Aviation Gasoline – Getting the Lead Out
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 aviation gasoline (avgas) to power their aircraft.
Avgas is the only remaining lead-containing transportation fuel. Lead in avgas prevents damaging engine knock, or detonation, that can result in a sudden engine failure. Since lead is a toxic substance that can be inhaled or absorbed in the bloodstream, environmental organizations have petitioned EPA to remove it from avgas. Avgas emissions have become the largest contributor to the relatively low levels of lead emissions produced in this country.
The FAA and EPA work together to curb the use of lead in aviation fuel. The Clean Air Act requires that EPA consult with FAA when issuing proposed emission standards for aircraft, and EPA is prohibited from issuing those regulations if that consultation reveals an adverse impact on safety or noise. On the other hand, FAA may prescribe standards for aviation fuel, but only if EPA determines that aircraft emissions from the fuel endanger public health.
To help EPA "get the lead out," FAA is supporting the research of alternate fuels at our William J. Hughes Technical Center in Atlantic City. We are working with the aircraft and engine manufacturers, fuel producers, and industry associations to overcome technical and logistical challenges to developing and deploying a new, unleaded fuel.
The FAA airworthiness certification approval to use a new, unleaded fuel is a key element of the deployment challenge. Aviation fuel is certified by FAA as an operating limitation of both the aircraft and the engine. If a new fuel can be developed that falls within the existing aviation fuel operating limitations of the legacy fleet of aircraft, then FAA approval is easy. However, if new operating limitations are required, then a major design change approval would be needed for each aircraft and engine model.
Where do fuel specifications fit into these approvals? The operating limitations must be defined in a manner that ensures that the fuel is controlled to the extent necessary for safe operation. This is typically accomplished with an industry consensus-based fuel specification, such as those written by ASTM International. However, an alternative fuel specification is acceptable as long as it provides the necessary level of control of the fuel composition and properties.
Several possible solutions are being investigated and FAA is playing a key role. As an interim step, we are evaluating ultra-low lead fuel that can be seamlessly incorporated into the supply chain without the need for engine modifications or re-certification. Longer-term solutions involve investigating both new fuel formulations and engine design characteristics in an effort to look at the problem from both perspectives.
The FAA continues to work with EPA to make this a smooth transition and to ensure the supply of aviation gasoline is not interrupted, and that all aircraft can continue to fly.