The Baron is being used as a test bed to compare the performance of General Aviation Modifications Inc.’s (GAMI’s) G100UL unleaded avgas with 100LL. The stains are on the wing with the tank holding G100UL, but it has not been determined that they came from the fuel.

• READ MORE: GAMI Responds to Cirrus G100UL Service Advisory

“We have scheduled a mechanic to determine the cause of the leak coming from the left wing of the Baron, which should happen in the next few days,” AOPA senior vice president for media Kollin Stagnito told AVweb. “We are not yet sure what the substance is, nor where it is coming from.”

Word of the stains has been a hot topic on various forums, and speculation is rampant as to their cause.

• READ MORE: Unleaded Fuel Debate Heats Up in Oshkosh

GAMI chief engineer George Braly told AVweb the cause is most likely a faulty or improperly installed fuel cell bladder or patch inside the bladder. Braly said the bladders in the Baron may be more than 40 years old. He said G100UL has been tested for compatibility with the bladder material and there were no problems. He also added that fuel bladder leaks are a relatively common issue with Barons.

Editor’s Note: This article first appeared on AVweb.

The post Stains Reported on Wing of AOPA Aircraft Fueled by GAMI G100UL appeared first on FLYING Magazine.

During the public comment period after formal presentations, Tim Roehl, president of General Aviation Modifications Inc. (GAMI), challenged a couple of points made during the presentations of members and support staff from the End Aviation Gasoline Lead Emissions. He told the crowd—smaller than in previous years—that contrary to assertions made during the formal part of the forum, GAMI’s G100UL is indeed ready for distribution and sale.

Eliminate Aviation Gasoline Lead Emissions (EAGLE) initiative member Pete Bunce, president of the General Aviation Manufacturers Association (GAMA), stood up and dismissed Roehl’s assertion.

“I totally disagree, but that’s a discussion for another day,” said Bunce.

• READ MORE: GAMI’s G100UL Unleaded Fuel Successfully Powers Historic WWII Aircraft

In earlier comments, Bunce said his organization remains adamant that any new fuel will be approved through “transparency and a peer reviewed process,” which has traditionally been done through ASTM International.

“Transparency is so absolutely vital for us,” said Bunce.

Refiner Vitol Aviation has 1.3 million gallons of G100UL in tanks in Louisiana and says it has been completely vetted as ready for sale through its supplemental type certificate (STC). GAMI and Vitol have consistently said the FAA approval of an STC covering all gasoline engines on the agency’s registry satisfies all the regulatory and safety requirements to begin retail distribution of the fuel, but there are critics who contend it needs a consensus standard determined by an independent organization like ASTM to satisfy concerns about materials compatibility.

Aircraft Owners and Pilots Association (AOPA) president Mark Baker said his organization is using G100UL in a Beech Baron it operates and, based on the 200 hours of experience with the fuel, “GAMI is as good or better” than 100LL. He also said the process has to “move forward” to get the correct fuel.

• READ MORE: Cirrus Service Advisory Throws Fuel on G100UL Maintenance Debate

The balance of the meeting was a reiteration of the stated goals of EAGLE, which increasingly has become focused on maintaining the supply of 100LL. The existence of the commercial quantity of G100UL has prompted politicians in California and Colorado to try to ban 100LL in favor of filling airport tanks with G100UL. Legislative and legal initiatives in both states are moving through their respective processes.

Meanwhile, testing of the last remaining candidate under the congressionally mandated Piston Aviation Fuel Initiative (PAFI) is slowly progressing at the FAA’s Atlantic City, New Jersey, test facility.

About 23 percent of materials compliance testing, 25 percent of durability testing, and a few percent of several other categories have been done on Lyondell/Basell/VP Racing’s entry. It’s also been fully tested on the airframe of a Lancair Legacy and on a Continental TSIO 550K engine.

Editor’s Note: This article first appeared on AVweb.

The post Unleaded Fuel Debate Heats Up in Oshkosh appeared first on FLYING Magazine.

The aircraft took off from Ada Regional Airport (KADH) in Oklahoma and flew over Lake Atoka during the 60-minute flight. According to GAMI, the warbird’s 2,000 hp Pratt & Whitney R-2800 Double Wasp engine is the most powerful to fly on the G100UL fuel.

