Hmm. Are you claiming this based on chemistry expertise and test results, or this just what your intuition tells you? Because sometimes the real world does not behave intuitively.
Google turned up a quick citation:
“UL94 avgas has the same chemistry as 100LL — but without the use of tetraethyllead (LEAD) or its equally toxic scavenger ethylene dibromide”
Source? Swift Fuels FAQs
Thank you for the relevant comment, and especially thank you for citing your source!
But this evidence only validates “94UL IS 100LL, just without the lead added”. It does not talk about @Walkinghispath 's assertion, “then you can mix 94UL with G100UL”, which is what is relevant to the AOPA warning, “It is dangerous to create fragmented fuel availability…”. A lot hangs on whether mixing 94UL with G100UL is safe and effective.
“It’s a dangerous business, going out your door. You step onto the road, and if you don’t keep your feet, there’s no knowing where you might be swept off to.” -JRR Tolkien
You should probably just stay in your hole, where it’s safe. Best to let men with firmer constitutions do the risky things. No doubt this is your standard MO.
Another few references to peruse regarding fuel contents and intermixing are here: Swift Fuels Restricted
Interesting! Thank you for the links.
What, to your mind, do this Swift Fuels statement and Aviation Week article say about the topic of this discussion, namely the AOPA complaint about the California 100LL ban?
The problem, it seems, is that the world built by brave generalists is now run by callow specialists that cannot, or will not, think for themselves. Leaning instead on “experts” to tell them how to live.
What, to your mind, do this Swift Fuels statement and Aviation Week article say about the topic of this discussion, namely the AOPA complaint about the California 100LL ban?
The first paragraph of the complaint’s response lays it out well:
“While the availability of a 100 octane unleaded fuel at Reid Hillview Airport (RHV) and a 94 octane fuel at San Martin Airport (E16) are incremental steps forward in the unleaded fuel transition, they are not a comprehensive solution. The entire industry is working to speed a safe and coordinated transition, and we are not yet at the finish line. If the transition was easy, it would already be done. The transition to high octane unleaded fuels, in Santa Clara County and at the 3,300 other public use airports in the National Plan of Integrated Airport Systems (NPIAS), must preserve NPIAS safety and efficiency. It is dangerous to create fragmented fuel availability for the piston fleet.”
What does that mean? We are not there yet with a fleet-wide 100 octane solution.
Part of this is that many people lack understanding of the terms airplanes and aircraft in the FAA’s definition of such. Words matter. Aircraft per FAR 1.1 is “Aircraft means a device that is used or intended to be used for flight in the air.”. This covers all flying vehicles (rotorcraft, fixed wing airplanes,etc). Airplane is defined as: “Airplane means an engine-driven fixed-wing aircraft heavier than air, that is supported in flight by the dynamic reaction of the air against its wings.”
GAMI’s STC is currently only covers airplanes and engines in the FAA’s database. As noted in the complaint, it does not cover piston helicopters (i.e. an aircraft), special airworthiness airplanes (S-LSA), or EAB airplanes. So, contrary to what many believe, it is not a complete solution at this time.
To sum it up, AOPA’s complaint in this article is not anything new. It is an ongoing investigation by the FAA which has drug on (IMHO unnecessarily) for 2+ years. AOPA responded to a recent filing by the county asking for it to be dismissed (because they got G100UL at one airport). At the core of it, this is about the FAA upholding laws and regulations against a County that seeks to do what it pleases.
If one wants to get out the popcorn, the docket (dating back to Fall 2022) is here: Aircraft Owners and Pilots Association, et.al. v. County of Santa Clara, California (16-22-08)
That is a very illuminating reply, @SiliconValleyPilot . Thank you!
AOPA is correct and anyone who disagrees with them does not have the facts. With 240,000 aircraft in the US, give or take, compared to how many billions of autos in the US? Auto gas had to go unleaded, avgas does not need to be unleaded and it is a hazard to air-cooled engines to burn unleaded avgas. Exhaust valves in air cooled engines burn with unleaded mo gas after 50 to 200 hours of operation; having burned unleaded mo gas in a Cessna 172 and losing 2 separate cylinders 200 hours apart. The proof is available. No unleaded avgas, thank you very much. I was lucky having a 6 cylinder engine. It will continue to fly on 5 cylinders, not well, but will get one back to the airport. A 4 cylinder engine is very problematic; probably requiring an immediately landing where ever one is or a crash landing; after an exhaust valve failure. Until you have been exposed to the above, get real!!! Only Van Nuys, CA, has enough small aircraft traffic to warrant measuring atmospheric lead levels near or at the airport; which I believe the FAA is doing.
