GRAHAM WARWICK / WASHINGTON DC
Specification provides unleaded alternative for 90% of general aviation piston fleet
With the unleaded aviation gasoline burned by most piston aero-engines expected to be phased out over the next decade, industry has reactivated a fuel specification that provides an unleaded alternative for most light aircraft.
The American Society for Testing and Materials International, which sets fuel standards, has reintroduced the specification for 91/98-grade aviation fuel. This can be refined as an unleaded product to replace the current 100-octane low-lead (100LL) avgas used by the majority of piston-powered general aviation aircraft. Limited quantities of 91/98-grade unleaded fuel are already being produced in Northern Europe.
Reintroduction of the 91/98 specification, removed in 1968, is viewed as a safety net as industry continues to work towards the replacement of lead in aviation fuels. The US Experimental Aircraft Association (EAA), which led the task group that revived the specification, estimates that more than 90% of the general aviation piston fleet could use the fuel safely. Engines as large as 135kW (180hp) could use it without modification.
The remaining 10% is mainly larger piston twins with higher-power piston engines that need higher-octane fuel. "This specification can safely and efficiently serve the bulk of small aircraft powerplants and airframes," says Earl Lawrence, EAA vice-president of government and industry relations.
Source: Flight International