• READ MORE: GAMI Responds to Cirrus G100UL Service Advisory

“This big-bore radial engine operating at up to 48-inch MP demonstrates the excellent high-octane performance of the G100UL high octane unleaded avgas,” GAMI said in a statement. “The ability to successfully operate this engine as such on an unleaded fuel supports the continued operation of these and many other warbirds well into the future.”

Editor’s Note: This article first appeared on AVweb.

The post GAMI’s G100UL Unleaded Fuel Successfully Powers Historic WWII Aircraft appeared first on FLYING Magazine.

The issue of what is legal (in FAA terms) and approved (by manufacturers) puts maintainers in a sticky situation. On one hand, the FAA issues a supplemental type certificate (STC) allowing for products to deploy on aircraft, but the engine and/or aircraft manufacturer may not approve or recognize the STC as something permitted for use under the terms of their warranty. 

Whether an aircraft owner or operator chooses to use the alternate fuel or not is a matter of choice. The fuel has been approved by the FAA and is perfectly legal to use in the SR series aircraft. The dilemma for the maintainer arises upon returning a Cirrus aircraft to service even for something as routine as an oil change. 

• READ MORE: Identifying Corrosion in All Its Forms

Consider this scenario. The pilot opted to refuel with G100UL or the aircraft arrived with G100UL in the tank. This alternate fuel is a drop-in replacement, so 100UL could have been added to 100LL already in the tank. Granted the maintenance action in this case did not involve fuel, but the maintainer is signing for the entire aircraft to be returned to service. If they sign the repair IAW OEM guidelines, this includes Service Advisories (including one that prohibits the use of G100UL fuel). Consequently if the aircraft is carrying G100UL, then this could be an issue because the aircraft is not being returned to service IAW this Cirrus SB.

Of course, as with any guideline, the issue of signing for an aircraft is subject to interpretation. I know mechanics that will only work on aircraft they have personal history with and do not want to return to service an inherited unrecognized maintenance action.

In the advisory (SA24-14) “Transition to Unleaded Fuel and Use of Non-Cirrus Approved Fuel in SR Series Aircraft” released June 18, Cirrus said it was committed to the industry’s transition to unleaded fuels, which is underscored by its collaboration with stakeholders such as the Aircraft Owners and Pilots Association (AOPA), General Aviation Manufacturers Association (GAMA), FAA, and Eliminate Aviation Gasoline Lead Emissions (EAGLE) industry initiative.

Aircraft and engine manufacturer’s are extremely risk averse. They historically do not recognize alternate methods of airworthiness, and this includes STCs, parts manufacturer approval (PMA) parts, and designated engineering representative (DER) repairs.

There is a commercial element to this since any aftermarket PMA part procured from a third party is a revenue lost for the OEM. It appears the reason for the SB in this specific case is Cirrus’ concern about the breakdown of a fuel tank sealant that was seen in an isolated (one) aircraft known to have been fueled with G100UL.

The company will need to vet this against other aircraft in the fleet to ascertain if the perceived breakdown is an isolated outlier related to the drop-in fuel, or if the dislodged fuel tank sealant was a manufacturing defect unrelated to the use of G100UL. 

• READ MORE: 5 Attributes of a Top-Notch Maintenance Provider

“While some aspects of the initial Cirrus testing of the GAMI G100UL fuel are encouraging, other areas, including materials compatibility, remain inconclusive,” the advisory said. “At this time, Cirrus does not approve the use of GAMI G100UL fuel in Cirrus SR Series airplanes. Per Continental and Lycoming, only approved fuels may be used for an engine to be covered by warranty.” 

According to the FAA, G100UL is safe to use, hence the STC approval. This took years of testing to clear the milestones. In fact GAMI uses the fuel in its company SR22..

According to GAMI, the fuel has undergone substantial testing and displayed no issues on other aircraft. The company also disputes Cirrus’ claim that using G100UL voids the warranties on engines supplied by Lycoming and Continental, however, the engine manufacturers have confirmed its use could affect warranty claims, according to AVweb. 

Tim Roehl, president of GAMI, indicated that his team is drafting a formal response to Cirrus Service Advisory SA24-14 to be posted on its website. Roehl also said that the sealant Cirrus references is not the polysulfide sealant more commonly used in the industry but a polythioether sealant. Roehl stated that G100UL has been in service since 2010 on one wing of the company’s Cirrus SR22, using the same polythioether sealant Cirrus uses, with zero incidents.

