GA community works to replace 100LL

Monitoring shows low lead levels around all but two airports

June 20, 2013

The general aviation community is committed to an unleaded future and has engaged in an extensive program with the FAA to transition the industry to an unleaded avgas. AOPA has joined other industry organizations in a General Aviation Avgas Coalition, working to develop a safe, alternative fuel source. In fact, the FAA recently announced it is accepting unleaded fuels for testing as possible replacements to the 100-octane, low-lead avgas GA aircraft use today.

As part of a study to attain a better understanding of how emissions from GA aircraft contribute to air quality, the Environmental Protection Agency has posted preliminary airport monitoring results indicating that 15 of the airports monitored during a year-long study have lead emissions well below the current National Ambient Air Quality Standard (NAAQS) for lead. The monitoring demonstrated that only two airports have preliminary data exceeding the NAAQS. It should be noted that these monitors were placed directly behind the run-up areas and were effectively monitoring direct emissions from the aircraft. The readings from these monitors are not reflective of levels that are normally found as distance from the aircraft is increased.  AOPA, with input from air quality experts have questioned both the placement and subsequent results of these monitors and the relevance of their findings with respect to ambient air. According to the EPA, the monitors at these two airports were situated at locations representative of the highest expected airborne lead concentrations immediately downwind of the primary runup and takeoff area. The EPA also noted that information from other airports that have been studied in greater detail indicates that air lead concentrations decrease sharply within short distances from the takeoff areas.

Through a series of actions beginning in 1973, the EPA reduced and then ultimately eliminated lead from automotive gasoline in 1996. However, lead was allowed to remain in the small amount of aviation gasoline still utilized by piston aircraft because of safety considerations. The aviation industry has responded by reducing the maximum lead content of aviation gasoline by 50 percent to the present standard in use today. As a result of these actions, there has been a dramatic improvement in air quality, and a 99-percent decrease in total lead emissions—from 74,000 tons in 1980 to 2,000 tons in 2008. And since 2008, lead emissions from avgas have dropped by another 28 percent, to approximately 550 tons per year.

The General Aviation Avgas Coalition, composed of AOPA, the American Petroleum Institute, Experimental Aircraft Association, General Aviation Manufacturers Association, National Air Transportation Association, and National Business Aviation Association, has worked with the FAA to create the Piston Aviation Fuels Initiative with the goal of facilitating the development and deployment of a high-octane fuel that will have the least impact on the existing GA fleet and distribution system.

Airports were selected for the EPA study based on factors such as the level of piston-engine aircraft activity and the predominant use of one runway due to wind patterns.

The EPA has posted the preliminary results of the airport monitoring which indicates that 15 out of the 17 airports have lead emissions well below the current standard for lead. 

Only two airports (with monitors located very close to their run-up areas) —San Carlos (SQL) in San Carlos, Calif., and McClellan-Palomar Airport (CRQ) in Carlsbad, Calif.—show data exceeding the national standard.

Monitors at these two locations will become permanent with additional monitors to be added. In an effort to better understand lead levels adjacent to the San Carlos Airport, in March 2013, the EPA, with monitoring assistance from the Bay Area Air Quality Management District, placed a monitor north of the airport. The very limited results available to date from this supplemental north monitor show levels well below the health protective standard. Efforts are also under way to further study localized impacts near the airport to determine how quickly lead concentrations dissipate.

Despite extensive efforts, no unleaded replacement has been found and approved that provides adequate and comparable safety and performance to 100LL. But work on this important issue continues and is accelerating, with ongoing efforts to study and develop alternative aviation fuels.

Most significant is the realization that a replacement fuel will not be “drop-in” thus requiring the recertification of the entire fleet of existing aircraft.  In doing so, this program will assess the viability of candidate fuels in terms of impact upon the existing fleet, production and distribution infrastructure, environment and toxicology, and economic considerations.