With the deadline for the comment period on the Environmental Protection Agency’s advanced notice of proposed rulemaking (ANPRM) to phase out leaded avgas having just passed, many in the industry remain galvanized for possible effects of the proposed mandate.

The EPA published the ANPRM at the end of April, stating its intention to determine whether emissions from aircraft using leaded aviation gasoline (avgas) cause or contribute to air pollution, which can endanger public health. While the Industry Avgas Coalition, a group consisting of aviation associations such as NBAA, AOPA and NATA, along with petroleum industry representatives asked the agency to extend the deadline to the end of October, the EPA settled on August 27.

The 107-page ANPRM was issued in further response to a 2006 petition submitted by the environmental activist group Friends of the Earth titled “Petition for Rulemaking Seeking the Regulation of Lead Emissions from General Aviation Aircraft Under § 231 of the Clean Air Act.” Section 231 of the Clean Air Act establishes the EPA’s authority to regulate aircraft emissions of air pollution.

The most recent revision of the National Ambient Air Quality Standard, formulated in 2008, found that serious health effects could result from much lower levels of lead than previously believed. The standard did not identify a safe level of lead exposure. Under the Clean Air Act, if the EPA administrator determines lead emissions from the use of leaded avgas “cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare,” then the agency would be mandated to establish emissions standards for piston-engine aircraft in conjunction with the FAA. Establishment of such standards would include evaluating the technical feasibility of reducing or eliminating leaded aviation gasoline.

For future aircraft, this could mean a requirement that all newly manufactured general aviation piston engines run on unleaded aviation gasoline by some future date. For in-service aircraft, the EPA acknowledges greater technical and logistical hurdles. “In many cases, the implementation of this concept might depend upon efforts and actions of aircraft and engine manufacturers in identifying the necessary modifications and developing hardware as necessary,” the agency noted.

According to the General Aviation Manufacturers Association, in 2008 the ranks of U.S. piston-powered aircraft included 144,220 singles and 18,385 twins. “Given the potentially large number of affected aircraft and the potential complexities involved, a program affecting in-use aircraft engines would need careful consideration by both the EPA and FAA, and the two agencies would need to work ­together in considering any potential program affecting the in-use fleet,” the ANPRM stated. According to the document, the FAA would also be required to prescribe standards for the composition or chemical or physical properties of piston-engine fuel or fuel additives to control or eliminate aircraft lead emissions.

A ‘Persistent Pollutant’
“In the 20 years of working on this and testing of many hundreds of different variations of fuels, it has been determined that nothing does what tetraethyl lead does as well, as efficiently or as economically,” said Rob Hackman, AOPA’s vice president of regulatory affairs. “At this time there is no ‘silver bullet’ replacement for 100LL. There are some potential solutions out there that are being further researched, but to date we haven’t come up with something that we can just drop in seamlessly.” Of those solutions, two that show promise and have been flight demonstrated are offerings from General Aviation Modifications (GAMI) and Swift Enterprises. GAMI has tested its 100UL fuel in a Cirrus SR22, while Swift demonstrated its 100SF at Sun ’n’ Fun by powering a Piper Seminole. “The general aviation avgas coalition looks forward to seeing data from GAMI, Swift and any others who may have a potential solution,” said Hackman. “With that data we can examine the production, distribution, performance, emissions and economic impacts associated with any given proposed alternative.”

The EPA classifies lead as a persistent pollutant; particles of the heavy metal that are dispersed through the air as emissions will eventually settle and contaminate soil or water. Piston-engine aircraft operating on leaded avgas represent the largest source of aerial dispersal, contributing about half of the National Emission Inventory in 2005, according to the agency. Of the approximately 27 million hours flown by general aviation aircraft in the U.S. annually, piston-engine aircraft account for approximately 66 percent. Across the country, leaded avgas can be found at nearly 20,000 airport facilities, and the EPA estimates that up to 16 million people reside near facilities servicing piston-engine aircraft that are operating on leaded avgas. Recent monitoring studies indicate that lead levels in ambient air at and near airports serving piston-engine aircraft are higher than lead levels in areas not directly influenced by a lead source.

When the EPA issued the ANPRM, it requested public input on its available data, which the industry avgas coalition members described as “a key opportunity for the general aviation community to provide comment regarding this possible new environmental standard and into the development of a plan for identifying, evaluating and ultimately transitioning to an unleaded fuel.” According to the avgas coalition, industry organizations have devoted more than 20 years of research and development to identifying a viable alternative to the 100 “low lead” avgas formulation currently used by most piston-powered aircraft. These organizations “look forward to continuing their work with the EPA and FAA on establishing a realistic standard to reduce lead emissions from GA aircraft along a transition timeline that balances environmental benefit with aviation safety, technical feasibility and economic impact,” according to the coalition. 

In June, the coalition detailed its future avgas strategy and transition (Fast) plan, which it believes will help ensure the availability of 100LL until a replacement is created. The plan identifies several goals: establishing a process to develop a viable unleaded alternative to 100LL; creating incentives for the development of high-octane unleaded avgas; establishing a transition timeline that addresses aviation safety, technical feasibility and impact upon the GA and avgas industry; and minimizing potential impacts of EPA actions upon GA.

Sen. Mark Begich (D-Alaska), co-chair of the Senate GA caucus, also voiced his concerns about the proposed phase-out of 100LL before “a suitable, affordable replacement is found.” Noting his constituents had “six times more pilots and 16 times more airplanes than the rest of the country,” Begich said the premature regulation of leaded avgas would have a substantially negative impact in his state. “At this point the potential costs to Alaska associated with regulating avgas far outweigh the benefits and threaten to leave Alaska’s rural communities without a reliable means of transportation.”

In response to the growing criticism, at EAA AirVenture in  Oshkosh in July, the EPA told the coalition that it will work with the GA industry and the FAA, as it seeks a safe and viable alternative to leaded avgas. In a letter, the EPA said it “has not established or proposed any date by which lead emissions from aircraft operating on leaded avgas would need to be reduced. In fact, the EPA does not have authority to control aviation fuels,” the letter stated, in a nod to the FAA’s jurisdiction.

As the matter has only just begun its legislative journey, it may be some time before operators can expect any regulatory action, according to Hackman. “I tell folks that this is a marathon, not a sprint. It’s a little early to speculate, but I think we are looking at a number of years for this all to play out.”