The FAA does not comment on specific OEM warranty policies but the agency has reiterated that GAMI’s G100UL does have the STC approval. This is not uncommon as the FAA routinely approves alternate solutions without the buy-in from OEMs. The burden is on the third-party solution provider to prove airworthiness—i.e. STC holder, PMA manufacturer, or designated engineering representative for DER repairs.

What This Means for Maintainers

This fuel issue places aircraft maintenance professionals in a bit of a quandary. On one side, you have the FAA approval for G100UL, but at least one aircraft manufacturer, Cirrus, and one engine manufacturer, say they are not approved via service advisories.

The FAA typically steers clear of airframe/powerplant OEM issues until they become an airworthiness directive (AD). To assist in clearing any confusion, the agency issues periodic documents to help owner/operator/maintainer stay abreast of the situation. One such publication is the FAASTeam service bulletins.

When asked if service bulletins are mandatory, the FAA says: It depends. 

Here is a quick agency ruling: “If you are operating your aircraft under 14 CFR part 91, a service bulletin is advisory, and compliance is not mandatory unless it is included in an Airworthiness Directive.”

Another resource is FAA Advisory Circular AC 20-114, which addresses manufacturers’ service documents: “Service documents should be neither treated nor represented as the official FAA approval documents, unless either a letter of design approval from the FAA or a record that compliance has been determined by an FAA designee is on file for recommended actions indicated as FAA-approved in service documents.”

That said, service documents are beneficial and transmit a wealth of knowledge. When returning aircraft to service, it is critical to list if the action is in accordance with OEM information or another alternate form of maintenance. This comes into play when installing PMA parts, or an STC like G100UL.

The post Cirrus Service Advisory Throws Fuel on G100UL Maintenance Debate appeared first on FLYING Magazine.

More importantly, according to Braly, after testing the fuel received a certificate of authenticity (COA), which then makes it “commercially available.”

• READ MORE: Long-Term Unleaded Fuel Test Begins in AOPA Baron

With the announcement, Braly and GAMI hope to counter critics that say while the fuel has received FAA approval for use under the STC process, it’s not commercially available. The term is important because of a consent decree taken in California that could force the changeover to an unleaded fuel when an alternative to 100LL becomes commercially available.

• READ MORE: G100UL Unleaded Avgas Flight Trial

Editor’s Note: This article first appeared on Kitplanes.

The post GAMI Says It Has 1 Million Gallons of G100UL appeared first on FLYING Magazine.

In this video, The Aviation Consumer’s Larry Anglisano Zoomed up with Audio Authority founder and CEO Jon Sisk, who recently conducted an exhaustive G100UL flight trial in his Lycoming-equipped Van’s RV-14, White Lightning. Sisk made side-by-side engine data comparisons burning G100UL and 100LL and reported his findings, while offering some advice on how you can add this approved fuel to the aircraft’s published operating limitations.

Editor’s Note: This video was produced by Aviation Consumer magazine.

The post Aviation Consumer Live: G100UL Unleaded Avgas Flight Trial appeared first on FLYING Magazine.

The project launched this week with the introduction of GAMI’s G100UL during initial flights in Ada, Oklahoma. Beginning with a baseline of two freshly overhauled Continental IO-520 engines, the Baron will be operated under AOPA management, with the cooperation of Savvy Maintenance founder and technician guru Mike Busch, using the company’s computerized diagnostic tools to analyze engine data and compare it against the information it has collected from “hundreds of thousands of hours of GA flights,” according to an AOPA release.

• READ MORE: Time to Get Serious About Unleaded Fuel

An AOPA spokesperson told FLYING that the association is staging in Ada right now “since that is where the majority of the fuel is, and it makes sense to use [it] as a geographically appealing hub.” Presumably this will allow AOPA the “best efficiency in demonstrating the fuel to a wide range of people.” GAMI’s fuel obtained a supplemental type certificate, covering a broad range of piston aircraft, from the FAA in September 2022. The initial STC for Lycoming O-320, O-360, and IO-360 engines came in July 2021. 

• READ MORE: GAMI Gaines Avgas STC for Pistons on Unleaded Fuel

AOPA president Mark Baker was at the controls for the demonstration flight to kick off the program on October 31. For one hour, Baker flew with G100UL feeding the left engine and standard 100LL powering the right one.

