wondering now if it's better to leave well enough alone and not create a self inflicted problem.  The point of the exercise was to address the outstanding SB.  

It's not really an issue. All it takes is a stubby wrench to torque the B nut. But, it's not a bad idea to check all the B nuts to make sure they are tight and I now put torque seal on them to make it obvious if any have loosened (they never have).

[Slick Nick]

When I originally saw this on Facebook the day after it happened, I replied to one of your comments there, but I’ll reiterate here: great job getting it down in one piece. I’ve spent many many hours over that neck of the woods and I know the terrain out there is less than friendly. You were fortunate to find that road where you did, not just for the hard surface to land on, but for the link to civilization. Landing safely is no good if you can’t avoid exposure. 

I understand the reluctance in wanting to fly it after that, I think once you have a good mechanic go over it with a fine tooth comb, it will be good to go as long as they’re sure that they’ve found the cause. 

[Shiroyuki]

1 hour ago, Slick Nick said:

When I originally saw this on Facebook the day after it happened, I replied to one of your comments there, but I’ll reiterate here: great job getting it down in one piece. I’ve spent many many hours over that neck of the woods and I know the terrain out there is less than friendly. You were fortunate to find that road where you did, not just for the hard surface to land on, but for the link to civilization. Landing safely is no good if you can’t avoid exposure. 

I understand the reluctance in wanting to fly it after that, I think once you have a good mechanic go over it with a fine tooth comb, it will be good to go as long as they’re sure that they’ve found the cause. 

Thank you. I didn’t realize that was you in the comment. I was flying pretty much two days after at my airline, and jumped back in flying it to Toronto myself. Didn’t flew it out of the highway because I was in Montreal for sim.

I’m now definitely more hesitant about flying single engine piston in remote area now. But this is where I live, for now, unless I get a twin, this is unavoidable. I guess I just hit some bad luck, cataching the 1 in 5500 hour incident early. Or made a bad decision buying this particular M20.

I had proper equipment for the environments, from shelter to fire to saws and heat pack, rations, sat phone etc. But you are absolutely correct that I don’t want to end up in the woods here. What scares me more is during the months of thawing and freezing, before ice is thick enough to land on, if I end up in the water, I’d freeze real quick and trapped in thin ice. Crashing into wood around here, with rocky terrain, doesn’t sounds like a very good idea either…

I’m definitely going to keep flying this plane for sure, but now I’m definitely going to exercise I follow roads more closely… I thought this would be my forever plane, as it does everything I want… But now I want two engines… or maybe a parachute…

[Shiroyuki]

4 hours ago, DXB said:

First and formost terrific job handling this!!  Combined with a little luck, your skills let you walk away from a dire situation, and the aircraft basically being fine is a nice bonus. As far as I can tell, the cause seemed likely to have been a transient obstruction like ice in a distal portion of the fuel system.  The leak discovered at the fuel hose attaching to the engine side of the firewall (proximal to any such obstruction) is serious but seems like a red herring here since you had good fuel pressure measured distal to it before and after the engine quit. I only wonder if you have a data logging engine monitor to help sort the events out a little better.  Your engine failure catches my attention because I've previously experienced two in flight anomalies, documented here on Mooneyspace in separate threads complete with engine monitor data (see below), that I ultimately attributed to small amounts of ice in the fuel system on cold winter days.  Of course my carb'd fuel system is quite different, and my engine didn't quit, but both events did scare me.   

A useful discussion point here might be: what is the best SOP to mitigate risk of ice crystals plugging fuel system components when operating in cold temps? Sumping may not catch such materials, which could have already been present in the fuel when it was pumped at very cold temps.    How cold should it be for one to think about it? What other factors contribute?  I know Avgas itself freezes at <-60-72F or so. I also know one can add up to 1% isopropyl alcohol to fuel.  When should one do this routinely? Does one need a full 1%?  Will that small amount of alcohol dissolve crystals that have already formed?  Does anything need to be done to mix the alcohol in? I find very little written out there on this topic.  

I think that answering these questions might give you the confidence to trust your bird again in the frigid northern latitudes - there's nothing intrinsically unreliable about it.

