The 100UL Future

That's especially surprising if you recall the crisis atmosphere of 2010, as the Environmental protection Agency (EPA) moved to issue rules for regulating leaded avgas, pilots worried about where their next tank of high-octane fuel would come from, and the General Aviation (GA) industry was ready to scale back on R&D after two decades of failure to find a "drop in" replacement for 100LL---that is, a replacement that required no modification of aircraft engines or the fuel distribution infrastructure.

"There was some panic in the industry, and a kind of marketplace paralysis," says Doug Macnair, vice president of Government Relations at the Experimental Aircraft Association (EAA), which has long been involved in the avgas issue. "People did not overhaul engines, they were not purchasing aircraft, and they were prematurely selling, because of fear."

That year at AirVenture Oshkosh, members of the General Aviation Avgas Coalition, which includes GA's leading membership organizations, asked the Federal Aviation Administration (FAA) to head a public-private development partnership aimed at creating a 100LL alternative.

"No one wanted to take on the leadership role," says Peter White, manager of the Office of the Alternative Fuel Programs Staff, command center for the FAA's UL development activities. That's understandable.

About 34% of the U.S. GA fleet of more than 200,000 piston- engine aircraft require high-octane fuel to perform properly, and lead is the best octane booster known. [See Sidebar: 100 LL.] But finding a replacement for lead is only part of the challenge. The chemistry of the fuels is completely different, and characteristics including distillation curve, vapor pressure, water separation and freeze points, energy density/weight, corrosiveness, stability, toxicity and conductivity are critical. The ingredients must also be compatible with the vast range of materials across the production and distribution chain, and in your airplane's engine and fuel system.

White calls the undertaking "one of the most complex and largest certification efforts that has ever been done in aviation." The technological hurdles, certification costs, regulatory hoops and liability concerns, not to mention gaining marketplace acceptance as 100LL's true replacement, appeared too daunting for the private sector. (Or maybe just not profitable enough, given the relatively small market.) But the FAA had never taken on a program like this, either.

"We were asking the FAA to be the applicant, data producer, and authorizer---to play every role in the transition, something they'd never done before," says Macnair. "And, through lengthy discussions and negotiations, to their credit, they recognized that there was no other way forward to a full fleet solution---at least, not in our lifetime."

It's supposed to power today's and tomorrow's high-performance piston aircraft, tomorrow. But who knew the stalled search for a 100 octane unleaded (100UL) avgas would propel a model of industry-government collaboration---and a five-year program that's on track to authorize at least one 100LL (low lead) replacement fuel for the U.S. piston fleet before the end of 2018?

That's especially surprising if you recall the crisis atmosphere of 2010, as the Environmental protection Agency (EPA) moved to issue rules for regulating leaded avgas, pilots worried about where their next tank of high-octane fuel would come from, and the General Aviation (GA) industry was ready to scale back on R&D after two decades of failure to find a "drop in" replacement for 100LL---that is, a replacement that required no modification of aircraft engines or the fuel distribution infrastructure.

"There was some panic in the industry, and a kind of marketplace paralysis," says Doug Macnair, vice president of Government Relations at the Experimental Aircraft Association (EAA), which has long been involved in the avgas issue. "People did not overhaul engines, they were not purchasing aircraft, and they were prematurely selling, because of fear."

That year at AirVenture Oshkosh, members of the General Aviation Avgas Coalition, which includes GA's leading membership organizations, asked the Federal Aviation Administration (FAA) to head a public-private development partnership aimed at creating a 100LL alternative.

"No one wanted to take on the leadership role," says Peter White, manager of the Office of the Alternative Fuel Programs Staff, command center for the FAA's UL development activities. That's understandable.

About 34% of the U.S. GA fleet of more than 200,000 piston- engine aircraft require high-octane fuel to perform properly, and lead is the best octane booster known. [See Sidebar: 100 LL.] But finding a replacement for lead is only part of the challenge. The chemistry of the fuels is completely different, and characteristics including distillation curve, vapor pressure, water separation and freeze points, energy density/weight, corrosiveness, stability, toxicity and conductivity are critical. The ingredients must also be compatible with the vast range of materials across the production and distribution chain, and in your airplane's engine and fuel system.