“We wanted to get some actual experience with a 100-octane unleaded fuel in the kinds of airplanes and engines that our members own and fly,” said Baker. “This fuel has been tested extensively in labs and received an FAA STC. Should the FAA approve additional fuels, we’ll test them, too, so we can see what they’re like to use out on the airways.

• READ MORE: GAMI Now Selling STCs for G100UL

“George Braly and GAMI have done a great deal of pioneering work preparing for general aviation’s unleaded future. We’re staging the AOPA Baron at GAMI’s headquarters in Ada first to try out its G100UL.”

The post Long-Term Unleaded Fuel Test Begins in AOPA Baron appeared first on FLYING Magazine.

Because of the way the U.S. government operates, particularly under the Clean Air Act of 1970, certain processes within the associated agencies, including the FAA, could not begin without the finding.

Now leadership from within the industry’s manufacturers, distributors, associations, and users (that’s us, the pilot community) can act on the commitment to getting the lead out of our avgas—specifically the high octane fuel required by high-performance piston engines currently served by 100LL.

But what happens now? I spoke with Walter Desrosier, vice president of engineering and maintenance for the General Aviation Manufacturers Association, this week about the finding and what it triggers. “We have significant progress,” said Desrosier. “There is a broad, collective community commitment from the entire GA industry in cooperation with the government and the FAA to move to no lead. So the EPA action that came out is part of that transition process. It actually puts into the Clean Air Act process how they will mandate a transition. So this is not something that we continue to talk about, that we hope to find solutions—this is a commitment  from the industry that continues to work towards the best solutions.”

The timeline has officially begun, but it will take a couple of years for the mandate and the associated guidance to come into play. In the meantime, the industry is already working hard toward fielding the solutions.

Fuels in Process

Those solutions include four candidate fuels in the works from different providers in varying states of development, testing, and acceptance. “Part of our transition will also be what’s the best available fuel,” said Desrosier.

By most measures, the furthest along comes from GAMI Inc., whose G100UL has attained supplemental type certification from the FAA. GAMI works with at least one producer, VTOL, to manufacture the fuel in enough quantity to reach those who need to test it and develop its distribution in the field. The STC means the FAA considers the fuel safe for the applications covered in that approval.

While the STC includes broad fixed-wing piston aircraft acceptance, testing continues for rotorcraft with Robinson deep into its program with the fuel. Cirrus Aircraft is also testing the fuel within its fleet.

But any fuel that makes it to market must also demonstrate commercial viability. It must make it from the manufacturer through the distribution channels—pipeline or trucking—to the airport where it goes into a tank, and then into our fuel tanks on aircraft. That means the fuel must be acceptable in each of those steps by the businesses involved, as well as the end user burning it in flight.

“With the GAMI fuel, the path that they chose to take is to do their proprietary STC approval, which is perfectly fine on the safety side with the FAA, but they also chose not to enter into an ASTM consensus specification process,” said Desrosier. “Typically that’s how all the other stakeholders in the community become familiar with a fuel…the content of the fuel, the understanding of the evaluation and the assessments of the fuel, and the understanding of the components, and the understanding of the business risks related to being a stakeholder who might purchase, who might produce, who might distribute, who might dispense, and who might put it into people’s tanks.

“There’s a lot of business decisions in this, and a lot of risk.”

Swift Fuels has already entered the market with a lower octane unleaded fuel, 94UL, with limited distribution now but a growing foothold, especially in states and at airports where there is more pressure to get away from leaded avgas.

Swift is pursuing both an STC and ASTM path with its high octane fuel, 100UL, and it has chosen a clever way to gain market acceptance—and perhaps reach commercial viability—with the new fuel. For its current 94UL, Swift offers a “Forever STC,” through which an operator purchasing the STC for the lower octane fuel is promised that the STC for the 100UL fuel will be  included in that purchase when it’s available.

Swift will be able to deliver the fuel through the existing infrastructure to the existing tanks it has put in place for 94UL. According to Desrosier, Swift has already started the consensus standard and is going through the STC process. Critically, the manufacturer will share the results through the consensus process, and when it obtains FAA approval, it will share that data with all the stakeholders.

