The FAA released its final Transition Plan to Unleaded Aviation Gasoline on Thursday, outlining a four-phase process intended to move the U.S. piston fleet away from 100LL.
The 72-page document responds to an unleaded avgas requirement in the 2024 FAA Reauthorization Act and retains the goal of eliminating leaded avgas use by the end of 2030 outside Alaska. The state would receive an additional two years due to its unique set of fuel-distribution and operational challenges.
This final plan comes months after the FAA released a draft version of the plan in January. Despite an active comment period on the draft version, formal comments on that version of the plan have yet to be released to the public.
The FAA did say in the final plan that the 60-day comment period prompted revisions addressing Phase 1 progress, possible aircraft modifications, fuel mixing, regulatory timing and cost. The agency also committed to regular updates during Phase 1, a revised transition plan in late 2027, a public FAQ and a separate document summarizing substantive comments and explaining how the FAA handled them.
Unleaded Avgas Testing Comes Before Full Transition
Phase 1 of the final plan covers fuel approvals and direct comparisons among the three high-octane candidates: GAMI G100UL, Swift Fuels 100R and LyondellBasell/VP Racing UL100.
The FAA projects that work will be completed in spring 2027. Phase 2 would expand market use and gather operational experience, and is projected to conclude by mid-to-late 2028.
“The transition to unleaded fuel is a positive step forward for general aviation community and people who live and work near general aviation airports,” FAA Administrator Bryan Bedford said in the agency’s announcement. “Our move to safely integrate unleaded fuels is a collaborative effort that involves everyone from aircraft manufacturers and fuel suppliers to airports and the pilots in the cockpit.”
The FAA has not established firm start dates or detailed schedules for Phase 3, the national transition outside Alaska, or Phase 4, the Alaska transition. Phase 3 is intended, however, to complete the changeover outside Alaska by the end of 2030, while Phase 4 carries an end-of-2032 goal.
The agency expects to define those schedules, milestones and regulatory actions for both phases in an updated plan after Phase 1 is completed, tentatively in late 2027.
The FAA plans to compare the three candidate fuels under common test conditions. The program will examine detonation performance, engine operation, material compatibility, fuel composition and other properties. Testing will also address the effect of mixing each unleaded avgas with 100LL and combining different unleaded fuels.
Each developer supports mixing its product with 100LL inside an aircraft tank, according to the plan. None currently supports mixing its unleaded fuel with a competing unleaded avgas.
Aircraft Will Require Individual Action
The plan makes clear that FAA approval of a fuel does not automatically authorize every individual aircraft to use it without further action. At a minimum, each aircraft will need a new fuel placard, revised operating information and a logbook entry. A certificated mechanic or repair station generally must complete those changes for aircraft holding standard airworthiness certificates. Some airplanes may require additional work involving ignition timing, fuel-system materials, pistons or other engine hardware.
The authorization route will depend on the fuel. G100UL and 100R have received supplemental type certificate approvals of differing scope, while UL100 is pursuing fleet authorization through the FAA’s Piston Aviation Fuels Initiative. Swift has also entered PAFI to seek fleet authorization for 100R.
The FAA expects the marketplace to determine which fuel or fuels replace 100LL, although the plan acknowledges that incompatible products could divide the country into regional fuel markets and increase the risk of misfueling.
“The transition plan assumes right now that the market is going to decide, and that’s probably not realistic,” AOPA acting Co-President Katie Pribyl said during an AirVenture forum, according to AOPA. “We want the FAA to have a role in that beyond just approving fuels. They’re doing the testing. We believe that they’re in the best position to help the industry come to that decision on what that fuel is going to be.”
Phase 2 would give aircraft owners, flight schools, airports and fuel suppliers time to gain operating and distribution experience before the national changeover. The plan calls for 100LL to remain available during that period. Federally obligated airports that offered the fuel in 2022 generally must continue doing so until statutory replacement criteria are satisfied or the applicable transition deadline is reached.