Terry,
Respectfully, I disagree with the substance of AOPA’s most recent filing, because, (and contrary to your assertion) it appears that “AOPA” failed to ascertain the relevant facts.
As of the time (~30 days ago) that KRHV made G100UL Avgas “commercially available”, Reid Hillview has been in full and complete compliance with its FAA Grant Assurance obligations, as defined by Congress in its most recent FAA Appropriations bill.
Because KRHV is now in full compliance with its “Grant Assurance” obligations, as most recently defined by Congress, AOPA should, in my judgment, begin to celebrate their success in advocating for their membership’s ability to fuel their high octane demand airplanes, and withdraw or dismiss their earlier complaint against KRHV.
With personal experience in a Cessna 172 using auto gas; you are wrong and AOPA is correct. Exhaust valves fail with unleaded gas; having seen it with my 172; commuting between San Diego and Reno during the last half of the 1980s. With only 240,000 aircraft in the US; no problem exists with such a small number of aircraft and flying probably 35 hours per year on average using leaded gas. It is not like auto commuters, who create a huge problem; especially in the San Francisco Bay Area; having lived there. Getting an understanding of the difference between autos and aircraft is a necessity. I am sorry; you are short on the facts. The smog in the Bay Area is from autos; fortunately no lead in auto gas; and not aircraft; having lived there. Pilots of 4 cylinder air cooled engines will likely die for no good reason using unleaded gas; losing engine cylinders from failing exhaust valves; why it is critical to keep lead in avgas. Van Nuys has at least 5 times the aircraft traffic of Reid Hillview. The only place worth measuring lead in the atmosphere from aircraft! Reid Hillview aircraft crashes will increase on unleaded gas! You can take that to the bank! And you will be one of the people responsible for these crashes; if this unleaded avgas does not go away! Cirrus will not endorse any unleaded gas for their aircraft; and for good reason!
has been in full and complete compliance with its FAA Grant Assurance obligations, as defined by Congress in its most recent FAA Appropriations bill.
Mr Braly,
Given your above statement, how do you reconcile the wording of the reauthorization bill below that says ‘aircraft’ when your fuel is only approved for a specific set of airplanes? FAA wording of aircraft includes a wider swath of flying vehicles.
Reauthorization page 271
‘‘(i) has been authorized for use by the Administrator of the Federal Aviation Administration as a replacement for 100-octane low lead aviation gasoline
for use in nearly all piston-engine aircraft and engine models; and "
Terry, I have studied this subject extensively since 1999. That includes an exhaustive literature search (SAE and FAA WJHTC research reports, among others.)
There is very good data from two reports out of the FAA WJHTC from about 1989 through 1993 that document that there are no valve wear issues with unleaded avgas - - provided the motor octane number is sufficiently high to prevent detonation of any measurable intensity.
There is race car industry experience with six cylinder air cooled race car engines that also support that conclusion.
I am unaware of any published study in which there was control over the magnitude of the internal cylinder combustion pressures - - even from the early unleaded automotive era - - that demonstrated adverse effects on valves from changing to unleaded fuels.
The valve seat problems at UND are now well understood to be related to insufficient octane for those engines to operate on UL94. Nothing to do with the lack of lead. We did a lot of that research ourselves and have reduced that to a formal written report supplementing GAMI’s earlier FAA approved detonation test reports.
Please, call me George.
Question:
A) How many airplane airframes are in service, today?
B) How many rotorcraft airframes are in service, today?
I have some understanding of how Congress intends for the phrase “nearly all” to be interpreted, based on having worked with some of the Congressional staff people and industry groups when that language was being drafted (“nearly all”) a year ago.
Regards,
George
Get out of the way of what? A bunch of people with an envirommental agenda, most of whom have no practical understanding of whether the miniscule useage of 100LL compared to other issues has any significant detrimental effect? What is your level of expertise?
Mr. Braly,
The air cooled aircraft engines from the 1940s to the 1980s, the lower
end hp engines on small aircraft were made to run on 80 octane; C-150;
C-172s, small Pipers, other small aircraft. Your assertion 94 octane is
needed is not supported by past history.
I would say that a problem exists with the UND octane tests to say
that an octane problem exists with 80 octane avgas. The small aircraft
use history from the 1940s to the 2000s refutes this supposition.
