Unleaded Avgas: All On The Same Page (Not)

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There’s all kinds of shaking going on in the unleaded avgas sphere, as evidenced by revelations at Oshkosh this year. Those of us who expect the progress of science and commerce to be orderly and stately might be dismayed by the apparent confusion, indeterminacy, contradiction and flawed human behavior in the quest for a lead-free world.

Students of the history of both discovery and enterprise will see the repeat of that history, with all its wart-bespeckled lows and heady triumphs. All this to facilitate a future 50-gallon avgas fill-up.

There are four players now pursuing unleaded avgas certification: Shell and Swift, who had been selected by and participating in the now-stalled PAFI (Piston Aviation Fuels Initiative); GAMI, who has been working in this space for almost two decades; and a Phillips Petroleum/Afton Chemical consortium that announced at Oshkosh their intent to follow the GAMI path to an STC'd fuel. 

The FAA in May announced that they had encountered issues requiring mitigations for both the Shell and Swift fuels, implying that neither fuel could meet the needs of the fleet. Lacking a plan to address these mitigations, and being short of funding to complete lab and flight testing that was as much as half done, the FAA suspended further testing. It also slipped the completion date a year to 2019 and said it needed more money.

The FAA's interpretation of its legal authority is that it cannot approve a fuel as a fleet-wide replacement without special authority from Congress. Not all observers agree with that characterization, but it is conservative. Participants in the unleaded certification effort point with pride to the specific language in the FAA reauthorization legislation that confers such authority upon the FAA.

However, the reauthorization bill has only passed one chamber thus far and the president hasn't signed it. So that technical detail remains along with question: Can we do this at all? Perhaps we will be well served by the STC applicants after all. History lesson: Phillips' XC 20w50 oil was originally approved on an STC, because there was no relevant milspec for multi-viscosity at the time it appeared. So there is precedent.

One issue that PAFI participants have shared off the record is that non-linearities have been observed in comingling the two fuels with each other, and with 100LL, in various ratios. It's surprising that this surprises the FAA; gasoline blending is inherently non-linear. The ASTM's multi-industry Coordinating Research Council (CRC) that had been researching unleaded avgas alternatives since 1991 made a number of observations of these characteristics.

Certainly it's an issue. Although CRC never delivered final recommended fuels, they did make scientifically valid suggestions on how these comingling issues could be addressed. It seems the FAA folks weren't paying attention, or have forgotten what they'd heard.

Those affected by PAFI's decision to pause fall into at least two schools. Those with a background in government contracting point out that given the competitive nature of the fuel selection, the FAA would put the entire process at legal risk if they change the rules as they go along to address this current concern. Thus the pause, in their view, is essential to protect the integrity of the program from legal challenge. Those who were eliminated in earlier rounds could legitimately complain they were unfairly treated if certain contestants were given another bite of the apple without extending the same opportunity to others.

The fuel proponents, however, are less concerned about the FAA's potential legal troubles; they feel they're being placed at a competitive and cost disadvantage by delaying the testing. Once begun, the testing should be completed as outlined, they feel, to be fair to the two contenders chosen by the process. Otherwise, they're being burdened with a cost of delay that they didn't sign up for at the beginning. The particulars that emerged at AirVenture this year show how chaotic the PAFI process has been, at least from the outside looking in.

Shell gave two sessions by Tim Shea, director of Aviation R&D, on Monday and Wednesday. The presentations were oddly different. The first session, co-presented with Continental's Tim Kenney, was largely glad-handing, with the message being that Shell is good, unleaded avgas will be awesome. See you next year. Audience members asked Shea to comment on the PAFI pause. Shea deflected, inviting Oshkosh attendees to ask the FAA at the FAA's PAFI presentation. When the audience explained that the FAA had not scheduled a PAFI presentation, Shea seemed genuinely stunned, noting that he had expected the FAA to be presenting.

The second session, two days later, with Lycoming's Michael Kraft, was more in depth and did address PAFI's pause. Spirited disagreement exists between Lycoming, which believes the pause is essential due to federal regulations and essential to eventual success, and Shell, which wants the program to continue apace even with the problems identified.

Shea seemed to let slip that Shell's formulation relies on heavy alcohols instead of an -OH group with 1, 2 or 3 carbons, substituting perhaps a handful of carbons, thus making a less hygroscopic/water-loving additive. That would be more suitable for inclusion in avgas. Kraft verbally chided Shea for nominally violating the PAFI non-disclosure agreement in discussing this formulation detail, but his objection focused the attention of all attendees on the apparent gaffe.

Shell's Shea cast shade at GAMI without naming them. Shea claimed the GAMI STC process is less open and transparent than the PAFI process, implying that this was unfair to the industry. But observers noted that the PAFI process has been inscrutable to outsiders. Perhaps PAFI does a better job of sharing with participants within industry, but not with the aviation press, or with pilots and aircraft owners—the actual customers for the fuel.