Airports that cannot store two grades of avgas may need temporary unleaded avgas tanks, fuel trucks or other equipment before becoming early adopters. The FAA says airports and FBOs should not be required to install additional permanent tanks solely to support the transition. At locations that can offer only one grade, the eventual switch from 100LL may need to occur on a coordinated date rather than through a gradual phase-in.
Cost, Compatibility and Supply Remain Open Questions
The plan identifies cost, liability and schedule as the unleaded avgas transition’s principal risks. Aircraft owners could face expenses for STCs, mechanic labor or hardware changes, while airports may need changes to storage and dispensing equipment. Fuel producers must also develop enough capacity to replace roughly 180 million gallons of annual 100LL demand.
“A successful transition must preserve the reliability, safety, and accessibility that pilots, aircraft owners, service providers, airports, and communities depend upon every day,” EAGLE industry members said in a statement included in the plan. “The plan acknowledges challenges going forward with such issues as fuel compatibility and commingling, storage and distribution infrastructure, liability concerns, regulatory clarity, and possible aircraft and engine modifications.”
Alaska presents a more unique challenge for rolling the plan out. Much of the state’s avgas arrives through seasonal bulk deliveries, and many remote locations utilize just one storage tank. The FAA recommends beginning coordination for Alaska’s full annual unleaded avgas volume about 24 months before the December 2032 deadline. Phase 4’s actual milestones will depend on fuel selection, aircraft alterations, storage limitations and experience gained during the national transition.
The FAA expects to begin rulemaking during Phase 2 to establish unleaded avgas standards and provide the full regulatory framework for ending leaded-fuel sales. Many of the details that will determine the unleaded avgas transition’s effect on aircraft owners remain unresolved, including fuel prices, required aircraft modifications, compatibility among competing fuels and replacement-fuel availability away from an aircraft’s home airport.
FAA Deputy Administrator Chris Rocheleau described the 2030 unleaded avgas mandate as “aggressive” during a Meet the FAA Administrator forum last week at AirVenture.
“I can tell you with confidence we’re not going to set an arbitrary date that says, ‘well, this is what it says,’ without making sure that whatever we’re going to put in those aircraft is safe,” Rocheleau said.
This early reporting represents a first-pass look at the new unleaded avgas transition plan, and there is still more to be learned. AVweb will continue reviewing the plan in order to provide a deeper analysis for pilots, aircraft owners, airports and fuel suppliers soon.
This program the FAA is putting forward is just not workable and they all know it but that’s why it is good to have government job where you keep you job when performing this poorly.
The FAA actually started to follow a path that would have created results. They realize that Europe was making progress to get rid of the lead with their program which allows ASTM approved UL 91 to be used without an STC in most Aircraft. To follow that idea the FAA was going to give a fleet approval for ASTM approved UL 91 in the United States, but they did not follow through.
A two tank solution is probably the only way we will see real results that get us off the Lealed Fuel. Because of the nature of the this type of fuel, different octane levels should be available, depending on the engine. Cars offered different octane levels of fuel because of that. Considerable savings can be achieved by using the octane level that is most appropriate for an engine.
With the current one tank solution the FAA has chosen for us, it will require aviators to purchase very expensive fuel that most Aircraft engines really don’t need. Currently by blocking the Two tank solution the FAA is effectively damaging the progress toward transitioning off of leaded Fuel.
I talked to a Swift fuel rep at EAA AirVenture. Asked if we would have unleaded fuel before we all go electric.
Keep in mind that while “most” aircraft do not require 100 octane fuel, “most” of the aviation gasoline sold is dispensed into aircraft which do require 100 octane fuel. Arguing that since most aircraft do not require 100 octane fuel that the availability of 100 octane is somehow not a priority is a disservice to the avgas using community.
