ABSTRACT: The Federal Aviation Administration (FAA) shares the Environmental Protection Agency’s (EPA) concerns about lead emissions from small aircraft. Owners and operators of more than 200,000 piston-engine aircraft operating in the United States rely on leaded aviation gasoline (avgas) to power their aircraft. Because of lead toxicity and environmental persistence, the FAA, EPA, and aviation and petroleum industries are partnering to remove lead from avgas.

Avgas emissions have become the largest contributor to the relatively low levels of lead emissions produced in the U.S. As a result, the Piston Aviation Fuel Initiative (PAFI) was established at the request of a broad cross section of the aviation and petroleum industries and consumer representatives to develop a path forward for the identification, evaluation, and deployment of the most promising unleaded replacements for avgas. The mission of PAFI is to evaluate candidate unleaded replacement fuels and identify those fuels best able to technically satisfy the needs of the existing aircraft fleet while also considering the production, distribution, cost, availability, and environmental and health impacts of those fuels. The FAA selected four unleaded fuels to undergo Phase 1 testing at the agency’s William J. Hughes Technical Center. Phase 1 included environmental toxicology, emissions, engine and rig performance, and materials compatibility.

This presentation focuses on the assessment framework for environmental toxicology and engine exhaust emissions. A risk-based approach was followed based largely on published toxicological data and physical/chemical properties of fuel components, comparing potential human health and ecological risks of the unleaded fuels to those of avgas. Engine exhaust emissions tests included analysis of total hydrocarbons, carbon monoxide, carbon dioxide, nitrogen oxides (NO, NO 2 , and NO x ), methane, sulfur dioxide, acetaldehyde, formaldehyde, and particulate matter. Based on Phase 1 test results, two fuels were down selected to enter more comprehensive Phase 2 testing, with the eventual replacement of leaded avgas by 2018.

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