White calls the undertaking "one of the most complex and largest certification efforts that has ever been done in aviation." The technological hurdles, certification costs, regulatory hoops and liability concerns, not to mention gaining marketplace acceptance as 100LL's true replacement, appeared too daunting for the private sector. (Or maybe just not profitable enough, given the relatively small market.) But the FAA had never taken on a program like this, either.

"We were asking the FAA to be the applicant, data producer, and authorizer---to play every role in the transition, something they'd never done before," says Macnair. "And, through lengthy discussions and negotiations, to their credit, they recognized that there was no other way forward to a full fleet solution---at least, not in our lifetime."

Going From Low To No
In 2011, the FAA established the Unleaded Avgas Transition Aviation Rulemaking Committee (UAT ARC), comprised of FAA, EPA, the GA alphabet groups and industry stakeholders, to draft the project blueprint. Early the next year, UAT ARC laid out its roadmap, a short list of recommendations whose centerpiece was the Piston Aviation Fuels Initiative (PAFI). The five-year program would test candidate high octane unleaded fuels created by private developers ("offerors" in PAFI parlance)---identify one or more suitable as 100LL replacements requiring little or no modification to existing aircraft systems or fuel delivery and storage infrastructure---and bestow FAA fleet-wide authorizations and set the American Society for Testing and Materials (ASTM) specifications needed to produce and bring the fuel(s) to market.

In Washington, the GA lobby rallied Congressional support. The FAA Modernization and Reform Act of 2012 mandated the agency create a collaborative R&D program to qualify an unleaded fuel for GA's piston engine fleet. That summer the FAA created the Fuels Program Office (which includes the Alternative Fuels Programs Staff), to serve as the central certification office, and then formed the PAFI Steering Group (PSG) to oversee the program. A Technical Advisory Committee (TAC) was established to develop the test program, and a Technical Evaluation Committee (TEC) to analyze the results and select the fuel(s) for certification. The President's budget request shows full funding for the program, at about $6 million per year, through 2018.

"I'm confident this will result in a fuel that will be around for a very long time, and will maintain the health and safety of general aviation," says David Oord, Aircraft Owner & Pilots Association's (AOPA's) vice president, Regulatory Affairs, echoing the comments of many program participants.

Meanwhile, the industry has pledged to contribute resources, material, services and time to the effort. Continental Motors, Lycoming, Textron Aviation, and Cirrus and Piper Aircraft are among the engine and aircraft manufacturers providing hardware and expertise to PAFI.

"We have seen entities within the FAA and user groups and OEMs (Original Equipment Manufacturers) come together and work collaboratively to meet the needs of flying public, so I see that as a very positive sign," says Douglas May, vice president of Piston Aircraft at Textron.

(Though Textron owns Lycoming, and China's AVIC, parent of Cirrus Aircraft, owns Continental Motors, both engine OEMs are run independently from sister companies, and neither Textron/Lycoming nor Cirrus/Continental has leveraged its shared ownership pursuant to 100UL research, the companies told P&P.)

A Two Phase Approach
PAFI is a two-phase winnowing process. Phase 1, the preliminary testing of candidate fuels, is now concluding. By the July 2014 submission deadline, 17 fuels from six offerors had been provided for consideration, and that September, after analysis by TEC, four of those fuels from three offerors (Total, Shell Oil Co., and two from Swift Fuels) were down selected for the Phase 1 evaluation tests.

Conducted since March 2015 at the FAA's William J. Hughes Technical Center in Atlantic City, New Jersey, Perdue University and contract facilities, Phase 1 tests have examined fuel properties including detonation and emissions, carburetor icing tendencies, cold storage, hot surface ignition, and low temperature fuel flow.

The range of industry participants in PAFI ensures all facets of the production and distribution chain are considered. "We try to provide for Phase 1 testing our smorgasbord of parts, seals and diaphragm material, and metal mixes that we feel truly gives us a good first look at how these fuels might attack our parts," says Mark Voss, Certification and Continued Airworthiness Engineer at Continental Motors.

The National Air Transportation Association (NATA), which represents FBOs, charter and other airport service providers, monitors "the unique handling characteristics of any future unleaded aviation gasoline, as well as any possible changes required for storage and delivery systems," says Megan Eisenstein, the group's senior manager, Regulatory Affairs.

