It had to happen. Ever since leaded automotive fuel was phased out in the 1970s, there’s been talk about getting the lead out of avgas as well. More recently, we’ve been through several efforts to define a replacement for 100-octane leaded fuel, but now one California county is attempting to force the issue by banning the sale of leaded fuel at the Reid-Hillview airport. (As of mid-January, flight planning resources show 100LL as not available, though 94UL is.) The county’s move received a rapid response from industry groups, including AOPA, which described the move as “reckless” and “politically motivated.” The county’s actions are, in my view, consistent with its larger plan to force the closure of Reid-Hillview. The value of land has skyrocketed in this part of California since Amelia Reid plied her craft against the golden hills of Santa Clara county.
For the moment, the skirmish is limited to KRHV, but we’d be fools to think other municipalities aren’t watching what happens, especially those whose airports were built long before the surrounding communities became a thing and now see this “egregious” use of land as a waste of potential tax revenue. Airports have enough challenges from land use and noise as it is; we don’t need a public panic about “deadly” leaded fuel.
No Easy Solutions
But here’s the deal: lead is a monstrously effective octane booster. Other concoctions used to raise octane to meet the current spec tend to have some negative characteristics. You could have materials incompatibility, problems with vapor pressure or other factors that make 100LL alternatives unsuitable. At the moment, two fuels stand out as viable replacements: GAMI’s and Swift’s. More on that in a second.
It’s easy to consider 94UL, which is essentially our current 100LL fuel without the tetraethyl lead, a viable stand-in. But it’s not, not quite. Those of you well-aged pilots will remember when FBOs had multiple tanks and various-octane fuels to purchase. Where once there was a choice of 80/87 (that’s the lean versus rich rating) or 100/130, the industry gradually switched over to a single solution, the so-called “low lead” 100/130, which we know as 100LL. By this time, many FBOs and airports chose to refine their tankage—in some cases, they were often forced to by local laws on the storage and handling of gasoline—and nearly all consolidated to one system for one fuel. Ask your airport manager if it makes sense to install a second set of tanks and how long it’ll take to recoup the investment. You’ll get a blank stare.
Then, as now, there was a great disparity in aircraft needs. According to AOPA’s own numbers, some 75% of the current fleet can use a fuel less resistant to detonation than 100LL. In fact, these lower-compression, non-turbocharged engines would be much happier without the lead at all, and in places where the 94UL alternative is available, it’s a good choice for these engines.
But here’s the rub: The 25% of the fleet that needs, absolutely needs, a 100-octane fuel consumes some 75% of the volume each year. We’re talking big turbocharged piston engines in commuter and freight applications. The number of RVs far outstrips the fleet of 400-series Cessna twins, for example, but those twins fly every day, all day at nearly 40 gph in cruise. What those Cessnas suck down in a day takes your average RV a quarter of a year to burn.
Where We Are Now
GAMI’s G100UL fuel was approved as of last summer and can be used with an STC for a limited number of Lycoming engines and Cessna airframes. I’ve seen the data created by the extensive detonation testing by GAMI, and it’s impressive. If anything, the turbo-normalized Continental 550 engines were happier on G100UL than a standard-spec 100LL, and they represent something of a worst-case scenario for detonation. Our engines, even your fire-breathing, 10.0:1 hot rod, should be free of detonation with the G100UL. (Full disclosure, I was provided a full tank of early G100UL to test in my Sportsman more than a decade ago. It worked splendidly, though 50 gallons is hardly a viable data set of long-term effects.) Swift has developed 94UL, of course, and continues work on a “drop-in” replacement. Shell is also hard at work on a replacement, but there appear to be some material-compatibility issues yet to be resolved.
And there’s your problem. There is no easy solution to finding one fuel that works on everything from Ercoupes to Piper Navajos. Worse, the FAA’s Piston Aviation Fuels Initiative (PAFI) that was coordinating development of an unleaded alternative is, by decree, unable to discuss progress. So we live in the dark.
The events at Reid-Hillview should remind us that the clock is really, no-joke ticking on 100LL. If the EPA finally issues a Finding of Endangerment related to leaded fuels, the alarm will go off, and we’ll have to face the consequences of a suddenly accelerated timeline. That’s no way to wake up.
You may notice a few tweaks to our content over the next few months. For starters, Dave Prizio, who has penned our Maintenance Matters section for a very long time, has asked for a break from the monthly grind—and who can blame him? So we’ll be giving that column a rest for now, though we’ll continue to cover engine- and airframe-maintenance topics while he’s resting.
In the coming months, you’ll also see more of Vic Syracuse; in addition to his “Unairworthy” and “Checkpoints: Diagnosis” contributions, he’ll be chiming in with other commentary and an ongoing build series. (I’ll let the subject of that series be a surprise.) Also, you’ll see more of Gabriel DeVault, whose electric Xenos motorglider graced our cover some months ago; his perspective on working with electric propulsion is an important part of that category’s progress. It’s one thing to speak conceptually about electric aircraft, as we have done for more than a decade, but I think his hands-on experience is hugely valuable.
David Howe commented on Bob Hadley’s “Toe Bar” article in the February issue. “You made a photo caption comment about using only ‘raw’ plain steel fasteners for welding so as not to gas off toxic fumes. I’m sure you know this and just elected not to include it, but pool ‘service’ strength muriatic acid removes most commercially applied protective coatings, including cadmium plating.
“This feature simplifies the selection process to almost whatever is in your inventory. As a longtime TIG welder, I have a gallon of it on hand and probably use it a couple of times a week to get materials ready to weld. Another advantage of the ‘raw’ surface condition is the absence of contamination potential. TIG welds, as you are well aware of, hate contamination.”