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Fred,
>>Hence the recent EAA initiative
to breathe life into a 91-96 unleaded avgas proposal.<<
Ah... Fred let me please, set the record straight on that.
I was **** NOT **** REPEAT **** NOT ****
an EAA initiative. The recent re-activation of the old ASTM 91/98
(sometimes called 91/96) specification was done at the specific request of
GAMI.
At GAMI's request EAA supported the effort. If they had opposed it, it
probably would not have happened. With their support it did happen. But
the idea to do it and the initiative to get it done came from our
certification effort on PRISM. I thank EAA for the time and effort they
did devote to helping to get that done.
I hope it doesn't backfire on all of us.
Here is the history on that:
Some 30 months ago, GAMI went to FAA and said we want to certify our new
ignition system on unleaded fuel. We want to use a straight 100LL fuel, but
without the lead package as our "defined" or "specified" fuel for
certification.
The FAA said, "...NO" you *CAN NOT* do that under the regs... you have to
have an officially recognized (by ASTM) fuel spec. (And, never mind that
that statement turned out not to be correct information from the highest
levels of the FAA...)
So we asked ASTM to make an alternative to the 100LL spec, called 100LL- WTL
- - without the lead.
ASTM said that will take six years, but, have we got a deal for you, we can
reactivate the old 91/98 specification, and that will only take 18 months.
We said, fine, lets do it. And, so, a few months, back, they finally got
it done.
[ As an aside: You might like to know that, last Wednesday morning, some
of the policy folks (as distinguished from the writers for the magazine)
from AOPA were in Ada, and watched PRISM run the TIO-540 J2BD to 353 Hp, on
91/96UL (91/98) with the CHTs all above 460F and the hottest CHT at,
exactly 500F. Free of detonation.]
All that said, what we really need is a good 95octane unleaded avgas.
And guess what? Chevron makes such a fuel, right now. Today.
In fact, you have probably already run some of through your tanks... well
sort of.
Every time you buy a gallon of 100LL from Chevron that came out of its
Mississippi refinery, you get a fuel that, routinely, without the lead,
will have 95 to 97 octane. There is no magic to this. No special
additives. Just good practices and management in the refinery, which is, by
all accounts, one of the better operated and managed refineries around the
country.
>>The refineries can make this, and to aviation specifications. It is
usable in about
90% of the piston engine fleet.<<
No... not really, and it is worse than that. Remember, 70% of the fleet
burns 30% of the fuel.
30% of the fleet burns 70% of the fuel. The 30% of the fleet that burns the
majority of the fuel includes a lot of the aircraft that CAN NOT live on
91/96 without hardware changes.
If you want to see avgas fuel prices skyrocket, just ground the 30% of the
fleet that uses 70% of the fuel. The remaining market will be so small that
it will not be worth pursuing by the refiners.
My estimation is that about 40 to 50% of the fuel burned is burned in
engines that cannot, unmodified, operate on 91/96.
Derating is not an option, as it would ground all of the twin engine fleet
(single engine rate of climb, issues).
>>The engine manufacturers are probably praying for a FADEC breakthrough to
control detonation. I
wouldn't hold my breath for such a breakthrough to occur. But George seems
to be on the right track with his research.<<
Ah.. Fred... you are invited to come by Ada. This is no longer "if it works
research". We have done the research. It works.
See the comments in brackets [ above ].
At this point, we are furiously working on packaging this whole thing to get
it ready for market.
>>To me, a world of lower
octane fuels means a requirement for much lower cylinder head
temperatures (20F decrease in CHT is roughly equal to 1 octane number
reduction) which means liquid cooled engines.<<
It cannot be done (economically) and retrofitted on the certified airframes,
so that is a non starter as a solution.
Have you seen the price of the liquid cooled option for the twin Cessna?
And, further, just because the coolant temperature is 190F or 240F, doesn't
mean that the cylinder head temperatures are also 190F or 240F.
Regards, George
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