Phase-out of Leaded Aviation Gasolines
The 100LL phase-out has been called "one of modern GA's most pressing problems", because 70% of 100LL aviation fuel is used by the 30% of the aircraft in the general aviation fleet that cannot use any of the existing alternatives.
In 1979 Swedish Hjelmco Oil developed and introduced unleaded AVGAS 80/87 to the Scandinavian market. This fuel met the US standard for AVGAS ASTM D910 valid at that time. This fuel was extensively used by the Swedish Air Force for about 10 years. In 1991 Hjelmco Oil introduced an unleaded AVGAS 91/96 UL meeting leaded grade 91/98 also in standard D910 with the exception of transparent colour and no lead. Engine manufacturers Teledyne Continental Motors, Textron Lycoming, Rotax and radial engine manufacturer Kalisz have cleared the Hjelmco AVGAS 91/96 UL which in practice means that the fuel can be used in more than 90% of the entire world piston aircraft fleet. AVGAS 91/96 UL has been produced in Sweden since 1991 and used in thousands of aircraft for many million flight hours. In November 2010 the European Aviation Safety Agency (EASA) based on about 20 years of trouble-free operations with unleaded AVGAS 91/96 UL produced by Hjelmco Oil cleared this fuel for all aircraft where the aircraft engine manufacturer has approved this fuel.
In February 2008, Teledyne Continental's new president, Rhett Ross, announced that the company is very concerned about future availability of 100LL avgas, and as a result, they would develop a line of Diesel engines. In a February 2008 interview, Ross indicated that Continental Motors believes that the aviation industry will be "forced out" of using 100LL avgas in the near future, leaving automotive fuel and jet fuel as the only alternatives. In May 2010 Continental announced that they had licenced development of the SMA SR305 Diesel engine.
In November 2008 National Air Transportation Association President Jim Coyne indicated that the environmental impact of aviation is expected to be a big issue over the next few years and will result in the phasing out 100LL, due to its lead content.
By May 2012 the US Federal Aviation Administration had put together a plan in conjunction with industry to replace leaded avgas with an unleaded alternative within 11 years. Due to progress already made on Swift fuel and G100UL the replacement time may be shorter than that 2023 estimate. Each candidate fuel will have to meet a checklist requirement of 16 items that include 12 fuel specification parameters and four distribution and storage parameters. The FAA has requested a maximum of US$60M to fund the administration of the changeover.
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