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called into question the future of the rest. But now, for the time being at least, the oil price is back below $50/barrel and another, more permanent, concern is coming to the fore again.
That aviation must do everything in its power to minimise its impact on the envi¬ronment is no longer a matter for debate. Some of the leading airlines are pioneer¬ing the introduction of cleaner, non-fossil fuels. Jet engine manufacturers are vying with one another to not only meet, but exceed emissions targets. Even the piston-powered General Aviation (GA) community has a part to play, through the adoption of fuels from which lead and other pollutants have been eliminated.
Lars Hjelmberg has been interested in a cleaner, greener world for a lot longer than most people. Founder of Swedish fuel distributor Hjelmco, he developed an unleaded fuel for aviation piston engines in the 1970s and has been selling it and a successor product in Sweden for more than a quarter of a century.
He was impelled originally by a desire to eliminate one of the most harmful pol¬lutants in standard Avgas (aviation gaso¬
 
line). "Around a hundred tonnes of lead enter the air of Europe every year because so few piston-engined General Aviation aircraft are using unleaded fuel," he says.
The unleaded fuel that Hjelmco dis¬tributes across Sweden, and to a limited degree in a few other countries, has a medium-octane rating. But many engines need a higher rating, a demand conven¬tionally met by 100LL (100/130-octane) leaded fuel. "We have flown a high-octane unleaded fuel meeting the 100LL stan¬dard and have tested its environmental qualities to the satisfaction of a European civil aviation authority," says Hjelmberg. "It also has a biological component - anoth¬er of our strategic objectives is to make a fuel that's as close as possible to carbon dioxide-neutral."
So why isn't unleaded Avgas taking Europe by storm? Regulation, economics and politics all have a part to play in hold¬ing back the broad adoption of unleaded fuel by the European GA community, Hjelmberg maintains: "The certification process is complex, we're a long way short of the critical volumes of production that will yield a reasonable return for suppli¬ers and attractive pricing for users, and there seems to be a lack of political will to facilitate a transition to unleaded."
Hjelmco certificated its medium-octane, second-generation unleaded fuel in 1991
 
and it's still the only one on the market. The company's high-octane product entered regulatory scrutiny at ASTM Inter¬national, formerly the American Society for Testing and Materials, two years ago. The relevant standard, called D910, covers the existing approved grades of Avgas
- grades 80, 90, 100 and 100LL - and is used by the FAA when it grants engine and airframe type certificates.
An ASTM technical committee is tasked with incorporating the Hjelmco high-oc¬tane unleaded fuel into D910. Despite the existence of a 400-page report from a ma¬jor US airframe manufacturer backing the company's bid for approval, which would allow it to be used as a blanket substitute for 100LL, there is currently no published timetable for completion of this work.
Aircraft certification is also a significant hurdle. "Fuels have to be specified not only in the engine-type certificate but also in that of the aircraft itself," Hjelmberg explains. "But the majority of the aircraft in Europe certificated to use leaded fuel are in fact powered by engines cleared by their manufacturers for unleaded."
The answer, Hjelmberg maintains, is a change to the rules so that if an engine is certificated for unleaded the airframe should automatically have the same sta¬tus. "The issue is understood by bodies like EASA [European Aviation Safety Agency]," he declares. But it is a question of jumping through more hoops.
The hard economics of fuel distribu¬tion also come into play. Currently, the vast majority of GA fields have a single fuel tank - for 100LL leaded Avgas. "In any future transition from leaded to
　
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