Bob Warner, left, confers with Harry Zeisloft, center, who led EAA’s autofuel testing program, and the now late Jim Barton, who logged
hundreds of hours in a Cessna 150 in the early 1980s to demonstrate the viability of autofuel in general aviation aircraft.
A mountain of research over the past 25 years guides
these decisions. The EPA has shown a willingness to
accommodate and understand research before forcing a
change for aircraft.
“We’ve got to remember that we’ve won, in a way, by
delaying this change for all these decades,” asserts Law-
rence. But that doesn’t mean the transition will be easy.
“There’s no silver bullet. If there was, it would have been
found by now. A wide range of chemicals and compounds
have been studied by experts in both industry and aca-
demia, and the government verified the testing.”
The bulk of the latest research is coordinated through
the Coordinated Research Council (CRC) Unleaded Avgas
Development Panel. More than 60 members from 40
organizations serve on that committee, which released
its latest report on 30 unleaded blends in April. The
conclusion states, “Although full-scale engine tests indi-
cated some blends were capable of providing knock-free
operation in the test engine, those blends represented
the use of specialty chemicals which require further
evaluation with respect to environmental impact. Eco-
nomic viability of the blends tested…will also need to be
evaluated separately by industry.” The report continues,
“Although experimental blends of specialist components
may achieve or exceed the 100LL specification of 99. 6
MON minimum, such formulations…potentially compro-
mise other important specifications.”
As industry tries to match that motor octane num-
ber (MON), Lawrence sees three sets of options. The
first simply leaves out the lead and satisfies the needs
of 70 to 80 percent of the fleet. The second option, for
the remaining high-performance pistons that use the
majority of the avgas produced, “is using some of the
unfriendly additives we’ve identified.” Those are expen-
sive, but a tolerable cost might be found that allows an
unleaded fuel to be produced with high enough octane
performance to satisfy the needs of most of the remain-
ing aircraft.