Two other fuels are pursuing approval through the PAFI (Piston Aviation Fuels Initiative) program. One already has the ASTM test specification, produced by Afton Chemical/Phillips 66, and it is continuing to share information, according to Desrosier. It has to go through the full ASTM testing process, but it has “the roadmap” to do it.

The other candidate fuel (Lyondell/VP Racing) is close behind. The consortium has entered into the specification process and expects to also share its progress.

More than One?

One big question in my mind: Will we end up with more than one fuel, and will they be intermixable? I asked Desroiser, along with the follow-up question: Is this testing pathway defined or is it wait and see?

No, said Desrosier, the fuels are not allowed to intermix and co-mingle. All of the candidate producers are testing to comingle with 100LL—because that is part of the transition process and very likely to occur in the field.

“In terms of ‘could be,’ it depends on the final composition of the fuels,” he said. “We do know some of the key components,” and some fuels will not be able to mix because they are too different.

In the end, having two fuels make it through the process means that the market will decide—and we will have a backup in case of an unforeseen issue with a producer or fuel. “We think it’s going to have to be a market decision,” said Desrosier. “I’m not expecting a significant market penetration, dividing the market in half” with different fuels regionally available.

“Once you have the acceptance by FAA, ultimately the consumer is the very last in the supply chain,” he concluded. 

With the pilot or owner-operator, it often boils down to price—and that won’t likely change with 100UL.

The post Time to Get Serious About Unleaded Fuel appeared first on FLYING Magazine.

EAGLE—which stands for Eliminate Aviation Gas Lead Emissions—includes partners from aviation industry associations, the FAA, fuel producers and distributors, airport operators, and local community and environmental experts. With the aim to transition away from leaded avgas—100LL—by 2030, EAGLE has the twin missions of supporting development of replacement fuels and advocating for the continued supply of current fuels until the OEMs, operators, and pilots feel secure in the safety and security of the new fuel source(s).

It’s a tall order. Though four entities reported significant progress with their specific candidate fuel, there are varying degrees of confidence in both the composition and distribution prospects of each one.

The EPA’s Next Step Lies Ahead

And time is of the essence—though it’s not prudent to panic yet, according to leaders like Chris D’Acosta, founder and CEO of Swift Fuels, which is currently working on one candidate fuel. What would trigger that response? The Environmental Protection Agency announced its proposed endangerment finding on leaded avgas last October, and it stands to finalize that this October, on schedule.

What does that mean? It doesn’t mean that leaded avgas will be banned immediately. At the briefing, General Aviation Manufacturers Association (GAMA) president and CEO Pete Bunce outlined the steps that would follow the finding. “The people that have to implement the rules are [at] the FAA,” said Bunce of the next steps following the endangerment finding. “There’s a very structured process.” He estimated that there would be about two or three years to completely field the transition fuel. That’s part of the reasoning behind the 2030 goal EAGLE set, to work through this “very methodical process.”

“We have smart people working in these four companies, and we’re going to have a solution,” said Bunce.

• READ MORE: UND Aerospace Transitions Full Fleet to Unleaded Avgas

Four Fuels

Representatives from each of the companies or partnerships working on those fuels presented their progress, starting with D’Acosta. 

Swift Fuels

Eight years ago, Swift Fuels began delivering the first batches of its UL94 unleaded avgas, and it can now be found in roughly 81 locations across the U.S. The current fuel serves as a drop-in replacement for 130,000 aircraft on the registry—for which FLYING awarded Swift its 2023 Innovation Award. The success of UL94 sets the stage for its higher octane 100R fuel that will serve the remainder of the GA fleet. Swift followed a dual certification program with UL94, acquiring ASTM acceptance as well as supplemental type certificate approval from the FAA. It is pursuing the same path with 100R.

Swift offers a “forever STC” that covers the UL94 as well as future fuels, along with all of the placarding and any changes in documentation. The underlying goal is to establish a sense of security among those who will put the fuel into their tanks—both at the airport and on the airplane. “The emotional uncertainty at this time is really counterproductive to everybody’s interests,” said D’Acosta.

GAMI

George Braly of General Aviation Modifications Inc. presented next, reporting on the nearly 14 years since GAMI began development on its unleaded avgas replacement—and culminating with the issuance of its blanket STC for all aircraft powered by spark-ignition engines in September 2022. “GAMI has fixed the problem,” said Braly, summarizing what had been the general feeling at the time of the STC’s debut. GAMI is working with OEMs like Robinson (for rotorcraft implementation) and Cirrus in its SR22T, considered one of the most complex powerplant installations to accept the new fuel. 

