G100UL - fuel leak

[A64Pilot]

4 minutes ago, gabez said:

is the diaphragm in the flow divider be affected by the G100? 

Who knows? I had assumed not because surely that was tested, but I thought the same for O-rings too.

Anything in my opinion that swells fuel resistant O-rings literally almost overnight is questionable to be put kindly.

I don’t what the diaphragms are made of I had assumed Nitrile as it’s sort of been the go to for a long time, but assumptions are just guesses under another name.

[A64Pilot]

My guess is that there are a few in the FAA that are saying Uh-Oh, can this get me in trouble?

[Marc_B]

21 minutes ago, A64Pilot said:

My guess is that there are a few in the FAA that are saying Uh-Oh, can this get me in trouble?

Sounds like the birth of an AD.

[GeeBee]

1 hour ago, Will.iam said:

Well they could use the people like me that are in the aviation field professionally and i used to use 100LL to wash parts with “gasp” no gloves on as a kid and young adult before this became a nono. Went to a holistic doctor that just knew i had lead in my body but when the lab results came back he was shocked i did not. Either the issue is overblown or my body seems to be able to remove what lead i do get into my system. My A&P routinely washes his hands with 100LL to this day. He is 78 been doing it all his life. He said if it has not killed him yet it’s not going to now. 

Yeah, it's being held captive in you liver and brain cells.

[PT20J]

1 hour ago, gabez said:

is the diaphragm in the flow divider be affected by the G100? 

Bendix changed all the diapgragms in the servo and flow dividers to flourosilicone in 1980.

https://precisionairmotive.com/wp-content/uploads/2019/06/RS-76-Rev1.pdf

[IvanP]

13 minutes ago, PT20J said:

Bendix changed all the diapgragms in the servo and flow dividers to flourosilicone in 1980.

https://precisionairmotive.com/wp-content/uploads/2019/06/RS-76-Rev1.pdf

Do we know how does fluorosilicone behave when exposed to G100UL?

Edited 17 hours ago by IvanP

[PT20J]

According to Parker, some o-ring swelling is acceptable when the o-rings are exposed to fluids. The bigger problem is if the exposure causes shrinkage.

ORD-5700.pdf

[Pinecone]

2 hours ago, Will.iam said:

Well they could use the people like me that are in the aviation field professionally and i used to use 100LL to wash parts with “gasp” no gloves on as a kid and young adult before this became a nono. Went to a holistic doctor that just knew i had lead in my body but when the lab results came back he was shocked i did not. Either the issue is overblown or my body seems to be able to remove what lead i do get into my system. My A&P routinely washes his hands with 100LL to this day. He is 78 been doing it all his life. He said if it has not killed him yet it’s not going to now. 

The problem is not finding people who have been exposed to lead.  But to find those with NO exposure to show that the lead is the cause.

Just because everyone who is exposed to lead has X issue, doesn't mean the lead caused it.  You need to show that those not exposed don't have X issue.

[Pinecone]

8 minutes ago, PT20J said:

According to Parker, some o-ring swelling is acceptable when the o-rings are exposed to fluids. The bigger problem is if the exposure causes shrinkage.

ORD-5700.pdf 28.68 MB · 1 download

That is what GAMI is saying.  

[Marc_B]

The main issue I have with this, is that there have been instances of damage to aircraft and potential damage to elastomers used in the aircraft.  You'd think for an STC that the manufacturer would be responsible for proving that if modifications were or were not needed and be able to show open and clear data as such regarding what was tested and what wasn't.

GAMI (or any potential fuel manufacturer) is the one that should be responsible for convincing me as the owner and operator that their product is safe.

Continental and Lycoming have a list of authorized fuels by engine model (doesn't include high octane UL).  I'm not sure which o-rings, hoses, and seals could potentially be at risk.  It's not OUR job to be test pilots with our aircraft, paint, tank seals, and potentially our own lives and the public, solely because we care to remove lead from the environment.  FACT: GA pollution is not only just lead.

Just saying that "we know about that and we're okay with it" or "don't worry about your paint because that's cosmetic and doesn't matter to us" or "you have wet wings and they leak from time to time so it's not our fault if that's accelerated"...doesn't address the concern.

FROM GAMI's G100UL ICA:

"When replacing seals or O-rings in the fuel systems of aircraft or engines operating on G100UL Avgas replace Buna N or nitrile fuel system components with components made of silicone or fluoropolymer elastomers (such as Viton) where practical. When replacing flexible fuel hose assemblies utilize tetrafluoroethylene (Teflon) lined hose assemblies per TSO C53a or TSO C140 where practical."

If my Airframe and my Engine is on your STC AML...you should be able to tell me exactly which parts that I need to replace to run your fuel safely.  It is your job to prove safety, not mine.  You are the STC holder that has shown your data to the FAA, and you haven't shown this to me.  So if your product is ultimately unsafe or leads to unairworthy condition, the liability is yours.