Shea waxed slightly dramatic, opining that no one knows what's in the proposed STC'd fuels, what tests the FAA might or might not make the STC applicants perform, and whether or not a specification for the fuel would eventually exist. But the same is true regarding formulation and testing for the PAFI fuels, including Shell's. When the process completes, it will be apparent whether a specification exists or not. Of course, if anyone plans to actually sell any of their fuel, a specification will be essential.

Shea also took an odd tack on the driving force for the entire unleaded avgas effort, implying that since the EPA has abandoned a lead endangerment finding, a decision made shortly after the Trump administration began exerting sway at the EPA, why should industry do anything at all? The majors are perfectly happy selling a high-margin fuel that is protected by competition from upstarts by the large environmental liability of lead blending.

The conceit is that the majors already bear the lead blending burden, since using TEL in mogas began in the 1930s. But any new entrant would be inhibited from entry into avgas blending by incurring that liability. These aren't the sort of musings that corporate public relations departments like to hear their managers articulating in public. Shea seemed to ignore the lawsuits by environmental group seeking to force the EPA's hand on a lead ban. FOE (Friends of the Earth) and NRDC (National Resources Defense Council) have current focuses on the lead issue, and others could take up the banner.

And of course, administrations do change, and even a given administration can rethink its policy issues. So even if the EPA doesn't issue a lead endangerment finding in the next year or two, it's far from a dead issue. And don't forget, if the sole remaining western lead plant, Octel's near Liverpool England, burns down tonight (bad news for the downwind neighbors), it seems unlikely that anyone will be rushing in to reinvest in this end-of-life-cycle technology.

Moreover, an unleaded solution will be good to have. Lycoming's Kraft pointed out that unleaded fuel will offer many other benefits to aircraft operators: longer oil change intervals, availability of superior lubricants currently eschewed due to their inability to solubilize lead salts, and advanced engine control systems relying on lambda sensors that would today be slowly destroyed by lead salts in the tailpipe. 

Phillips Petroleum and Afton Chemical introduced their MMT (methyl manganese) formulation. They forecast it will be certified via STC by 2022. The speakers started out being cagey about the formulation of their fuel, "similar to existing avgas." The caginess was odd, since Phillips' pre-printed handout said that the fuel was identical to current avgas, except using MMT instead of lead as the octane enhancer.

The Phillips speaker finally conceded what the handout declared. Audience members asked about MMT spark plug deposits. EPA has reported that General Motors found that plugs could become contaminated in as few as 16,000 miles.

These concerns are "not valid," Afton's representative claimed, but he advised that Afton was reformulating the manganese scavenger anyway, to solve this non-problem. That's an odd business decision, in my view. Canadians will have to inform us on the spark plug glazing issues much touted in the technical press when MMT was used in mogas up north. This made their sparkplugs throwaway items, not readily cleanable.

When asked about this, the Afton representative replied that he spoke with authority, because he is a Canadian. But perhaps the unneeded and unnecessary manganese scavenger reformulation will address this issue. 2022 is a long way away, and of course that's a date from the heady early days of this effort. Still, it’s good to have an avgas heavyweight like Conoco-Phillips adding its weight to the fray. But a lot remains to be demonstrated in the engine durability testing required for certification of their proposed formulation, STC or not.

GAMI did not present at AirVenture, but the company is continuing toward STC approval certification. GAMI hasn’t revealed the exact formulation, but has confirmed that it’s based on aviation alkylate with an aromatic hydrocarbon additive package for octane enhancement. GAMI has been assembling all the pieces and seeking FAA approval for every step of their science, supply chain, blending and distribution, including launch customers to gather data to support an ASTM specification application. The FAA has implored GAMI to enter the PAFI process and GAMI has firmly demurred.

Assuming GAMI is permitted to complete their project within the scope of their FAA-approved certification plan, there could be many airplanes operated daily on GAMI 100UL by this time next year by a couple of launch customers, with broader approvals and distribution in the next two years. It may then live or die in the market, depending on its merits. 

Swift’s CEO Chris D’Acosta held forth on Swift 94 and 100, declining to discuss PAFI results. While Shea dissed GAMI, D’Acosta went after Phillips/Afton by passing around vials of a purported alkylate manganese mix that looked like sewage samples. Oddly, this criticism came shortly after he made a remark about not denigrating his competitors.

D’Acosta exhorted the crowd, "Would you put this stuff in your airplane?" Of course, we couldn't analyze Swift's fuel samples to see how they were compounded, so no technical detail is forthcoming. The refining industry did blend with MMT for years without flocculation—fine particles in the solution clumping together—being a serious concern, so this strikes me as more obfuscation than technical critique.

Both Shell and Swift might be better served by observing D'Acosta's words and favoring their audiences with details about their own products rather than casting doubt on the other guys'. Taken together and considering PAFI’s unimpressive results thus far, the road to unleaded avgas looks bumpier than ever.


Paul Millner is a retired refinery executive with expertise in avgas production. He edits the Cardinal Flyers Online newsletter.