While the STC has been available for nearly a year, GAMI is still struggling to supply the fuel to the market. To this end, Braly announced it had partnered with “an extremely large producer of aviation jet fuel,” VTOL, to produce the G100UL in quantity. That Houston-based company has finished its 4 million-gallon tank toward making that happen.

LyondellBassell and VP Racing

Two of the fuel developers are pursuing approvals through the Piston Aviation Fuels Initiative (PAFI), established by Congress to achieve fleet authorization through a collaborative industry-government process. LyondellBassell/VP Racing is the first of these. VP Racing is a Texas-based developer of fuels and additives for the automotive racing industry, and LyondellBassell produces high-octane lead components for automobiles. In his remarks at the briefing, Dan Perot of LyondellBassell admitted the partnership was “relative latecomers to this race,” as it started in 2018 to develop its answer to the high-octane avgas question.

“We chose to stay with the PAFI program despite delays during the COVID period,” said Perot, “because we felt that it provided the best mechanism for us to learn what the industry needed, communicate with the FAA and OEMs, and secondly, and maybe most importantly, it required ASTM certification for the fuel.” 

According to Mark Walls of VP Racing, the partnership’s fuel meets all D910 specs, is of the same density as 100LL, and is poised to be cost-competitive. The company is about to enter “full-scale” testing after preliminary work in Lycoming and other engines. Like other fuels in development, Walls said its avgas is fully compatible with 100LL in case of mixing in aircraft tanks.

Afton Chemical and Phillips 66

The second partnership pursuing PAFI-based authorization is between Afton Chemical, headquartered in Richmond, Virginia, and Phillips 66. The pair are also working on new lubricants to accompany the high-octane unleaded fuels. Enrico Lodrigueza with Phillips 66 updated on its progress, detailing the candidate fuel, which uses manganese—a coenzyme used in the human body to break down carbohydrates and proteins, a transition metal—to replace the tetraethyl lead in 100LL. The fuel has an ASTM specification in place, ASTM 28434, according to Lodrigueza, which is “substantially similar” to the D910 spec for 100LL.

Lodrigueza characterized the manganese-based octane booster in use. “Manganese is not a heavy metal. That’s one major difference…it’s an essential nutrient.” As far as testing, the partnership has had “a lot of vetting” by subject matter experts and is ready to proceed with detonation testing at the Tech Center on a Lycoming engine. As with all of the potential replacement additives, close scrutiny is being placed on what issues may occur with the new element in the fuel, such as spark plug fouling. The lubricants testing will also ensure compatibility with whatever oil is in use, for example.

What’s Next?

Clearly, the four candidate fuels are in different states of availability for testing—some more broadly than others—and both the engine and airframe OEMs are eager to keep going. Bunce summarized the position of the manufacturers. “We have the money, our manufacturers have the money to purchase it, to be able to go and look at that fuel and understand what chemical components are in relation to the spec to be able to run it and to do the type of testing that we feel comfortable that we can put our families into that aircraft employing that fuel. And if we see good or bad, we will share it, as manufacturers, to the FAA., That’s our obligation—but that’s the right thing to do.”

The post EAGLE Initiative Shows Measured Progress, Fuel Contenders Say at Oshkosh appeared first on FLYING Magazine.

To focus a lens on the issue—and compel critical questioning to the process—the General Aviation Manufacturers Association on Monday hosted a roundtable of stakeholders to the EAGLE (Eliminate Aviation Gasoline Lead Emissions) initiative to give an update on how things stand. The initiative seeks a complete replacement of leaded fuel by no later than 2030, with a sunsetting of the fuel while maintaining a high level of safety in GA operations, which it primarily affects.

The panel was led by the co-chairs of the initiative, Mark Baker, president and CEO of the Aircraft Owners and Pilots Association, and Lirio Liu, executive director, aircraft certification service for the FAA, and supported by leaders from the National Business Aviation Association, National Air Transportation Association, Experimental Aircraft Association, Helicopter Association International, and the National Association of State Aviation Officials.