I cringe when I hear "we have to stop loving the problem" because the follow up is we need to start loving a new problem.

 

[EricJ]

8 minutes ago, PT20J said:

According to Parker, some o-ring swelling is acceptable when the o-rings are exposed to fluids. The bigger problem is if the exposure causes shrinkage.

ORD-5700.pdf 28.68 MB · 0 downloads

That's a bit of an oversimplification, I think.    Some swelling is expected, and beneficial, but excessive swelling (as seen in the vid) is detrimental, as described in the linked document.    For an o-ring used as a static gasket, 20-30% swell is acceptable, but for a seal (dynamic), only 10% or so is allowed.   Swelling also weakens the material and makes it more susceptible to tearing (for a seal) or extruding out of the groove for a gasket.    The issue as noted in the vid is that the swelling was significantly past acceptable limits, especially for a dynamic seal.

Mooney fuel systems have dynamic o-ring seals in the fuel selectors, gascolators, carburetors, fuel servos, etc.   An excessively swollen o-ring in any of those may restrict or seize the motion of the sealed shaft, or may tear when the sealed surface moves, resulting in leaks.   None of that is good, and excusing excessive swelling as just "it'll seal better" is ignorant at best and disingenuous at worst imho.

[PT20J]

21 minutes ago, EricJ said:

That's a bit of an oversimplification, I think.    Some swelling is expected, and beneficial, but excessive swelling (as seen in the vid) is detrimental, as described in the linked document.    For an o-ring used as a static gasket, 20-30% swell is acceptable, but for a seal (dynamic), only 10% or so is allowed.   Swelling also weakens the material and makes it more susceptible to tearing (for a seal) or extruding out of the groove for a gasket.    The issue as noted in the vid is that the swelling was significantly past acceptable limits, especially for a dynamic seal.

Mooney fuel systems have dynamic o-ring seals in the fuel selectors, gascolators, carburetors, fuel servos, etc.   An excessively swollen o-ring in any of those may restrict or seize the motion of the sealed shaft, or may tear when the sealed surface moves, resulting in leaks.   None of that is good, and excusing excessive swelling as just "it'll seal better" is ignorant at best and disingenuous at worst imho.

Well, you are probably the only one that read the document and everything you say is contained therein. My point is that GAMI did fuel system materials compatibility testing and the FAA evidently approved it. So, the swelling is likely in the expected and acceptable range and may be slightly beneficial which is what George has said. My point is that just because there is some swelling does not necessarily mean that there is a problem in service. George made the comment the Viton is a better material which is also true, but some have extrapolated this to mean that G100UL will require replacing all the o-rings in the fuel system which no one (GAMI or FAA) has said. I'm not defending GAMI or the FAA, but I think we need to understand the facts. I would like to see testing done to industry standard specifications and the results published. Keeping the nature and extent of testing under wraps creates suspicion (maybe well founded if the results are suspect).

Frankly, I'm more worried about the paint. George said somewhere in one of these threads that he soaked (ten I think) panels from customer's Bonanzas for a week or so with no ill effects. That doesn't sound like a very scientific or controlled test. And, perhaps Beech used better primer or did a better paint job than Mooney.

The original 1994 paint on my M20J is flaking off on the leading edges and a lot of flat rivet heads that are not loose. I talked to Brandon and Sunquest where I am planning to paint my plane this spring and he said he has seen a lot of that on Mooneys. My 1978 J was only 15 years old when I sold it and the original paint was very thin and starting to wear through. So, I think the testing should have involved a lot of different components from different airplanes and different vintages in varying condition.

[Marc_B]

Continental's response to what fuels are safe for my engine:

Does anyone know what the testing process was to approve the IO-360-AF with the FAA?  i.e. what materials and elastomer testing was required by the FAA?  Perhaps there already IS a benchmark for testing to approve equipment for alternative fuel use?

Also, what was the testing process for Peterson with STC approval with the FAA?  Was this at all similar to the process that GAMI has gone though or much different??

[Will.iam]

4 hours ago, GeeBee said:

Yeah, it's being held captive in you liver and brain cells.

Fake news. 

[toto]

4 hours ago, PT20J said:

Frankly, I'm more worried about the paint. George said somewhere in one of these threads that he soaked (ten I think) panels from customer's Bonanzas for a week or so with no ill effects. That doesn't sound like a very scientific or controlled test. And, perhaps Beech used better primer or did a better paint job than Mooney.

The video definitely made it seem like the issue was differences in evaporation behavior between 100LL and G100UL, where some component of the G100UL evaporated very slowly and pooled at the edges of the paint. It may be that fully submerging a painted inspection panel and then cleaning and drying it on removal will result in no visible damage, but allowing it to dry on its own causes the peeling and flaking. 

