What Will Fuel Our Flight Training Fleets?

Migration 2022 was held Tuesday and Wednesday this week at the Aerospace Center for Excellence’s Ramos Skylab at the Lakeland Linder International Airport (KLAL) in Florida.

The future was definitively in attendance. The U.S. representatives for Pipistrel—and its EASA-certificated Velis Electro two-seat all-electric trainer—from Right Rudder Aviation participated. And leaders from VTOL startup Joby Aviation’s newly launched flight training organization, Stockton Ballantyne and Cody Cleverly, joined the conversation. 

Pete Bunce, president and CEO of the General Aviation Manufacturers Association (GAMA), and Walter Desrosier, GAMA’s director of engineering and maintenance, laid out the problem statement and the current position the general aviation industry is in during a keynote session Wednesday. 

Redbird’s vice president of sales and marketing, Josh Harnagel, related that, as they approached the event, the Redbird team considered making GAMA’s presentation a breakout session, but the inflection point that the GA industry has come to demanded that all 200 flight training leaders at the conference have a chance to hear the message.

“The most efficient way right now of getting into the air is blowing up dinosaurs,” Bunce said. But the fact is that development toward electric aircraft is not just in the urban air mobility (UAM) space, but also driving up to regional and commercial aviation. He noted how Eviation’s all-electric Alice—which is expected to make its first flight soon—is patterned after a business jet, but with unconventional powerplants. 

Traditional aviation OEMs such as Bell are getting into the game too. And Embraer’s Eve consortium will go public in the next few weeks, with an end-to-end UAM solution proposed, all the way through to a new ATC infrastructure plan to sell into the developing world.

Additionally, there are several projects—including ZeroAvia’s—using gaseous hydrogen to power aircraft—and from a potential energy standpoint these hold promise. But as Bunce pointed out, we need the hydrogen infrastructure specific to aviation in order to make those test aircraft operational and economical in the real world.

“[In aviation] we have the tougher challenge,” as far as needing the high potential energy stored in petroleum-based fuels, “and we should be the last ones able to use it—but that’s not the way the world is going,” Bunce said.

The industry already has developed several pathways to producing sustainable aviation fuel (SAF) from various sources, with the ASTM involved in this process using as many as 7 authorized roadmaps.

Right now, we can blend only 50 percent sustainable fuel stock into a jet-A formulation, because of the need to add back in aromatics to augment the base feedstock—in aircraft powerplants, it comes down to critical factors such as protecting seals and other components within the engine and system.

There isn’t enough feedstock in aggregate to serve the industry right now either, as Bunce noted.

“We’re trying to break out that piece of the Build Back Better bill to keep Biden’s challenge alive,” he said.  He noted the commitment made by signatories to the National Business Aviation Association (NBAA) last fall to drive to zero emissions by 2050. “The only way to get there is with SAF—new aircraft design won’t get there,” he said.

But he’s excited about the current state of affairs in GA and for aviation overall. “I look at this time in the industry—this has got to be what the dawn of the jet age was like.”

GAMA’s Walter Desrosier put it bluntly as he continued the presentation: the continuity of the avgas supply is key to the stability of the GA industry. The fuel used by most of the piston fleet, 100LL, contains a specific compound—tetraethyl lead or TEL—to deliver lead’s protective properties to the fuel.

One facility in the world manufactures TEL, and that’s Innospec, Inc., in the U.K. He noted that Brexit helped continue the production of TEL for a while longer because Innospec’s production facility is no longer operating under EU oversight, but the pressure remains intact.

Much of the training fleet—using relatively low-compression engines—can use the UL91 and UL94 unleaded fuels currently entering the market in the U.S. Overall, 67 percent of the GA fleet can use these fuels, and they are essentially drop-in—there’s paperwork and placarding involved, but little else.

But the remaining 33 percent of high-performance aircraft in the fleet require 100LL—and those aircraft will keep flying as long as they’re able. With the average age of the GA fleet at 47 years, pilots hang onto their airplanes, so it’s not like the automotive industry where lead-burning cars could be phased out and converted over a roughly 10-year period. “That transition option is not available to us,” said Desrosier.

Consumption of avgas skews the breakdown even more: 70 percent of avgas consumed needs to be 100LL. “We haven’t found a silver bullet,” that would take us to a drop-in solution, said Desrosier. A “non-drop-in” solution would require at the very least an operational impact, changes to fuel production and distribution, and require FAA certification and approval for each airframe and powerplant combination.

In California, the answer has already been forced upon a handful of flight training organizations, including Trade Winds Aviation at Reid-Hillview (KRHV) and San Martin (E16) airports in Santa Clara County. 

But Bunce also mentioned a movement underway at the Santa Monica Airport (KSMO) in the Los Angeles Basin to go the same route as Santa Clara toward a total ban on the sale of 100LL on the field.

There are future fleet solutions in electric aircraft—but they admittedly have limited utility. Pipistrel’s Velis Electro has the endurance for traffic pattern work, but not much else at the moment. FLYING will cover the electric aircraft question in more detail in a follow-on piece to come.

The recommendation for now? Research and proactively source unleaded avgas for those aircraft in the training fleet that can use it now—before the requirement for using it is forced upon the flight school operator.