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Fred,
You hit on a big one. I'll tell you what I know. It's not much more. You
took good notes.
Q--* Tetraethyl lead (TEL) is produced in only one plant in the world in
the UK. The firm operating this plant [Octel. Inc.] bought the plant in
East Germany and shut it down. [Confirmed.] The plant in Chechnya is
unlikely to resume production anytime soon.
A-- I can confirm this. It comes down to money. Is it profitable?
Q--* The last corners of the world using leaded motor gas will cease doing
so this year thus completing the worldwide removal of leaded fuel from the
motor gas pool.
A--This will happen but farther out than the end of this year.
Q--* Demand for TEL is dropping 15% per year.
A-- I heard 10%. But still, it's dropping fast!
Q--* 100 LL will be phased out between 2005 and 2010. The regular
production of TEL will cease in 2005 and 100 LL after that date will use
stored supplies of TEL. [I found the Octel web site and sent an e-mail
asking for confirmation.]
A-- I cannot confirm this but it sounds reasonable to assume.
Q--* Usage of 100LL is dropping rapidly. The large engine piston fleet is
being retired in favor of turbine engines in corporate and commuter use, and
old freighters like DC-6's are also being retired due to lack of spare parts
for big round engines.
A--True, the commercial market is getting smaller.
Q--* About 70% of the general aviation fleet can use 82UL.
A--I would say 80%. But that 80% only use 20% of the 100LL.
Q--* FBOs only want to stock one type of fuel because of the cost of
equipment and inventory. So they stock what everyone can use -100LL.
A--True. We must have a single fuel option to be viable.
Q--* Only seven refineries in the U.S. can produce 100LL, while every
refinery in the US (about 400) is capable of producing 82 UL today, if it
chooses.
A--Not sure on the exact number but seven sounds close.
Q--* Cessna's approach has been to use low compression engines capable of
using 82UL for lower horsepower applications, and rely on new diesel
engines for higher powers for future larger aircraft.
A--I heard this also. High power diesel(jet A) piston aero engines are five
years away minimum.
Q--* Diesel engine progress has been poor because aero diesel engines must
use jet fuel. Jet has a much lower cetane rating than diesel fuel. This
leads to higher peak pressures in the engine (somewhat like knock)resulting
in heavy engines, [confirmed in Taylor's classic text book] and so far they
will probably be too heavy for use in current
aircraft. Additives can raise the cetane rating of Jet fuel, but the cost
adder is unacceptable to turbine engine operators. So a high cetane jet
fuel blend would have to be separately produced and stocked. But recall from
above that FBOs only want to stock one fuel for piston engines.
A--True it is not the answer for every installation. Jet A fuel poses some
problems but the GAP engine will address them. The base GAP engine will be
equal in weight to a comparable 200 bhp engine(TCM IO-360). The weight
penalty comes from the cooling system and turbocharger. But adding these
features is not an apples to apples comparison. Liquid cooling reduces
cooling drag and turbo normalization gives altitude performance. It will
be a compromise in the end for sure.
Q--* 100 LL is actually about 102-104 octane (motor method), and this high
level is needed because of high possible cylinder head temperatures (in some
cases combined with high manifold pressures in turbo'ed units) in air cooled
engines. Certification requires that these must operate up to red line CHT
without detonation when full rich.
EPA and the regulators are not trying to ban leaded avgas because the
industry is working on the problem. However, it will be effectively banned
sometime after 2005 as the demand drops and price reaches such high levels
that it is effectively no longer available.
A--This is a very clear picture of things to come.
Q--* [Refineries can make high octane unleaded fuel, but at prohibitive
prices. Unocal has a limited number of outlets for racers in the Los
Angeles area, but fuel costs are typically $5-6 per gallon without taxes
since these are not road fuels.]
A--This would only address part of the issue.
Q--* Every 20F drop in cylinder head temperature reduces the engine octane
requirement by approximately 2 points. Smaller four cylinder engines in the
160 to 180 HP class can use 82 UL today.
A--I cannot confirm this exact number on TCM engines. But the lower CHT
allows lower octane requirements.
Q--* There will be an unleaded Avgas produced to replace 100 LL, but it
will not be as high octane as 100 LL. It will probably be a low vapor
pressure formulation that will be around 94 octane tailored to meet
technical and cost requirements.
A--TEL also helps with detonation and lubrication of the upper cylinder.
The oil industry has not developed a fuel which can directly replace 100LL.
It must be a hybrid solution involving the fuels and engines.
Q--* Consequently, larger engines, 200 HP and up, 500 cubic inches and up,
and turbocharged engines have an uncertain future past 2005 as 100LL
supplies dry up and the price skyrockets.
A--All indications show this to be true. FADEC offers hope on the engine
side.
Q--* Liquid cooled engines can operate with much lower octane because of
lower combustion chamber temperatures. Lowering head temperatures from 400F
to 200F can reduce the motor octane rating as much as 10 points, down to
92-94 octane. [However, details of combustion chamber design can also be
important.]
A--Liquid cooling does offer a partial solution but is impractical as a
retrofit on most airframes.
Q--* In the opinion of the EAA representative, the only solution is "modern
engines, liquid cooled, with electronically controlled fuel injection and
ignition systems such as those that have been demonstrated to run
[efficiently] on 92 octane auto fuel today."
A--I agree.
Q--I conclude from this that the long term future of Continental TSIO-550's
in Lancairs and TSIO-540 Lycoming engines in Malibus is dim indeed. UNLESS
the engine manufacturers produce retrofit packages for the existing fleet of
engines. Perhaps these would be derived form current FADEC systems, for
example, and take the control of the mixture and propeller away from the
pilot to avoid detonation. However, the recertification problems in all the
different air frames would seem to be immense.
A--The current high BMEP engine's future using 100LL is uncertain. FADEC
offers a partial solution with its knock sensing capabilities and timing
control. FADEC will be retrofittable relatively easily to all TCM and Lyc.
engines. A cam gear change is the major work required.
Q--Are current generation certified turbocharged high performance piston
engine airplanes endangered species?
A--The High BMEP engines we know and love today will be history in 10 years.
So says my crystal ball.
ERic--
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LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
LML Builders' Bookstore: http://www.buildersbooks.com/lancair
Please send your photos and drawings to marvkaye@olsusa.com.
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