Options for Reducing Lead Emissions from Piston-Engine Aircraft

The U.S. general aviation (GA) sector has a fleet that consists mostly of piston-engine aircraft. The vast majority of piston-engine airplanes and helicopters are powered by aviation gasoline (avgas). Nearly all of the country’s approximately 170,000 active piston-engine aircraft burn a grade of avgas, designated “100LL,” that contains lead. The number “100” refers to 100LLs octane rating and “LL” stands for “low lead.” Lead is added in the form of tetraethyl lead to 100LL to achieve the octane rating needed for the safe operation of those high-performance aircraft with high-compression engines, which account for about one-third of the fleet and an even larger percentage of fleet fuel consumption. Because 100LL can be used by all kinds of piston-engine aircraft, this single grade is the only type of fuel consistently available to GA aircraft operators. Consequently, 100LL is also the only fuel that most existing piston-engine aircraft are certified to use by the Federal Aviation Administration (FAA). A highly toxic substance, the Centers for Disease Control and Prevention (CDC) concluded that there is no known safe level of lead in blood. Since the use of lead additives in automotive gasoline was banned in 1996, avgas has become the country’s primary source of lead emissions. For more than 25 years, FAA, the GA industry, and fuel developers have been searching unsuccessfully for an unleaded “drop-in” replacement fuel for 100LL that can satisfy the performance requirements of the entire piston-engine fleet, including those high-performance aircraft that require avgas with an octane rating of 100 or higher. During that time, the American Society for Testing and Materials (ASTM) adopted specifications for a second grade of leaded avgas, 100VLL (“very low lead”), which has the same octane rating as 100LL but nearly 20 percent less lead. In addition, ASTM issued specifications for unleaded (UL) avgas with lower octane ratings, which can be used by lower-performance aircraft. While only one fuel, UL94, that meets the ASTM specifications for unleaded avgas is currently produced, and is available at a select number of airports, 100VLL is not being produced. Section 177 of the FAA Reauthorization Act of 2018, called on FAA to commission this study by a National Academies committee. The study was to consider (a) ambient lead concentrations at and around airports where piston-engine aircraft are used, (b) existing non-leaded fuel alternatives to avgas used by piston-engine general aviation aircraft; and (c) mitigation measures to reduce ambient lead concentrations, including increasing the size of run-up areas, relocating run-up areas, imposing restrictions on aircraft using avgas, and increasing the use of motor gasoline. Those mitigations could involve actions targeted at reducing lead emissions or reducing elevated concentrations of airborne lead in specific locations (hot spots). The committee came to realize that currently there is no individual, certain solution to the aviation lead problem, and therefore a multi-pathway mitigation approach offers the greatest potential for tangible and sustained progress. The pathways that comprise this approach are described and recommendations are made for facilitating their pursuit.


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Prepublication Copy
  • Features: Appendices; Figures; References; Tables;
  • Pagination: 143p
  • Serial:
  • Publication flags:

    Open Access (libre)

Subject/Index Terms

Filing Info

  • Accession Number: 01762336
  • Record Type: Publication
  • ISBN: 9780309256803
  • Files: TRIS, TRB, ATRI
  • Created Date: Jan 13 2021 1:34PM