 

 

Yeah that’s what the float plane guy told me to do. He use alcohol in fuel all the time since he had an engine failure in a Malibu over Lake Superior once… and now he uses it religiously…

[Shiroyuki]

5 hours ago, EricJ said:

Sound like you did all the right things.   Had you been cruising with the ram air open by any chance?    Was there any moisture in the air where you were cruising?   The fuel servo is sensitive to what happens with the ram tubes, and if the ram air is open and there's any moisture in the air I'm guessing it's possible either one or more ram tubes iced over or moisture was ingested into a ram tube and froze inside the servo.   There's all kinds of crazy stuff can happen when then servo isn't happy, including failing (I've been there, too).   It would also explain why everything was fine afterward.   That's just speculation on my part, but it might have been something crazy like that.

Edit:  BTW, nicely done and I'm glad it came out well and you're getting it sorted out.

 

Yes, the ram air was open, it gave me half an inch but that’s still half an inch…. It was a crystal clear day so no moisture whatsoever.

[Shiroyuki]

12 hours ago, PT20J said:

Nice job handling the emergency. 5500 feet isn't all that high -- probably less AGL -- and you made the Mayday call, found a landing spot and did all the troubleshooting you could.

The B nut on the fuel pump was probably loose at takeoff and vibration caused it to become a lot looser in flight. Since it was on the output of the fuel pump it could easily reduce fuel flow. The pump will attempt to maintain fuel pressure by increasing the flow, but most is going out the leak and not to the servo. The 3-6 gph you saw at cruise throttle probably drove the mixture too far LOP for combustion.

I had that same B nut come loose on my 1978 J. Fortunately, it was only slightly loose and I noticed it when returning to the plane after a short stop because gas was dripping on the nose tire. I was lucky because I had planned a long flight with my wife the next day over inhospitable terrain.  I tightened the fitting and never had another problem. I would expect that yours will be fine.

I will inspect those nuts again when I’m picking up my plane again. For the previous flights I did not notice any fluid leak at all, and I was actively looking for traces of oil, since the oil leak was just fixed, so if there is, I wouldn’t miss it.

[LANCECASPER]

On 4/19/2025 at 6:54 PM, Shiroyuki said:

To add, I did sump my tank in Toronto and noticed no water in fuel, and fuel cap o ring is fairly new.

How new? The large black outer o-rings can develop cracks in a year. The blue flourosilicone o-rings are much better.

However it's the internal small o-ring that gets missed on the fuel cap. It's harder to change and you can't see the condition without taking the fuel cap apart. If there is water sitting in the cap and that o-ring is old it will get by there and you will have water in the tank. As me how I know. It only took me once to learn that lesson.

https://www.csobeech.com/fuel-caps.html

 

[DCarlton]

15 hours ago, MikeOH said:

Just check the lower fitting angle per the S/B and call it a day.

My hose is a little too long to reorient the fitting angle IAW the SB without replacing the hose.  Too many interferences.  Although I'm not expert, I think everyone should check that fitting angle; not just Es and Fs.  That fitting could be reoriented on any Mooney when a fuel line is replaced or an engine is overhauled.  Perhaps experienced mechanics know from best practices not to leave a low spot in a fuel line that might trap water; but it's an easy detail to visually check.   Agree though from this post, we're gonna make dang sure we have good torque on that difficult to access nut.  

[Yooper Rocketman]

Years ago, I think on this forum, someone found (the hard way) when they ran one fuel tank dry, they had a small leak in the selector valve that probably pulled an very minor amount of fuel from that tank when selected to the other, but pulled AIR into the fuel system once empty.  The emergency landing with their "non-running" Mooney ended up being benign (no, I don't remember the details......it was probably 25+ years ago).  Although the selector was on the tank with fuel, the engine was ALSO pulling air from the dry tank.  Air has a lot less resistance than fuel, so the engine was pulling mostly air.

What I DO REMEMBER, is that I never ran a tank dry again after hearing that story.

Tom 

 

[M20S Driver]

48 minutes ago, Yooper Rocketman said:

Years ago, I think on this forum, someone found (the hard way) when they ran one fuel tank dry, they had a small leak in the selector valve that probably pulled an very minor amount of fuel from that tank when selected to the other, but pulled AIR into the fuel system once empty.  The emergency landing with their "non-running" Mooney ended up being benign (no, I don't remember the details......it was probably 25+ years ago).  Although the selector was on the tank with fuel, the engine was ALSO pulling air from the dry tank.  Air has a lot less resistance than fuel, so the engine was pulling mostly air.

