G100UL - fuel leak

[Marc_B]

Out of curiosity @donkaye, do you know if your Bravo has any nitrile or Buna N fuel system components or fuel hose assemblies that that aren't Teflon lined?  I haven't a clue and more importantly I'm not entirely sure if that matters or not??

 

The unfortunate issue is that it's well established that G100UL stains paint even with minor spills, drips or even an absorbant mat used for fueling another aircraft (and may damage paint in some cases).  I think that a sizeable apprehension with the fuel isn't how it runs in the engine (so far data shared by GAMI suggests it performs well in that regard and most field reports suggest indistinguishable) but how do we prevent it from "running" anywhere else.  Are nitrile components a real concern?  Because I'm pretty sure there are some in our Mooneys.

The back and forth and speculation comes from the vague G100UL ICA, field reports with a few issues, and Mr. Braly's response: not that you're not going to have issue with nitrile, but rather "you don't need to 'change' anything if you follow 'modern' recommendations."  But at the same time he is very clear in recommending Viton and teflon-lined hoses and very skeptical of wet wings...leaves a lot up to speculation.

Of course it also doesn't help anything that Swift alleges that the aromatic amines in G100UL are unsafe for our fuel system.  Braly/GAMI alleges that ETBE and metals in other fuels are unsafe for our fuel system.  PAFI/EAGLE is taking a long time.  Yet the political pressures that keep this moving seem to escalate.

In all fairness, I don't think this is quite like an avionics discussion...but even then, we have oodles of threads on Avidyne, Dynon, Garmin, choices of autopilots, and "what plays well together and what doesn't."

 

As a final confounder, time off around the holidays also makes it easy to read up, take a story and head WAY down the rabbit hole! 

Here's to a Happy New Year, Don!  Hopefully one full of good Mooney adventures and way more time in the air than on our computers and Mooneyspace!!   (my new years resolution will be to stop posting about this )

[MikeOH]

3 hours ago, donkaye said:

Bottom line to me is if you want the benefits of unleaded fuel with some caveats use it, and if, not, don't.

100% agree.

My angst is that Kalifornia is on a path to take that CHOICE away from me.

[A64Pilot]

Benefits of unleaded fuel are spurious at best, people have been burning car gas for decades, other than the cost difference there doesn’t seem to be any other advantage, but the difference in cost adds up

Over at the C-140 Assn they can show that for a C-85 if run just on car gas that at overhaul time the difference in fuel cost will pay for the overhaul, at least several years ago they could, they way parts have gone crazy maybe not now.

A loose fit air cooled engine that burns oil will trash up its oil from blow-by with or without lead and if you want long engine life you really shouldn’t extend change interval.

That leaves plugs, personally I rarely have to clean mine and when I do it’s no big deal, it’s carbon that has me cleaning them, not lead.

Now this is my belief / opinion but I believe any engine unless it has specially hardened valve seats will experience seat wear and have valve recession if run on unleaded fuel, at least all the cars did when we switched to unleaded car gas anyway.

If you search you can find “experts” saying both, that long ago Lycoming switched to “hardened” seats and can burn unleaded fuel with no issues and others that say they can’t.

Lycoming investigated the valve seat recession of UL94 and I believe said it exist, but isn’t or shouldn’t be from no lead, blaming I believe aromatics in the fuel.

But 100LL with aromatics doesn’t cause valve seat recession, maybe the lead protects the seats?

https://www.lycoming.com/press/lycoming-engines-ul94-valve-seat-recession-investigation-update

[donkaye]

5 hours ago, Marc_B said:

Out of curiosity @donkaye, do you know if your Bravo has any nitrile or Buna N fuel system components or fuel hose assemblies that that aren't Teflon lined?  I haven't a clue and more importantly I'm not entirely sure if that matters or not??

As I mentioned before, I fly airplanes, am not a mechanic, and for better or worse trust the people who designed them.  I have no idea about the materials used in the fuel system.  There are risks in life, and my love of flying means choosing an airplane I think minimizes that risk by a design that has stood the test of time.  Mooney is that airplane.

[exM20K]

1 hour ago, donkaye said:

There are risks in life, and my love of flying means choosing an airplane I think minimizes that risk by a design that has stood the test of time.  Mooney is that airplane.

Amen. And it is the novelty of G100 and any other new fuel that gives this aviation conservative pause as to adopting a radically new fuel. 
-dan

[gabez]

Another data point from my plane (which is not in the shop yet and the paint damage keeps getting worst). In 9/2022 we repositioned the sump drain valve as when (before my time) the aux were installed, the sump were not located at the lower point which allowed for water to accumulate. 

In order to reposition the valve we opened up the aux and resealed the tanks, that was done 9/22 with no leaks until started using G100 approx 12/2024. The material used to seal is attached. I pulled this from my invoices 

 

Hope this adds another data point 

Edited Thursday at 04:51 PM by gabez

[Pinecone]

Did you remove all the old sealant and put in new?  Or did you just patch leaks?

[gabez]

I didn't do anything, my mechanic did it. Only thing I know is that I had no leaks until I have started using G100. 

[Pinecone]

Understand.  But the history of your plane tanks is important to understanding how this happened.

If it was only patching, there are a LOT of years of possibly other patches that are the actual issue.

[MikeOH]

7 hours ago, Pinecone said:

Understand.  But the history of your plane tanks is important to understanding how this happened.

If it was only patching, there are a LOT of years of possibly other patches that are the actual issue.

The ISSUE is if whatever patches, new or old, are MORE affected by G100UL than by 100LL.

[Pinecone]

True.   But so far only one Mooney has been reported with new leaks.

So makes me suspect the sealing history.