All this once again proves the Limbaugh theory to be accurate: Everything the government touches, turns into a mess. Zero regulation of anything always leads to lower costs, more choice, and a growing economy. The number one producer of piston aircraft engines in the world is Rotax. The preferred fuel for their engines is ethanol-free, lead-free, auto fuel, available everywhere - but California, of course.
Rotax engines will run on E10 if ethanol-free is not available and Rotax would prefer using E10 over 100LL The main problem with E10 is that the ethanol will evaporate so it does not store as well as ethanol-free fuel. I am not familiar with California fuel availability. Is ethanol-free not available in California?
You are correct, however Rotax will tell you to avoid leaded fuel and ethanol-free if possible for all the usual reasons - corrosion, less energy, lower fuel economy, water absorption, etc. California has essentially banned the sale of E0 within its borders, go figure. It is an “ethanol free desert” within a country with currently 19,928 sellers of E0, according to pure-gas.org. Ethanol’s biggest problems are (a) it absorbs moisture and creates a highly-corrosive substance, (b) it contains only 70% of the energy by volume as good old gasoline. The only reason it is in our fuel is due to the horrible EISA 2007 law that forces gasoline sellers to mix it into our fuel. E0 is what is available at all fuel terminals, as ethanol may not be send through pipelines due to its corrosive properties.
I have never read so many people beating around the bush! The issue is; exhaust valve burning; what will prevent exhaust valves from burning over 3000 hours of flight? Leaded Avgas will do this. Anything else? Nothing that I have seen or read, yet! I heavy non toxic metal, other than lead, is probably required; steel fillings, copper fillings, are the two obvious. Though copper is likely to stick to the exhaust valves over time; leaving steel! Maybe nickel. Must be non toxic! No one has even tested any of these obvious solutions! Just ridiculous so far! And in the same quantities in avgas as lead; up to 25 PPM? Though, during the 1970s, the EPA demanded lead levels in avgas be reduced to 5 PPM, I believe! And since there are only around 200,000 certified aircraft and the their engines, spread over the entire US; where is the problem? There is none. If ever a problem has been made up, it is this one! Maybe at Van Nuys, the busiest general aviation airport on Earth; maybe! I believe and hope the FAA is monitoring lead levels around Van Nuys to know what has settled on the ground, next to the runways, 10 feet from the runways, a quarter mile from the runways, and a mile from the runways. And what lead levels are in the air around Van Nuys over the same distances from the runways. And what ever these numbers are: divide by them by 100 to 1000 for all other airports, I would say! Or, no lead problem anywhere else! One large volcanic eruption puts more lead in Earth’s atmosphere than all of the aircraft on Earth; another reason why this is not a problem! Considering all relevant, I repeat all relevant facts matter; and has never happened regarding lead in avgas! Environmentalists are like rabid dogs, they get a bone and will not let go, no matter what! One would think the FAA would have the above figured by now, but if they have, I have not seen it in writing anywhere! Very regrettably!
Complete debacle. If a gut feeling tells you anything, this comes through in spades. Virtually every plane will require an STC? It won’t be like having an STC for some known hardware where the effect on the airplane is immediately obvious and has no reason to change over time. No, once airplanes roll out of the factory, all kinds of things happen to them over decades of use, different equipment and configurations, some components very old, some new, some covered by OTHER STC’s, even some installed via FIELD APPROVALS from long ago where fuel plays a role. Knowing how many configuration variations of the same models of airplanes exist is like asking how many shades of gray exist. IMO, some airplanes that are perfectly legal to fly today with 100LL are going to fall through the cracks of an impossible effort to determine the safety of flying with unleaded fuels. On the other hand, what if it is actually determined up front that a particular airplane, again safe to fly today with 100LL, cannot reasonably be converted to fly with unleaded fuel? That airplane instantly assumes the value of a brick and the owner assumes the loss? Aside from the possibly argument that companies will, at some point, just not want to continuing to manufacturing 100LL, the rest of this push to make the change is agenda driven. I think most of us know it.