N APRIL 2010, THE ENVIRONMENTAL Protection Agency released an announce- I ment that it was proposing to gather data to determine if leaded avgas is an environmental health hazard. The announcement in the form of The EPA an advanced notice of proposed rule Tetraethyl lead (TEL) is added in small making (ANPRM) has created reac- amounts to aviation gasoline (avgas) to tions that range from a willingness to boost the octane number. Avgas must have move forward in the search for the an octane number of 100 to protect today’s new lead-free avgas to alarm at the idea high-powered engines from detonation. of government mandated changes and TEL was removed from auto gas in outrage due to what some see as a mis- 1996, and although there were a few guided plan to replace one boutique fuel glitches during the transition period, with another. Regardless, the ANPRM served as a wake-up call to GA that 100LL is on the way out and the avia- tion community needs to figure out what to do next. Responders to the ANPRM ques- tioned whether the tiny amount of lead in the GA fuel supply, which ac- counts for one-10th of 1 percent of the transportation fuel used in the country each year, presents a credible threat to health. Some bemoaned that scant at- tention was being paid to the fact that supplies of ethanol-free premium auto gas — a viable and FAA-approved fuel for more than 150 piston-powered airplane types and approximately 70 percent of the airplanes plying the AVGAS skies — are rapidly shrinking due to congressional mandates to increase ethanol usage, a state of affairs that actually required more pilots to use ALTERNATIVES 100LL instead of a viable unleaded auto-gas alternative. “This industry is dealing with a The coming demise of 100LL raises massive changeover situation, and people don’t seem to realize how big more questions than answers, but there this issue is,” said Lycoming senior vice president and CEO Mike Kraft at Air- Venture 2010. “When you change the appears to be hope in the wings. fuel, you change a primary element of >>> BY STEVE ELLS this industry.” 56 FLYINGMAG.COM / FEBRUARY 2011 FEBRUARY 2011 / FLYINGMAG.COM 57 ETHANOL: C 2 H 5 OH have submitted applications for ASTM or a related aromatic, such as one of standards for their fuel. the forms of dimethylbenzene, in place Even though Glenn Passavant, of TEL to jack up the octane of high- EPA’s project manager for this issue, grade aviation alkylate base stock. The told the industry at AOPA Summit other company will grow its supply 2010 that “over the next several years of mesitylene by converting biomass we will start getting more monitoring via a proprietary catalytic process to data,” suggesting a leisurely approach produce sufficient quantities of this to the transition, key industry players aromatic hydrocarbon. don’t think we have that kind of time. General Aviation Modifications Engine manufacturers Lycoming and Inc. (GAMI) of Ada, Oklahoma, has TCM are urging adoption of the new developed a petroleum-centered plan avgas standard within the next year. for producing the new avgas: Add aro- matic compounds such as mesitylene Octane Boosters and/or one of the xylene offshoots to There are a multitude of challenges the high-quality alkylate base stock (94 in creating an unleaded alternative to octane) that’s already in production as 100LL, but chief among them is find- the base stock for today’s TEL-laced ing a replacement for the lead. 100LL. Xylene is a plastic precursor D-910 restricts the maximum amount and is plentiful. Ta-da! An avgas that of TEL in 100LL fuel to 2.0 milliliters can be put into production using exist- per gallon. Real-world 100LL airport ing production facilities and matching pump supplies almost always contain up very well with almost all D-910 less lead, so our engines can clearly get performance mandates. by without that maximum amount. Modifications must be implemented The good thing is that TEL is not at the production plants, but George the only octane enhancer we know of. Braly, chief engineer at GAMI, said The bad news? Some are more hazard- the fuel can be made with components ous than TEL. Beginning in 1992, “that are found inside the fence of any methyl butyl tertiary ether (MBTE) refinery.” Braly predicted a price of $5 was added to automobile gasoline to $6 a gallon for G100UL, the com- to raise the octane number but was pany’s replacement fuel. Braly added, lead-free auto fuel has worked well. requested that the agency determine if busy GA airports around the country transportation infrastructure and will phased out beginning in 1999 due to its “G100UL can be made at any of the Despite its octane-boosting