What I DO REMEMBER, is that I never ran a tank dry again after hearing that story.

Tom 

 

Don Maxwell has also made this point several times on this forum too.  It makes perfect sense to me.  

[Hank]

3 hours ago, Yooper Rocketman said:

Years ago, I think on this forum, someone found (the hard way) when they ran one fuel tank dry, they had a small leak in the selector valve that probably pulled an very minor amount of fuel from that tank when selected to the other, but pulled AIR into the fuel system once empty.  The emergency landing with their "non-running" Mooney ended up being benign (no, I don't remember the details......it was probably 25+ years ago).  Although the selector was on the tank with fuel, the engine was ALSO pulling air from the dry tank.  Air has a lot less resistance than fuel, so the engine was pulling mostly air.

What I DO REMEMBER, is that I never ran a tank dry again after hearing that story.

Tom 

That story is encouragement for proper maintenance of your Mooney.

Below is the Fuel Management section from my Owners Manual, where the procedure is to takeoff and flynfor one hour, then switch tanks and use all fuel from the second tank . . .

I prefer switching every hour, and when pushing range will aim for 2:45 from the first tank to approach dry, but I don't always go to stumble, it depends on how nervous I get while watching the clock and waiting.

But I do like knowing that the 15 gallons i have left on approach is all in the selected tank, and not split between both tanks.

[exM20K]

I will run mine down to the panel Low Fuel annunciator light, just like I did in the 231, as corroborated by the totalizer .  That is in level flight.  The warning comes on early in the descent. I have verified after many of these flights that the warning comes on at 8 gallons remaining.  That is sufficient certainty for me should I need to use that last half hour of fuel.

-dan

[dkkim73]

13 hours ago, LANCECASPER said:

However it's the internal small o-ring that gets missed on the fuel cap. It's harder to change and you can't see the condition without taking the fuel cap apart. If there is water sitting in the cap and that o-ring is old it will get by there and you will have water in the tank. As me how I know. It only took me once to learn that lesson.

@LANCECASPER What kind of O-rings do you use? I think I made an inquiry on the fluorosilicone rings but was told they didn't have the right kind for the 2009 Acclaim. Curious if you ran this question to ground and where you get the rings. 

[LANCECASPER]

Just now, dkkim73 said:

@LANCECASPER What kind of O-rings do you use? I think I made an inquiry on the fluorosilicone rings but was told they didn't have the right kind for the 2009 Acclaim. Curious if you ran this question to ground and where you get the rings. 

I used the blue fluorosilicone ones on my previous Mooneys. The Acclaim uses different fuel caps. 

[Fly Boomer]

9 hours ago, dkkim73 said:

@LANCECASPER What kind of O-rings do you use? I think I made an inquiry on the fluorosilicone rings but was told they didn't have the right kind for the 2009 Acclaim. Curious if you ran this question to ground and where you get the rings. 

I think @OSUAV8TER carries them.

[Pinecone]

Or if they don't make them, he can look into having them made.

[Denis Mexted]

When you are flying with big distances between airports (such as the the Canadian 'outback', or more familiar to me Australian outback, or remote islands in vast oceans) and arriving with minimum reserves, having those reserves in one tank makes sense. I've ran tanks dry on many aircraft, many times. It gives you confidence in the sums, or these days the fuel flow gage and digital readout.

Re this failure, what luck! Your next move should have been to the 'lotto' office and buy a ticket in the big draw. 

By the looks of the pic the skies were clear? 

I haven't had much to do with the Ram Air system on the Mooney. It seems self explanatory. But a friend told me story where he was over hills in the dark and the engine started loosing power. He descended into warmer air and it improved. His theory was although the Ram Air was not being used, the butterfly valve at the front was leaking air. Moist air that was freezing in the throttle body. 

If that be the case wouldn't that happen anytime the Ram Air was used, below the freezing level, and in moist air?

I'm in the camp that the leaking fuel is a red herring also. A bit of ice in the system, fuel pump on and the burning process moves out of the possible burning stoichiometric ratio. 

Just a stab in the dark guess.