Offerors have been receiving Phase 1 test results as they become available. Swift Fuels CEO Chris D'Acosta says his company's two test fuels have been rated at "102 octane or higher" and "showed strong anti-detonation results." Shell and Total haven't made public any test results. (Shell declined to speak to P&P on this topic.)

With Phase 1 testing complete, Lycoming and Continental have received their donated fuel system equipment back and completed teardowns (without knowing what fuel was run through each system), which will help anticipate each fuel's impact on an engine, says Michael Kraft, Lycoming's senior vice president and General Manager. The companies will issue condition reports to TEC, and following their analysis, the committee will down select two or three of the Phase 1 fuels to proceed to Phase 2. It's expected at least one of these will subsequently be authorized for use in the piston fleet after Phase 2 concludes in 2018.

Though proprietary formulations, no provider will have a monopoly on the fuel supply. As part of their submissions, offerors presented a business model for fuel production and distribution.

"Every one of candidates has said their plan and approach is to have an industry consensus standard by ASTM, just like today," says Walter Desrosier, vice president at the General Aviation Manufacturers Association (GAMA), another lead organization in the alternative fuel quest. "There will be some proprietary elements, but the plan is to allow them to be mass produced."

Interestingly, projected price is not one of the judging criteria, but program participants expect the most easily produced and distributed fuels to have the lowest cost. "As a consumer group, my interest is to have it be competitive with 100LL," says Macnair. "There's no pie in the sky belief it will be cheaper, but you can't have some magnitude leap in the price of avgas and expect it to work."

Independent Efforts
PAFI itself has no monopoly on developing a 100UL standard. The FAA also supports efforts to find an unleaded replacement outside of PAFI's confines. Fuel developers or engine OEMs, for example, may apply for Supplemental Type Certificates (STCs) permitting a fuel's use in given engine/airframe combinations. Offerors whose fuels wash out of the PAFI program are welcome to pursue an STC route to approval, though the fleet-wide authorization the FAA intends to bestow is a huge benefit in reducing development costs and achieving marketplace acceptance.

Gami, manufacturer of engine monitoring instrumentation, has been engaged in an effort to develop a 100 octane unleaded product for some 15 years at its in-house testing facility, and is pursuing an STC for its G100UL fuel.

"We felt we were better off and could be faster and more in control, than by having the FAA control [the process] for us," says Gami president Tim Roehl of the STC route to approval. Gami has a Project Specific Certification Plan (PSCP) with the FAA, which the company expects to result in two STCs: One will cover approved engines via an Approved Model List (AML), the second an STC of approved airframes. Roehl says the first group engine/airframe combinations approved will include Cessna 172s and similar engined aircraft models, a second group will include the Cirrus SR22 and other high performance aircraft, and a third and final group will cover the remainder of the piston fleet, "such that at completion, we will have essentially a fleet wide approval for every airplane and engine combination."

Roehl says Gami will wait until it has STCs in hand before trying to interest the market in the unleaded fuel.

Phase 2 And Beyond
Selection of Phase 2 fuels is anticipated in January or February, with initial deliveries of the selected formulations arriving by July 30th of this year. Phase 2 testing will be more rigorous and comprehensive, and involve a "broad range of aircraft and engines," says White. A Cirrus SR22 equipped with a calibrated Continental TSIO 550K will be among the combos.

Additionally, PAFI wants seven engines each from Continental and Lycoming for Phase 2 testing, and as we went to press the companies were formulating proposals. "We opted to participate in Phase 1 entirely at our expense," says Voss at Continental. "Phase 2 is more than an order of magnitude more expensive, so it becomes more critical to look strategically at how we want to support that."

Data generated in Phase 2 will be used to determine the ASTM production specification for producing the fuel. The closer the fuel conforms to current specs for 100LL, the easier and simpler the transition. Ideally, it would be the long awaited "drop-in" (or "transparent" in current PAFI terms) replacement avgas for at least a significant portion of the fleet.

Fleet-wide authorization to use the new fuel(s) could be as simple as publishing a list of approved airframe-engine combinations in the Federal Register. Legal scholars within and outside the FAA believe the agency has the requisite regulatory power, but plans call for including language in the forthcoming FAA Reauthorization legislation that makes such authority explicit.

