Mr. Braly,
The air cooled aircraft engines from the 1940s to the 1980s, the lower
end hp engines on small aircraft were made to run on 80 octane; C-150;
C-172s, small Pipers, other small aircraft. Your assertion 94 octane is
needed is not supported by past history.
I would say that a problem exists with the UND octane tests to say
that an octane problem exists with 80 octane avgas. The small aircraft
use history from the 1940s to the 2000s refutes this supposition.
Small aircraft with 4 cylinder engines did not fall out of the
sky due to exhaust valve failure from the 1940s to the
2000s; using leaded avgas.
Your logic has holes. Sorry! Your facts are not supported
by past aircraft engine use history! And neither is UNDs!
And I will trust what I personally observed in my 172 using
unleaded auto gas over all the reports you have cited.
Unleaded auto gas will have 4 cylinder air cooled engines
losing exhaust valves, one cylinder at a time. The history of
these loses is irrefutable, if you do any amount of checking.
Nice try! Studies that do not perform real
tests over at least 400 hours of flight time
preferably 1000 hours of flight time; have
no basis. And just unleaded auto gas in
the aircraft tank is necessary for testing.
The tests need to be done with probably
over 2 dozen small aircraft in different
climates.
What ever the additions in the new supposed
unleaded avgas, need to be proven; as detailed
above. But it is a waste of time since only
240,000 small aircraft exist in the US and
maybe that many on the rest of Earth.
Spread over the entire US, leaded avgas is
not a problem compared to other air contaminants
like volcanic eruptions, have more lead from them
than all of those 240,000 aircraft in a year.
Small aircraft fly maybe 35 hours per
year on average; nothing compared to auto use.
Only Van Nuys Airport has enough small
aircraft traffic to warrant measuring lead
from aircraft engine emissions to the
atmosphere in the US; and probably
on Earth; to know what the lead level
is near and on the airport.
With something with severe outcomes
as changing small aircraft avgas; in this
case no change is warranted; probably for
another 50 years; if ever.
Battery powered aircraft will likely be taking
over the skies over the next 100 years. And
air cooled small aircraft engines using leaded
avgas will be an insignificant anomaly in the
big picture.
And for military ops; leaded avgas will always
likely be around for them. And it should be for
such a small number of private small aircraft.
Priorities matter; and yours like the rest
of the environmental community to not
consider all of the relevant facts as listed
here. Get real. All the facts matter.
Terry D. Welander
Professional Engineer
email: tdwelander@gmail.com