Based on the G100UL fuel leak thread what's your position?

[redbaron1982]

https://youtu.be/PYaSfBu2WXI?t=1304

[IvanP]

7 hours ago, MikeOH said:

In a word, "yes", people are going to die before the FAA rescinds their blanket STC.  As you point out, that's what it has taken in the past; this situation is no different.  Maybe even worse since the politics of "lead is EVIL" is likely more problematic than biz jets for the rich.

Maybe the powers to be are taking the position that few folks crashing their little annoying airplanes does not matter because we are saving the entire planet from slow and painful death caused by lead emissions from 100LL.

Sarcasm off...

On a more serious note, what would be the result of o-ring failure in the Cessna fuel selector that Mike had shown in his video? I am not familiar with that design. would it cause massive leak and possibly fuel starvation or fire? 

[EricJ]

1 hour ago, IvanP said:

On a more serious note, what would be the result of o-ring failure in the Cessna fuel selector that Mike had shown in his video? I am not familiar with that design. would it cause massive leak and possibly fuel starvation or fire? 

There are a number of failure modes evident in the video.   As originally reported, the control handle can be jammed by the o-ring fragments which could prevent selection of a tank or crossfeed, and also prevent being able to shut the fuel off to an engine fire.   The o-ring fragments were shown to be able to flow out from the selector to the engine, which can certainly cause issues.   Also, since the o-ring disintegration or displacement from their grooves essentially removes them from the system, there could be some uncontrolled flow between all of the ports on the selector, in other words, you lose complete control over the fuel flow.    It should not cause an external leak unless the main o-ring to the control shaft failed, which didn't fail in the examples, presumably because it is always in a constrained configuration, unlike the smaller o-rings in the system.

It's a dangerous situation, IMHO.  It's also not an isolated case, as nitrile/buna-N/etc. rings are still widely used in general aviation.

[hazek]

At this time stamp (28:54) truth of the matter is stated. No fuel is perfect, we can all agree certainly not 100LL. But he seems to admit here also not G100UL. They got it to work for the engine so they think for the rest of the problems caused by its bad side need to be fixed by finding solutions on the other side of the equation. In other words, G100UL is fine for for your engine, maybe even better, as for the interactions with other materials we don't care, just find better ones, you're on your own. And if you can't or if that costs you a lot of money, well.. that's just your bad luck.

I guess it's an approach.

 

[IvanP]

3 hours ago, hazek said:

At this time stamp (28:54) truth of the matter is stated. No fuel is perfect, we can all agree certainly not 100LL. But he seems to admit here also not G100UL. They got it to work for the engine so they think for the rest of the problems caused by it's bad side need to be fixed by finding solutions on the other side of the equation. In other words, G100UL is fine for for your engine, maybe even better, as for the interactions with other materials we don't care, just find better ones, you're on your own. And if you can't or if that costs you a lot of money, well.. that's just your bad luck.

I guess it's an approach.

 

Yes, more of the same stuff that we have seen. Kind of like some computer software companies approach - "this is not a problem, it is a feature of the program". George was trying really hard to convince everyone that swelling of o-rings is actually good for the fuel systems. Then why would the various manufacturers go to such great lengths to actually specify permitted variations of o-rings? 

My hope is that we will be given a choice of what UL fuel to purchase for our planes, rather than being forced to buy stuff that causes damage. For so long as other options are available I am not putting this stuff in my plane. 

[A64Pilot]

That varnish build up the dip stick on that Bonanza makes me think it may not be fine for your engine, but that possibly  will take hundreds or thousands of hours to manifest.

If there was going to be a problem with the G100 fuel I didn’t expect them to surface for a long time as none of the testing I’m aware of went for years and to TBO, I was very surprised several surfaced right out of the gate. I’m thinking the formulation of what’s being sold is different than what was tested, I theorize that the formulation is sort of loose meaning pretty wide tolerances in percentages of each component or possibly allows different formulations with I assume Octane being the driver. But that’s unfounded speculation.

I don’t see how you can fix the problems myself, what kind of fuel cells will survive it, or are we supposed to accept say a five year or less life of cells and tank sealant, paint etc. I think it’s going to start eating boost pump seals and every non metal part it come into contact with.

[gabez]

5 hours ago, A64Pilot said:

That varnish build up the dip stick on that Bonanza makes me think it may not be fine for your engine, but that possibly  will take hundreds or thousands of hours to manifest.

If there was going to be a problem with the G100 fuel I didn’t expect them to surface for a long time as none of the testing I’m aware of went for years and to TBO, I was very surprised several surfaced right out of the gate. I’m thinking the formulation of what’s being sold is different than what was tested, I theorize that the formulation is sort of loose meaning pretty wide tolerances in percentages of each component or possibly allows different formulations with I assume Octane being the driver. But that’s unfounded speculation.

I don’t see how you can fix the problems myself, what kind of fuel cells will survive it, or are we supposed to accept say a five year or less life of cells and tank sealant, paint etc. I think it’s going to start eating boost pump seals and every non metal part it come into contact with.

I have never in 10 years of flying and 2 aircrafts one was a 1958 J35 had worried about 100LL staining or chewing through parts. When I got my J35 it had a huge blue stain cos the bladder was leaking, we replaced the bladder and wiped off the stain. 1-2 weeks with G100 and both thanks are leaking and the paint is stripped to the metal....and I am not the only one. 

