Originally published at: House Bill Targets Unleaded Avgas Education
Proposed legislation would require FAA to provide guidance on fuel approvals, compatibility and availability.
Instead of wasting time and effort with this, maybe congress should mandate a grade of unleaded auto fuel without ethanol. That way it could be used for some aviation uses. This latest E15 allowance/mandate will end up ruining older vehicles and lawn equipment besides being completely unusable for aircraft.
You notice that everything involving future unleaded aviation fuel involves a target date, no mandates. Target dates have come and gone in the past involving drop in replacement for 100LL and nothing happens, except they come up with a new target date.
The current replacement unleaded fuels in contention will not be happening. One replacement has no ASTM approval and will require an STC to use it in your plane. The other two will also need STC’s to be used, but get this, they both contain an ETBE additive that is environmentally damaging, and gets into ground water, which has already been a big problem from its past use in auto gas as an oxygenator.
It is pretty obvious, that none of these three will be used as a drop-in replacement. The FAA and AOPA will keep pushing this unachievable goal, and keep telling us it will happen, adding you must trust us. Do not trust them on this matter as they have proven, they will not be able to achieve this impossible goal.
Currently the best efforts to achieve a goal of unleaded aviation fuel has come about in Europe, where they are currently using an ASTM approved UL91 product which is normally sold with the current 100LL fuel. The UL91 can be used by 70% of aircraft without any STC because these aircraft were already approved to use it.
If we want to see any progress in eliminating Lead Fuel in the USA we need to follow this example. This will also lead to much lower cost for maintenance and the fuel itself for aircraft that can currently use it.
As a scientist who’s worked in formulation, I can promise you that finding a drop-in replacement for 100LL (or any other complex mixture) that is exactly the same is unlikely to happen. Science (the real world if you wish) simply does not work that way. There will always be some differences, some compromise you have to accept and it often involves cost. Aviators need to understand this compromise. An exact replacement that you cannot afford to buy probably exists. Nobody wants that. I would prefer to have a functional replacement that works in the entire fleet without compromise with respect to engine performance and longevity. Plus, unleaded fuels will permit the use of synthetic oils. That is the big payoff. Imagine all the cams we’ll save.
A couple other minor details. Two of the alternative fuels use ETBE, not MTBE. Not quite as water soluble but still a potential environmental issue. Their big problem is they carry oxygen and will lean your engine whether or not you want to lean it. The more you add, the worse it gets. Detonation becomes a problem and you have to retard your timing advance. This will kill performance in high performance/turbo engines. ASTM is a standards organization that writes documents that tell you how to test things. They do not approve any material. They only write the test standard. Your testing either complies with the standard or it doesn’t. GAMI has not written an ASTM test standard for their fuel. They went the STC route. This is arguably more complicated bureaucratically but less so politically. Their fuel isn’t an exact match to 100LL but wouldn’t require an owner to de-tune their engine to keep all the pistons in one piece. And you can afford to buy it. Personally, I’ll take that compromise. You should visit their website and read how they test. It’s pretty impressive.
The problem I have seen I. This mess is that the current ASTM spec has requirements that have zero and i mean zero influence on performance . This is something we worked hard at eliminating in aerospace I’ve my career. By focusing on performance metrics the supplier provides what does the job. Now material compatibility is a performance metric and many standard tests can adress that. Right now ( working on memory) gamis fuel meets everything but density. Is the spec requirement as stars a performance requirement? No I is an information requirement and opening it up to a more reasonable value vs coming it from the leaded spec is easy and in no consequence as the deviation is small .
Next the ASTM has never approved any material I had qualified to there spec every why in the world does the FAA or ASTM think they have any say NOW. All material I purchase approved specified were deemed to meet our spec which call out ASTM specs by the supplier. If there is an issue later we will audit them
But not until.
Note aircraft do not fall out of the sky because aluminum did not meet spec!
Problem is the air cooled Lyconasauros engines with hot spots. Modern liquid cooled engines such as Rotax or MWFly will run on unleaded auto gas with or without ethanol. Rotax prefers unleaded without ethanol but it is better to run unleaded with ethanol than to run 100LL which is not Low Lead. I fly with a new Rotax with electronic fuel injection which I do not want to wreck with100LL.