[A64Pilot]

9 hours ago, MikeOH said:

The ISSUE is if whatever patches, new or old, are MORE affected by G100UL than by 100LL.

I’ve patched several tanks, every time I patched the materials used were identical to the original sealant.

A patch therefore shouldn’t be any weaker or more susceptible to solvent attack than the rest of the tank, if anything as it’s new sealant it ought to be better?

If a patch worked for a significant time with any fuel, it should work for any fuel if you change fuels?

Every issue with patches I’ve seen were basically from inadequate prep, whether from not digging out enough of the old, or making sure the old was completely clean (I was patching turbine tanks and Jet is oily), or old out of date sealant.

If your sealant is old it may not ever cure correctly, cold temps can cause the same thing, if your mixing from cans it may be prudent to mix a test batch the day before, and keep some from your patch so you can be sure it cures completely.

[A64Pilot]

4 minutes ago, Pinecone said:

True.   But so far only one Mooney has been reported with new leaks.

So makes me suspect the sealing history.

Yes, IF there is a problem, more will pop up, if not then they won’t. I hate to say it but I believe the early adopters are the true testers.

My concern would be with fuel cells, if this stuff softens and swells O-rings, what’s it going to do to bladders?

OK, so it doesn’t short term, what about long term as in years?

I’ve seen swollen O-rings, every one I saw was also softened, so I assume the same here?

I know your not supposed to reuse O-rings, but sometimes you have no choice, those that had swelled up slightly we would put in the freezer, then you could get them to fit the groove and reassemble, but I’m talking only slight swelling, not what I saw in the video.

Edited 20 hours ago by A64Pilot

[GeeBee]

That AOPA Baron except for a bladder leak in a 50 year old patched bladder that leaked at the patch, some before G100UL, seems to being doing just fine. I'm betting it has a lot of nitrile in it too. Now with a new bladder we can watch.

[A64Pilot]

I made a couple of calls, first I called Griggs who has the Mooney fuel cells now, they have no idea at all whether the Gami fuel will have any effect on their cells or not.

Secondly I called Eagle fuel cells who I’ve had past experience with and respect, unfortunately the person who could speak to that issue is out and will return my call.

Mooney fuel cells are made from Neoprene and Nylon, assumption mostly neoprene with nylon reinforcement where necessary.

http://griggsaircraft.com/fabrication/mooney_bladders

I did some looking at what the difference is between nitrile and neoprene, it seems nitrile is much more chemical resistant especially oils and solvents than neoprene

If nitrile is reacting, then it seems neoprene may be worse? Maybe, time will tell.

https://www.casertainc.com/blog/nitrile-vs-neoprene/

Edited 17 hours ago by A64Pilot

[MikeOH]

5 hours ago, GeeBee said:

that leaked at the patch, some before G100UL, seems to being doing just fine. I'm betting it has a lot of nitrile in it too. Now with a new bladder we can watch.

So, what is 'some before G100UL'? If it was just a little while using 100LL, and then a lot AFTER G100UL, that's pretty important!

And, what's your point with "now with a new bladder we can watch?" It's been, what, a month? Or, is your expectation that we all spend the money to buy new bladders, new paint, new Viton O-rings...only, then are we allowed to complain if there's a problem?  Or, maybe not even then? SHEESH!

[A64Pilot]

His point is valid, the cell was 50 years old, well beyond I’m sure it’s expected life span. It didn’t “owe” anyone anything.

But it does bring up another point, does G100UL have a different effect on aged “rubber” components that have been soaked in leaded fuel for years? 

In truth there are just too many possible combinations to test, Africa hot, Arctic cold, Arizona dry, Florida humid? Different aged products etc, etc. Who knows how many different materials fuel cells have been made out of?

All you can do is a reasonable amount of testing, then you have to field it and sit back and wait, it could even take years before problems pop up, but of course as time goes on the probabilities decline rapidly.

Edited 14 hours ago by A64Pilot

[A64Pilot]

Apparently Mobil sold their AV-1 oil for seven years before they stopped selling it? 1987-1994?

Edited 14 hours ago by A64Pilot

[MikeOH]

1 minute ago, A64Pilot said:

Apparently Mobil sold their AV-1 oil for seven years before they stopped selling it? 1987-1994?

And, during that time, you could still buy 'conventional' oils; they were NOT banned!

[GeeBee]

46 minutes ago, MikeOH said:

So, what is 'some before G100UL'? If it was just a little while using 100LL, and then a lot AFTER G100UL, that's pretty important!

And, what's your point with "now with a new bladder we can watch?" It's been, what, a month? Or, is your expectation that we all spend the money to buy new bladders, new paint, new Viton O-rings...only, then are we allowed to complain if there's a problem?  Or, maybe not even then? SHEESH!

I said "some" because the amount of leakage is unknown, but there was evidence of recent leakage.

[A64Pilot]

52 minutes ago, MikeOH said:

And, during that time, you could still buy 'conventional' oils; they were NOT banned!

That’s California, you do have I believe a “beef” with them, but my belief doesn’t count for anything.

My point is that it took it seems years for the oil issue to play out, it didn’t happen in weeks

[MikeOH]

1 hour ago, A64Pilot said:

That’s California, you do have I believe a “beef” with them, but my belief doesn’t count for anything.

My point is that it took it seems years for the oil issue to play out, it didn’t happen in weeks

I absolutely got your point; it's the same as mine: it's going to take YEARS for the effects unleaded avgas to play out, G100UL or anything else. Precisely why I 'have a beef' with Kalifornia governmental overreach!  And those in other states should be concerned, as well.  For, if Kalifornia prevails in its ban, other states will soon follow.