[A64Pilot]

8 hours ago, Marc_B said:

Sounds like the birth of an AD.

I wouldn’t say anything like that, just from my experience with working with them, the primary motivating factor was the question “could this reflect bad on me”

If the answer was no, then you got approval, if the answer was possibly then they passed the buck, and if yes, then the answer was no.

[A64Pilot]

1 hour ago, toto said:

The video definitely made it seem like the issue was differences in evaporation behavior between 100LL and G100UL, where some component of the G100UL evaporated very slowly and pooled at the edges of the paint. It may be that fully submerging a painted inspection panel and then cleaning and drying it on removal will result in no visible damage, but allowing it to dry on its own causes the peeling and flaking. 

Very many mixtures behave like that, for instance many if the new refrigerants are mixtures of different gasses, some have smaller molecules and are very prone to leak out while others don’t, so over time you end up with a mixture of gasses very unlike what you started with.

[A64Pilot]

From a paint perspective, when we restarted production of the Thrush, we had many paint issues. I found that the paint we were using was cheap junk, so I started looking for a good paint in the belief that frankly you get what you pay for.

In my research I found out that at least back then that Air Force One, The Thunderbirds and Blue Angels all were painted with the same paint, Sherwin Williams Jet-Glo. Under the belief that it’s likely that those aircraft most likely used the best paint available I went with Jet-Glo, and almost overnight our paint problems went away, and yes it was expensive, but our rework went down so much it more than made up the difference.

I believe the C-182 panels tested in that Video were painted with Jet-Glo and Jet-Glo was the paint that held up best to agricultural chemicals that we found, it’s good stuff.

I don’t think paint is a safety issue, but I do think it may be the Canary in the coal mine, anything that dissolves Jet-Glo is something that’s pretty aggressive I think.

If it were a failure of the primer the paint would peel off but the paint look otherwise unaffected, but that video showed it wrinkled, which to means it’s being dissolved

Edited 9 hours ago by A64Pilot

[MikeOH]

9 hours ago, GeeBee said:

Yeah, it's being held captive in you liver and brain cells.

Depends on your definition of captive.

Lead has around a 1 month half-life in blood, 2 months in soft tissue, 2-3 years in the brain, and 20-30 years in bone.

Other interesting info:
1) OSHA PEL 8-hour shift atmospheric workplace limits are <50 ug/cubic meter.
2) SoCal AQMD ran a study at Whiteman airport (KWHP) with the following results (note these data are in nano-grams/m^3, 1000 less than micro-grams/m^3!):

 

 

[MikeOH]

8 hours ago, PT20J said:

According to Parker, some o-ring swelling is acceptable when the o-rings are exposed to fluids. The bigger problem is if the exposure causes shrinkage.

ORD-5700.pdf 28.68 MB · 10 downloads

Can you please point to where that is discussed in that document?  And, do they define 'some' swelling?  IIRC, the video from the A&P showed the swelling exceeded the parts' tolerance by a significant amount; like 10%.  Is that acceptable as 'some swelling'?

Maybe it's just me, but having a part dimensionally change by over its design limits is NOT acceptable.  Look at this way, if you bought a new O-ring and it was 10% out of tolerance would you go ahead and install it, or return it?  You'd be correct if you guess I'd return it!

[PT20J]

1 hour ago, MikeOH said:

Can you please point to where that is discussed in that document?  And, do they define 'some' swelling?  IIRC, the video from the A&P showed the swelling exceeded the parts' tolerance by a significant amount; like 10%.  Is that acceptable as 'some swelling'?

Maybe it's just me, but having a part dimensionally change by over its design limits is NOT acceptable.  Look at this way, if you bought a new O-ring and it was 10% out of tolerance would you go ahead and install it, or return it?  You'd be correct if you guess I'd return it!

[PT20J]

Most of the o-rings in the fuel system are static (for instance the o-rings in the fuel pump fittings and the servo finger screen). The o-rings in the gascolator and fuel valve are dynamic. In my M20J, these components use MS9388 o-rings which are Fluorocarbon (Viton/FKM) which is rated by Parker as satisfactory (highest rating) for fuel containing 50% aromatics according to Section VII of the Parker O-ring Handbook.

[PT20J]

I looked at the video posted by the A&P at KRHV again. The o-rings he tested were MS28775 and MS29513 which are both nitrile which is listed in Section VII or the Parker O-ring Handbook as having only fair compatibility with 50% aromatic fuels.

Also, the test may not be representative of the fuel's effect on the o-rings in service. Specifically on Page 2-7 of the Handbook, it is stated: "When deformed and exposed to a medium, rubber (Note: Parker uses the descriptor "rubber" to refer generically to any o-ring material), when confined in a gland, swells significantly less that in a free state (up to 50%) due to a number of factors including lessened surface area in contact with the medium." 

I just checked and SAF-AIR fuel drain valves use M83248 o-rings (Viton).