Edited April 29 by gabez

[redbaron1982]

I think this is good news:

https://www.avweb.com/aviation-news/faa-updates-airport-grant-assurance-requirements/

[Fly Boomer]

13 minutes ago, redbaron1982 said:

I think this is good news:

https://www.avweb.com/aviation-news/faa-updates-airport-grant-assurance-requirements/

Sounds promising but I hate to see weasel words like “becomes widely available”.

[MikeOH]

48 minutes ago, redbaron1982 said:

I think this is good news:

https://www.avweb.com/aviation-news/faa-updates-airport-grant-assurance-requirements/

I hope the $2.49 price is part of the grant assurance requirements 

[redbaron1982]

10 minutes ago, MikeOH said:

I hope the $2.49 price is part of the grant assurance requirements 

I was thinking the same when I saw that picture 

[gabez]

new disclaimer added when you buy the STC. even if nothing is wrong with your aircraft and 100LL you still need to replace components.....still drop in LOL 

Edited May 30 by gabez

[Pinecone]

Nothing required.

The recommendation to change to fluorosilicone or Vitron components has been there since before the STC went live.

The FAA wanted this as they have been trying to get the old materials changed out for over 20 years.

[Paul Thomas]

G1000UL is still trying to open new markets; last I read was in TN.

George Braly seems to still be reading MooneySpace even though it doesn't appear to be participating. He used a photo posted here, in the last week or so, of a C model with leaking tanks to show that Mooney tanks leak.

Edited May 30 by Paul Thomas

[PT20J]

50 minutes ago, Pinecone said:

The FAA wanted this as they have been trying to get the old materials changed out for over 20 years.

Is there an advisory circular or some other documentation on this? I’m asking because the only source I have seen for this is a statement by George Braly. It may be true, and I may have missed some notice from the FAA.

[N201MKTurbo]

Where is the approval to change the o-rings? I know everybody does it, and nobody really cares, but from a regulatory standpoint, what gives us the authority to do it?

[N201MKTurbo]

On 4/29/2025 at 3:37 PM, MikeOH said:

I hope the $2.49 price is part of the grant assurance requirements 

Ah, the good old days. I remember paying $1.24/gal at the Meadowlike airport south of Denver back in '84 Just after I bought my first Mooney.

[IvanP]

18 hours ago, gabez said:

new disclaimer added when you buy the STC. even if nothing is wrong with your aircraft and 100LL you still need to replace components.....still drop in LOL 

I like the part that says: "These issues should be evaluated prior to the use of this paroduct." 

Well, I evaluated them and decided not to use a product that appears to have some substantial design defects. Of course, the choice may be taken away pretty soon by the government zealots. 

Not interested in taking apart the entire fuel system to find out what o-rings and hoses are installed and replacing them with product that can tolerate G-brew. 

[redbaron1982]

19 hours ago, gabez said:

new disclaimer added when you buy the STC. even if nothing is wrong with your aircraft and 100LL you still need to replace components.....still drop in LOL 

Meanwhile, Scott Perdue continues lobbying for GAMI. He published a video saying that mluvara oring test is incorrect. In the same video Braly demonstrated that hot 100LL with toluene added on top destroys orings, which is evidence that 100LL (and not the hot temperatures or added toluene) is the problem. 
 

 

[IvanP]

So they tested the wrong part and it failed. What is the probative value of such test? Am I missing something here? 

[hazek]

12 hours ago, redbaron1982 said:

In the same video Braly demonstrated that hot 100LL with toluene added on top destroys orings, which is evidence that 100LL (and not the hot temperatures or added toluene) is the problem.

They're pissing on us and trying to convince us it's rain. Plain and simple.

[Sabremech]

14 hours ago, redbaron1982 said:

Meanwhile, Scott Perdue continues lobbying for GAMI. He published a video saying that mluvara oring test is incorrect. In the same video Braly demonstrated that hot 100LL with toluene added on top destroys orings, which is evidence that 100LL (and not the hot temperatures or added toluene) is the problem. 
 

 

This video is so poorly done. I don’t think this is going to help their cause. 
David

[gabez]

CEH lost completely. The final order is available online. 

[IvanP]

1 hour ago, gabez said:

CEH lost completely. The final order is available online. 

Can you please post the link? 

[Marc_B]

5 hours ago, Sabremech said:

This video is so poorly done. I don’t think this is going to help their cause.

I'm scratching my head with most of the posts that come out of Ada.

Does anyone know the background with the Cessna 421 fuel selector?  I gather that likely -14 o-rings used originally?/commonly?, but at least one shop says it's better to use -13 to have less issues?  Of course Mr. Braly "cooks" the results.  It sounded like he used increasing amounts of added toluene until he could reliably reproduce failure...yet even with this, G100UL has higher aromatic concentration than his "100LL + 20% toluene".  Interesting that he commented that with -14 viton o-rings that he didn't see failure.  I take this to imply that -14 o-rings actually work in the application, but the failure is seen with induced elastomer swell.  Certainly it's no surprise that G100UL would fail with this, as xylene contributes to o-ring swell more than toluene.

I've never gotten an answer to the question of aromatic content of G100UL...although I know that Mr. Braly knows each of the DHA in order to "stamp" as conforming.  SDS shows xylene 40% and toluene 5%.  It was clear in Mr. Luvara's videos that even "uncooked" o-rings markedly swell with G100UL.  Certainly fits with the higher aromatic content of the fuel and the use of xylene rather than toluene.

It's been a strange story of G100UL, CEH lawsuits, strange/misguided "advertising", and a weird blame on "high aromatic 100LL".  Truth is truly stranger than fiction.