Small aircraft with 4 cylinder engines did not fall out of the
sky due to exhaust valve failure from the 1940s to the
2000s; using leaded avgas.
Your logic has holes. Sorry! Your facts are not supported
by past aircraft engine use history! And neither is UNDs!
And I will trust what I personally observed in my 172 using
unleaded auto gas over all the reports you have cited.
Unleaded auto gas will have 4 cylinder air cooled engines
losing exhaust valves, one cylinder at a time. The history of
these loses is irrefutable, if you do any amount of checking.
Nice try! Studies that do not perform real
tests over at least 400 hours of flight time
preferably 1000 hours of flight time; have
no basis. And just unleaded auto gas in
the aircraft tank is necessary for testing.
The tests need to be done with probably
over 2 dozen small aircraft in different
climates.
What ever the additions in the new supposed
unleaded avgas, need to be proven; as detailed
above. But it is a waste of time since only
240,000 small aircraft exist in the US and
maybe that many on the rest of Earth.
Spread over the entire US, leaded avgas is
not a problem compared to other air contaminants
like volcanic eruptions, have more lead from them
than all of those 240,000 aircraft in a year.
Small aircraft fly maybe 35 hours per
year on average; nothing compared to auto use.
Only Van Nuys Airport has enough small
aircraft traffic to warrant measuring lead
from aircraft engine emissions to the
atmosphere in the US; and probably
on Earth; to know what the lead level
is near and on the airport.
With something with severe outcomes
as changing small aircraft avgas; in this
case no change is warranted; probably for
another 50 years; if ever.
Battery powered aircraft will likely be taking
over the skies over the next 100 years. And
air cooled small aircraft engines using leaded
avgas will be an insignificant anomaly in the
big picture.
And for military ops; leaded avgas will always
likely be around for them. And it should be for
such a small number of private small aircraft.
Priorities matter; and yours like the rest
of the environmental community to not
consider all of the relevant facts as listed
here. Get real. All the facts matter.
Terry D. Welander
Professional Engineer
email: tdwelander@gmail.com
George,
Thank you for the response.
has been in full and complete compliance with its FAA Grant Assurance obligations, as defined by Congress in its most recent FAA Appropriations bill.
No 100 octane exists at E16.
A) How many airplane airframes are in service, today?
B) How many rotorcraft airframes are in service, today?
I have some understanding of how Congress intends for the phrase “nearly all” to be interpreted, based on having worked with some of the Congressional staff people and industry groups when that language was being drafted (“nearly all”) a year ago.
One can dice numbers in any way favorable to suit their purpose. There are ‘aircraft’ which cannot utilize G100UL. And saying only airplanes meets that standard could be a stretch. It is not a fleet-wide solution at this time. The G100UL website (F1) says:
AML STC approval for use of G100UL avgas with every spark ignition piston engine and every airframe using a spark ignition piston engine in the FAA’s Type Certificate database.
Perhaps you can add some context if I am not understanding correctly. According to the FAA database, there are some type certificated aircraft (Limited and Restricted) which are spark ignition that I cannot find in your AML. For example: Warbird (not experimental) aircraft like P-51, etc. Are these approved for use of G100UL via another method? Unless I’m missing something, I can’t see how one can claim “every airframe using a spark ignition piston engine in the FAA’s Type Certificate database” is true if they have Type Certificates, unless it is narrowed to a category.
IMHO, a County that uses back channels in order legislate a way out of ~3 years of grant non-compliance by ‘favorable’ language is a pretty shady way of absolving oneself of FAA agreements and causing harm to many airport users.
Masters MIT engineer.
Lead is bad for you. And your plane. Full stop.
Every single spark ignition piston powered airplane that is found in the FAA database of Part 23 and CAR 3 certified airplanes is approved to use G100UL Avgas, directly, via the STC process.
That is around 220,000 airplanes.
The very small number of “other” airplanes that are “out there” that use certified spark ignition engines, can also be approved to use G100UL avgas via an alternative method, among others, by a field approval, relying on the FAA approved data that supports the G100UL STCs.
Each of the CAF warbirds is also eligible by the same process. We have already demonstrated that by successfully obtaining the approval for a P-40 Warhawk and for the Douglas A-26.
There are about 3,444 rotorcraft in the data bases. About 1.5% of the total number of aircraft.
Having the approval for 98.5% of the aircraft - - appears to be a circumstance that demonstrates compliance with the 2024 Congressional reauthorization act that allows 100LL to be discontinued in the event the FAA has approved the use of a high octane avgas for “nearly all” of the aircraft.
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