Leaders from four key manufacturers with a front-row seat to the sunsetting of leaded fuel joined them with their input on the state of affairs:

• John Calcagno, president and CEO, Piper Aircraft
• Ron Draper, president and CEO, Textron Aviation
• Patrick Horgan, president and CEO, CubCrafters
• Shannon Massey, senior vice president, Lycoming Engines

The urgency is real: The Environmental Protection Agency released its proposed finding on leaded aviation fuel in October 2022, setting the stage for a final ruling that industry leaders expect to occur by the end of 2023.

Getting to Approval

At the moment, four candidate fuels are in the process of development and testing. However, they are taking two different pathways to achieve that goal. 

The first is based on the FAA’s long-running Piston Aviation Fuel Initiative (PAFI) program and utilizes consensus standards developed in concert with the American Society of Testing and Materials (ASTM). This was the process completed by Swift Fuels with its UL94 unleaded avgas that came into the market in earnest starting in 2015 and reaching widespread use as of 2021. Two entities have 100-octane fuel in the evaluation process under PAFI: Afton Chemical/Phillips 66 and Lyondell/VP Racing. 

“Currently, the PAFI fuels are completing full-scale engine durability and endurance testing, which is expected to complete by the end of July,” according to Peter Bunce, president and CEO of GAMA. When a fuel passes the next gate of testing, it will proceed onto the next level with airframe OEMs. Completion of the ASTM process will allow entry into the market with a high degree of confidence in its suitability.

The alternate path is through the supplemental type certificate (STC) process, which is proprietary to the fuel manufacturer working directly with the FAA. Two STC fuels are currently using that process for approval—Swift Fuels’ 100R and GAMI’s G100UL. Swift Fuels also plans to go through the ASTM acceptance for its high-octane fuel and, according to GAMA, ASTM already has a task committee set up to evaluate the fuel.

GAMI has received FAA STC approval for use of its fuel in a wide range of powerplants, and owners can purchase the STC for their aircraft now. However, the fuel is not yet available in the market. According to GAMI, the fuel will be available “as fast as production can be ramped up and fuel can be delivered to airports. It has been estimated that 2023 will be a year of logistics with G100UL avgas appearing more widely in 2024. The first customers for the fuel are likely to be flight schools.” 

Cirrus is currently testing the GAMI G100UL in its fleet, and other OEMs stand ready to do so, but the process is more incremental—and less transparent as a result of its proprietary nature.

Octane Is Only One Metric

Lycoming’s Shannon Massey delivered her comments, representing the more than 100,000 powerplants that the aviation engine OEM has shipped in its 95-year history—with more than 650 type certificates for the various models in the field. These are in addition to the engines powering experimental aircraft.

More than half require high octane fuel, according to Massey. “(They are) the workhorses of the fleet. They are ferrying supplies to remote locations. They’re patrolling borders. They’re supporting military operations….The loss of the ability of these airframes to serve society would definitely be impactful, which is why we, as an OEM [and] engine provider, are looking to make sure that we know—under unleaded fuels and the development that’s taking place in those—what are those key characteristics?”

Massey called for greater involvement in the process, regardless of which fuel was making its way through the gates—and which pathway to approval was pursued. “We need to ensure that whether it’s through industry/government—the PAFI authorization process—or be it the supplemental type certificate (STC) process, that we have a good understanding and knowledge of the specific tests, and which models of engines are evaluated. So that way we can stand behind that portion of it.”

However, getting a fuel to a required octane level is only one of the metrics needed in bringing it to the market successfully—and safely. Massey outlined seven elements that Lycoming seeks answers on, which were echoed by other stakeholders on the panel.

Toxicity

In the quest for a higher-performance fuel, aromatics—chemical compounds (hydrocarbons) that increase octane—replace the tetraethyl lead (TEL) present in 100LL. However, many are known to also be carcinogenic, such as benzene and toluene, and their use is limited in gasoline in many countries. “So we don’t want to replace one fuel for another one that’s going to be harmful, whether it be to the environment or the public,” said Massey.

“We need the transparency of the chemical composition of each fuel to be evaluated by some government entity to give the industry a thumbs-up or -down that what is put into the atmosphere when the fuel is burned is not likely to be a significant concern now or in the future to be harmful,” said Bunce in a follow-up with FLYING. “This is why we encouraged the FAA to have either EPA or some other government entity assess the components of all new fuels to give the industry their expert judgment and green light to move forward. If the EPA won’t do it, then I think the FAA’s choice of the National Academy of Sciences to pull together an expert panel is a good alternative.” There is concern that one or more of those compounds may be in a candidate fuel—but this cannot be confirmed without transparency to the makeup of that fuel.