proper- TEL in avgas constitutes a threat to pub- to quantify the amount of lead being be in high enough demand to attract groundwater-polluting characteristics. seven or eight refineries around the ties, TEL is not without its share of lic health or welfare. And to make mat- emitted during flight operations. investors and producers. Mesitylene — also known as 1,3,5- country that produce 100LL avgas.” negative side effects. In addition to ters worse for 100LL, in 2008 the EPA Take the lead out of today’s avgas American Society of Testing and trimethylbenzene — is an aromatic hy- Swift Technologies of West Lafay- toxicity issues, some piston engines are found that adverse health effects occur at and the octane number drops to 94 — Materials (ASTM) standard D-910 drocarbon that’s been proved to provide ette, Indiana, has a different plan. prone to spark plug fouling, valve stick- much lower blood-lead levels than was still high enough to protect the majority establishes 44 parameters for today’s adequate detonation protection for to- The Swift formulation is a binary ing caused by lead adhering to valve formerly understood. As a consequence of today’s engines but not all engines. leaded avgas. One of the challenges in day’s high-performance aircraft engines. (two-part) fuel consisting mostly of stems and valve guides, piston-ring the National Ambient Air Quality Stan- Adoption of a new avgas that does not creating a lead-free avgas is determining Most of the mesitylene now available is mesitylene mixed with a small amount land contamination and preignition dard (NAAQS) for lead was reduced by provide the same detonation protection how closely the new avgas formulations manufactured in China. One estimate of isopentane (2-methylbutane). The due to lead deposits on piston crowns. an order of magnitude from 1.5 to 0.15 as today’s 100LL avgas would instantly comply with these parameters and, if puts the quantity in the United States difference is that the Swift supply Both Teledyne Continental Motors micrograms per cubic meter. render most twin-engine and high- they don’t, whether or not the devia- at less than six railroad tank cars. It’s of mesitylene will be extracted from (TCM) and Lycoming have published At a public forum during AOPA performance airplanes unairworthy. tions are acceptable. Alignment with expensive on the bulk market. Yet it’s biomass through a catalytic process more than one service directive related Summit late in 2010, the EPA sug- the parameters makes it much easier for a critical component of new avgas for- developed by John Rusek, who has a to the negative effects of TEL. gested that around 50 percent of the Toward a New Avgas the airframe and engine manufacturers mulations being developed by both of doctoral degree in chemical engineer- The momentum against 100LL airborne lead in the United States can Ideally the new lead-free avgas re- and the FAA to approve the new avgas the two companies vying to produce ing and atomic physics, and Jon Zi- has been building for years. In 2006 be linked to 100LL avgas. The EPA is placement will be affordable, will fit for use in both today’s legacy airplanes tomorrow’s lead-free avgas. ulkowski, vice president of renewable a petition was filed with the EPA that conducting air sampling studies at five easily into the present production and and tomorrow’s airplanes. fuels at Swift. The production process A new ASTM specification will be New Fuels on the Horizon has been proved on a small scale. written for an unleaded fuel formula- One of the companies is forging ahead Mary Rusek, spouse and partner, tion. Both of the two companies work- with a traditional petroleum-based ap- said that one of the advantages of Swift ing on formulations for lead-free avgas proach. Its formulation uses mesitylene fuel is that it can be made from local TETRAETHYL LEAD: (CH3 CH2 )4Pb 58 FLYINGMAG.COM / FEBRUARY 2011 FEBRUARY 2011 / FLYINGMAG.COM 59 biomass such as “wood chips in the two engines is the compression ratio. oppose ethanol mandates; in fact, Con- Northwest, sorghum in the South or Doo said TCM tested the fuel to gress recently passed legislation mandat- METHYL TERTIARY BUTYL ETHER: C 5 H 12O sugar beets from Maine.” Rusek also determine how well the company’s high- ing higher levels of ethanol in auto gas. said that Swift already has signed let- powered engines performed on 94UL. There is a growing consensus that a ters of intent from five out of the six “94UL has an existing ASTM spec, 100-octane replacement fuel of some U.S. companies seeking expansion in doesn’t say there has to be zero lead — The more pressing concern for the oil companies to distribute 100SF.