Solution which has been around since at least 1940 for those that can run a new engine is to run non-ethanol unleaded and use ethanol or ethanol water injection. This is already used in aircraft race engines.
Of course, the real solution is to get rid of internal combustion engines and go electric. Low cost fuel, little or no maintenance, much quieter and less pollution. Batteries are getting better.
Ehsif72, you hit the nail on the head!
Because of the (unobtainable) quest for the mythical “single fuel drop-in” replacement for 100LL, we have completely ignored the 70% solution for decades. 70% of the GA fleet could have been “unleaded” for the last 30+ years.
The added benefit of a reliable sourced fuel like UL91 is that higher performance engines will be developed to use it (e.g.: Rotax) which will evolve general aviation powerplants instead of keeping dinosaurs on life support.
Implementing the 70% solution will get an immediate and meaningful reduction in GA lead emissions and buy GA the time to develop more sophisticated powerplants. If this process was started in 1991 (when UL91 was introduced in Europe), all new GA aircraft today would be flying behind full FADEC EFI engines.
No matter whether the 70% of GA planes could use unleaded now or not or whether a drop-in unleaded 100octane is possible, FBO’s are not able to justify the cost of multiple grades of avgas. EPA rules and volume is too low, otherwise the old 80 octane that used to be sold would still be for sale. I am able to obtain ethanol free 90 octane auto fuel to run in my C172 with a O300 engine. The government needs to make some premium auto fuel available without ethanol. Problem is there are liability issues with running auto fuel in planes the oil companies don’t want to deal with, and then there is the farm lobby that wants more ethanol in gasoline.
The Hjelmco AVGAS 91/96 UL was introduced in Sweden year 1991 and is still the
dominant AVGAS in Sweden. It was approved by Lycoming year 1995. UL91 is not the Hjelmco fuel.
The Hjelmco fuel is octanwise more like UL94 -but not with any of the problems associated with UL94 in the US.
The story about FBO:s cannot handle two AVGAS types is just not correct. Sweden has for all the time maintained both the unleaded AVGAS and the leaded 100 LL when so is requested. And the volumes in Sweden are so much lower than in the US.
Then I question the idea that AVGAS is the major lead polluter in the US. Unleaded car gasone is not free of lead. Crude oil contains metals so the maximum lead content
allowed in unleaded car gasoline is 0.013 gram/liter fuel. As AVGAS in the US is less than 1 % of car gasoline you should take into consideration the lead from road fuels when you make a prediction.
The Hjelmco AVGAS 91/96 UL is a real 100 % drop in fuel if your engine has hardend valve seats which were introduced around 1978 in the US when aromatics were introduced in AVGAS. (The reason - aromatic combustion deposits can be so hard that the valve seat can be damaged) Also this fact was found out in Sweden in the 1970:ies when AVGAS 100 L (green) was introduced to replace grade 100/130. Unleaded grade AVGAS 80 UL was introduced in Sweden on a nationwide basis already year 1981.
The important thing when introducing a new aviation fuel is primary to satisfy the engine and its combustion. A second and later issues would be to try to satisfy the octane numbers. Now the US in their efforts to find a 100 LL replacement has chosen the way to first trying to satisfy the octane numbers and then satisfy the engine. That will not prove well for the future. All 100 UL fuels in the US currently are outside the parameters for satisfying the engine first - the parameters which the US Air-force after trial and error had found to be the best ones and after 100 of thousands of flight hours.
GAMI detailed changes they want to the ASTM standard and things that should be added. All detailed on GAMI’s web site.
Their mouthy competitor has made some progress in meeting the standard.
I am pedantic, a ‘standard’ is for performance, a specification is details of a particular approach to meeting it.
For metals in aircraft, strength, ductility, corrosion resistance are common factors.
(Can be application dependent, so lower wing skin is often 2024 series alloy while upper skin is often 7075 series.
Corrosion has variables - upper wing skin of L188 Electra Airliner was prone to intergranular corrosion in its milled construction: I’ve seen the ‘rib’ portion separate from the ‘skin’ portion. (Rolling sheet aluminum tends to elongate granules in the material
(unsure of the term granules).)