Aircraft will have to be placarded appropriately, for example at the fuel fills, and logbook entries and Pilot's Operating Handbook (POH) changes will likely be required, White says, though it's anticipated the process will be "pretty streamlined."

Once the fuels have been authorized, aircraft are in compliance, and production standards set, "the real question is, how will the market react?," says GAMA's Desrosier.

Adds White, "We'll put two fuels in market, and they will compete. I think most people believe it will be a one fuel market in the future, [but] that remains to be seen."

Also unknown: How much of the fleet won't be covered, and the modifications they might require to use the new fuel. "In real life, there may be such and such a model number [engine] that needs certain part number hoses removed and replaced, a fuel tank issue, or a fuel flow meter issue in another," says Voss, while expressing confidence in the project's ability to handle such problems.

Meanwhile, PAFI has chartered a transition subgroup to offer guidance on setting and managing milestones for the changeover.

Questions aside, "The real message," says Textron's May, "is customers should be assured as an industry we'll be providing support to them when they start to operate these fuels."

Operators of high-compression engines are unlikely to have a choice, as the EPA, which has been waiting for the PAFI process to take its course, moves forward on leaded avgas at the program's conclusion.

"We fully expect EPA will issue an endangerment finding [on 100LL], which would then trigger automatic regulatory requirements under the Clean Air law to regulate, though not necessarily ban, [leaded] avgas," says Desrosier. Trying to comply with those standards will likely mean the end of 100LL production in 2019 or thereafter.

There's good, as well as hopeful news in all this. Looking ahead, environmental benefits aside, unleaded fuels promise improved engine maintainability and service life, once corrosive lead oxide, a byproduct of 100LL combustion, is no longer a concern.

"The immediate impact of unleaded fuel, we're going to be able to change maintenance documentation, which could potentially change the service schedule," says Lycoming's Kraft. "Lubricant providers will no longer need to deal with lead oxide contamination, and then we'll be able to change the design of engines to take advantage of new fuel lubricant systems."

So if you're flying a high-compression engine and high-performance aircraft, no need for panic or paralysis. Program participants say 100UL is coming, and failure is not an option.

"We don't have the answers now, but the program is designed to find them," says Macnair. "We are so committed to this; this is the blood of aviation."

Adds AOPA's Oord, "We essentially only have one chance to get this right."

Leaded aviation gasoline (avgas) was developed in the 1940s as a means of suppressing "knock," or detonation in supercharged engines used in military aircraft. Detonation is the premature ignition of the fuel-air mixture in the engine's cylinders due to compression; normally, the ignition is triggered by the cylinder's spark plug. Sustained detonation can have catastrophic affects on an engine, and many engines that power general aviation aircraft require 100LL (low lead) avgas for the same reason. Tetra-ethyl lead (TEL) is the ingredient that gives this avgas its lead, and consequently its high-octane rating. But lead is also a known neurotoxin shown to interfere with children's brain development, among other health consequences. Though levels of TEL in avgas have been reduced 50 percent since the 1970s, 100LL is now the only transportation fuel in the U.S. that contains lead.

The Environmental Protection Agency (EPA) is currently evaluating emissions from engines that use leaded fuel, and if the agency determines they endanger public health, it will impose emission standards. Though the regulations might not ban leaded fuels outright, many experts believe the rules would spell the end of 100LL production.

Fortunately, the EPA is coordinating its rule-making process with the Piston Aviation Fuel Initiative (PAFI), to provide sufficient time to identify an alternative to leaded fuel. It's expected the EPA will propose regulations on leaded emissions through a Notice of Proposed Rule Making (NPRM) in 2017, and a final rule is anticipated in 2018, as the PAFI program concludes.

No link between lead from avgas and environmental exposure has yet been established, nor is there evidence that emissions from piston engine aircraft cause violations of the National Ambient Air Quality Standards. EPA has acknowledged its database on ambient lead levels at airports is "severely limited," containing samples from only a few airports, and no analysis of background lead levels.

Sign up for our free newsletter to receive aircraft news, product information, pilot talk and more.