Shell has developed a lead-free replacement for aviation gasoline (Avgas 100 and 100LL); the replacement fuel will now begin a strict regulatory approvals process. Shell is the first major oil company to do so. The new lead-free formulation comes after 10 years of R&D, as well as successful initial testing, carried out in the last two months by two original equipment manufacturers (OEMs).
Avgas is one of the last common transportation fuels—and the only fuel in the US—to contain the additive tetraethyl lead (TEL); avgas is used by light aircraft and helicopters. (Leaded gasoline for automobiles was phased out of use in the US by 1995 due to its environmental and health impact.) Avgas includes lead in its formulation to meet fuel specifications, to boost combustion performance, and to prevent knock.
|There are two main types of aviation fuel: aviation turbine fuel (jet fuel) and aviation gasoline (Avgas). Jet fuel is used by larger, gas-turbine-engine powered aircraft, while Avgas is used in smaller, piston-engine powered aircraft.|
|There are currently two main Avgas grades, 100 and 100LL (low lead). 100 is a measurement of octane rating. There are specialty grades at the low-and high end: Avgas 80/87 for low-compression-ratio engines with little or no lead, and Avgas 115/145 for high performance piston aircraft engines used in World War II and the Korean conflict. The latter is very hard to find, and is usually only produced on special order.|
|Lead emissions from piston-engine aircraft operating on leaded fuel are currently the largest source of Pb air emissions on a national scale, according to the US Environmental Protection Agency (EPA).|
|Avgas 100LL, the most commonly used avgas, can contain up to 2.12 grams Pb per gallon (ASTM D 910). The Federal Aviation Administration estimates that in 2008, 248 million gallons of avgas were consumed in the US, contributing an estimated 550 tons of Pb to the air that comprise 57% of the national Pb inventory.|
|Leaded avgas is used at approximately 20,000 airport facilities in the US.|
Shell says that its unleaded Avgas meets all key Avgas properties and has a Motor Octane rating of more than 100, an industry standard.
The development of a technically and commercially-viable unleaded Avgas that meets these criteria has been seen by the aviation industry as a significant challenge, due to the tight specifications and strict flight safety standards to which it must adhere.
To get to this stage, Shell Aviation technologists carried out an intensive internal laboratory program, including in-house altitude rig and engine testing. Working alliances were then formed with aviation engine manufacturer Lycoming Engines (Lycoming) and the light aircraft manufacturer Piper Aircraft Inc. (Piper). As a result, the formulation was successfully evaluated in industry laboratory engine (bench) tests by Lycoming and in a flight test by Piper.
Lycoming Engines commends Shell on launching its unleaded Avgas initiative. They engaged Lycoming to test their fuel on our highest octane demand engine and we can confirm that it’s remarkably close to Avgas 100LL from a performance perspective. This initiative is a major step in the right direction for general aviation.—Michael Kraft, Senior Vice-President and General Manager of Lycoming Engines
Piper Aircraft is pleased to participate with Shell and Lycoming in this feasibility flight test program. Recently, we successfully flew an experimental non-production Piper Saratoga with Shell’s new formulation for about an hour. We appreciate the opportunity to work with Shell and Lycoming in this preliminary investigation of the technologies, which could in several years lead to flying unleaded fuel in our production airplanes.—Piper Vice-President of Engineering Jack Mill
Shell will now engage the aviation industry, regulators and authorities, including the US Federal Aviation Administration, American Society for Testing and Materials (ASTM) and European Aviation Safety Agency (EASA) to achieve approvals for the unleaded Avgas. Shell expects to also work with other OEMs to continue the testing and refinement program as the approvals process progresses.
Regulatory issues. Globally, petitions and potential litigation from environmental organizations are pushing regulatory agencies to consider actions to eliminate or reduce lead emissions from aircraft.
In the US, the EPA began gathering data in 2010 prior to a presumed rulemaking on lead emissions from piston-engine aircraft using leaded aviation gasoline (avgas). (Earlier post.)
The timeline for completion of this investigation and possible issuance of a final endangerment determination includes completion of necessary modeling and monitoring information and other data, development of a proposal which will be published for public comment, review and analysis of comments received and issuance of the final determination.
If the EPA issues a positive determination that lead emissions from aircraft engines cause or contribute to air pollution that may reasonably be anticipated to endanger public health or welfare, the EPA would then be required to propose and promulgate emissions standards to control aircraft engine lead emissions, and the Federal Aviation Administration would be required to promulgate regulations addressing the fuel.
In a 2012 report on unleaded avgas, the Federal Aviation Administration (FAA) noted that worldwide uncertainty and concern exists amongst piston aircraft equipment manufacturers, avgas producers, avgas distributors, fixed base operators, aircraft owners and aircraft operators regarding: future utility and value of existing aircraft; availability and cost of aviation gasoline to maintain viable business operations; (c) justification of new aviation product development; and (d) justification of new aircraft purchases.
Marie Lynn Miranda, Rebecca Anthopolos, and Douglas Hastings (2011) “A Geospatial Analysis of the Effects of Aviation Gasoline on Childhood Blood Lead Levels,” Environ Health Perspect.119(10): 1513–1516 doi: 10.1289/ehp.1003231