Increasing global environmental issues and dwindling global market demand for gasoline containing lead have raised concerns regarding the continued use of avgas (100LL) by general aviation (GA) aircraft.
Congress enacted the Clean Air Act of 1970 and shortly after created the Environmental Protection Agency (EPA). In 1978 the EPA established a National Ambient Air Quality Standard for lead. Thirty-five years ago, cars and trucks were the major contributors of lead emissions to the air. In the 1970s, EPA set national regulations to gradually reduce the lead content in gasoline. By 1996, EPA promulgated regulations that banned the use of leaded gasoline in highway vehicles. As a result, emissions of lead from the transportation sector have dramatically declined (96 percent between 1980 and 2005). The addition of lead to fuel used in piston-engine powered aircraft was not banned in this action, and the use of leaded avgas is now the largest source category of lead emissions.
Piston engine aircraft include a diverse set of aircraft types and engine models and are used in a wide variety of applications. Lead is added to fuel for piston engine aircraft in the form of tetraethyl lead (TEL). This lead additive helps boost fuel octane, prevents knock, and prevents valve seat recession and subsequent loss of compression for engines without hardened valves. There are two main types of leaded avgas: 100 Octane, which can contain up to 4.24 grams of lead per gallon; and 100 Octane Low Lead (100 LL), which can contain up to 2.12 grams of lead per gallon. The use of 100 octane avgas continued in piston-engine aircraft until the early 1970s when 100LL became the dominant leaded fuel in use. Currently, 100LL is the most commonly available and most commonly used type of avgas. Very little 100 Octane is supplied in the U.S.
While past airport air quality studies show that the lead levels around most airports are under the limit set by the NAAQs, changes to the NAAQs standard highlight the important of industry’s research into a suitable replacement unleaded avgas.
Three-fourths of the U.S. fleet—167,000 of the 220,000 aircraft—are piston-powered aircraft certified to fly on leaded fuel. Lead boosts the octane of the fuel used in piston-powered aircraft, thus protecting aircraft engines against early detonation, which can cause an engine to literally tear itself apart during operation. High performance engines are especially susceptible to early detonation / knock. It is estimated that 30% of the piston fleet are the high performance engines that would be most affected by a move to an unleaded fuel and that this 30% of the fleet burns approximately 70% of the total fuel used by General Aviation.
The past 20 years of research has been focused on finding a suitable replacement for 100LL. At present there is no viable, drop-in replacement for 100LL. And although several different companies will continue research toward this goal, we are now in a situation where we can no longer hold off regulation while waiting for such a fuel.
It is important that we consider all aspects of an alternative as we move towards a future unleaded fuel. This future fuel must meet the safety and performance needs of all general aviation aircraft (high and low compression engines). Also, manufacturers must be able to produce and distribute the product at a reasonable cost.
The ANPR gives the GA community an opportunity to comment regarding the possible new environmental standard and the development of a plan for identifying, evaluating, and ultimately transitioning to an unleaded fuel. This is particularly important given the technical complexity and safety implications of removing lead from aviation gasoline. Currently there is no high-octane replacement unleaded avgas available that has been approved and meets the requirements of the entire GA fleet.
Aircraft Owners and Pilots Association (AOPA), Experimental Aviation Association (EAA), General Aviation Manufacturers Association (GAMA), National Air Transportation Association (NATA), and the National Business Aviation Association (NBAA) among others will be continuing their work with the EPA and the FAA on establishing a realistic standard to reduce lead emissions from GA aircraft along a transition timeline which balances environmental benefit with aviation safety, technical feasibility and economic impact upon the GA industry.
AOPA along with the other organizations listed above have joined together as the General Aviation Avgas Coalition in order to assure safety, minimize impact on existing fleet, and ensure sustainability and growth of General Aviation as we move forward in the process to identify and transition to an unleaded avgas.
In order to achieve these goals the coalition:
Is continuing to work in partnership with FAA:
Have conducted several briefings for congressional legislators and their staff resulting in:
July 2010 - The EPA publically addressed concerns posed to the Agency by AOPA and the GA Avgas Coalition. They stated in no uncertain terms that there is no date by which lead is banned from avgas and that they will work closely with the FAA and industry stakeholders to on issues associated with potential future emission standards.
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