Materials Compatibility

An engine doesn’t stand alone—and it too is made up of a myriad of parts and components. Of particular concern to Lycoming, as well as airframe OEMs, are the effects that a new fuel will have on other materials used within the powerplant—such as O-rings and seals—as well as the fuel system and other accessories within the airframe tying the tanks to the engine and sending the byproducts out through the exhaust. 

Original testing of early unleaded fuels bears out this concern. Ron Draper of Textron Aviation said in the briefing, “We have tested fuels in the past that have a similar but different recipe, and we had some results that were…I guess, less than desired. In the past, some of those fuels did have wear and tear on soft materials in the airplane—O-rings, gaskets, hoses, bladders, sealants—and we’re unsure of these new fuels, what (they’re) going to do to the engine, what it’s going to do to the airplane.”

Stability

In order to survive production, storage, transportation, tankering, and extended time within FBO and aircraft tanks, a fuel must be stable. It cannot degrade quickly or harm the containers in which it is kept, to a certain extent. Corrosive properties may impact the metal or other materials in the engine or airframe as fuel sits within them over time. The octane may also degrade over long periods.

Vaporization

The distillation curve is another concern. “Fuel’s ability to vaporize at any given temperature—that’s key if we’re looking for ‘startability,’ ‘runability,’ and [addressing] vapor lock concerns,” said Massey. These are not engines or aircraft that can work 99 percent of the time, as was pointed out by John Calcagno of Piper Aircraft.

Density

Another aspect of a new fuel most may not have considered is a difference in density affects a number of things, including the fuel’s overall weight. Aromatics used in unleaded fuel tend to be denser, potentially increasing the fuel weight. Remember the rule of thumb to use 6 pounds per gallon of 100LL in weight and balance calculations? That may change with the new fuels. It may also affect center of gravity, seeing as how most fuel tanks are positioned near the aircraft’s CG—but not all are.

Fuel Controls

A sixth aspect to take into account is any change in the fuel’s volume and how that might affect the metering. “Fuels with increased density will exhibit higher mass flow rates,” said Massey, “and thus higher fuel-to-air ratios.” So, fuel controls would have to be adjusted to accommodate a denser fuel—and keep operations predictable and safe.

Repeatability

The final key noted by the panel is the ability to repeat the fuel recipe by way of a mature production specification. Massey concluded: “These are all considerations that without us having the knowledge base and being able to characterize and/or standardize the testing methods, what does that mean and how does that impact our current (engines) that are out there?”

What’s Next?

FBOs stand ready to accept the fuel—whatever reaches the market first—once accepted and approved. But the market seems to think high-octane fuel should already be out there. Curt Castagna of NATA reported, “Historically, aviation fuels sold as a commodity [are produced] and delivered to the airports and FBOs through the fuel distribution network, where those entities are relying on today the four major fuel suppliers that are delivering that fuel, to bring them a fuel that has, for the last many decades, met an ASTM standard.”

A mature production specification is needed, then, to get unleaded avgas into the market in real quantities—but the perception is running ahead of reality. Castagna said, “There [are] expectations by the users that are buying fuel today—FBOs and airports are hearing from both their user constituents and then their ‘outside-the-fence’ community interests” that are looking to see lead removed.

“All of us here today in the industry are unified in removing that lead—it’s how do we get there?” Castagna concluded. 

While the next stage of EPA’s endangerment finding looms on the horizon, the passing of that milestone won’t stop 100LL sales immediately. But the pressure will be real from those who would use that as an incentive to push forward on that tack.

As Bunce concludes, “The EPA cannot regulate aviation; that is the FAA’s preview. The formal endangerment finding ruling expected by the end of this year will not allow entities to close airports immediately and will not ban leaded avgas immediately. What it will do is kick off the FAA rulemaking process, which is a multiyear journey—which hopefully aligns with our EAGLE timeline of no later than the end of 2030, but sooner if a commercially viable unleaded fuel emerges. 

“The danger to the industry would be for communities to ban 100LL prematurely using the EPA ruling, which is just the start of the regulatory process, before we have the commercially viable replacement. This emphasizes the importance of EAGLE and having a methodical and transparent transition plan.”

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