Marc sent along this Q&A from the Lancair list. Don't know who the Q and A
guys are, but they're half a bubble off IMHO. See my comments below. Paul
Q: Mr. xxx foresees 100LL being phased out in the next few years, to be
replaced by 82UL. Does this sound realistic to you, and if so, what
modifications, if any, should we be making to our engines that we plan to
fly in the not too distant future? I assume the biggest concern would be
the risk from detonation due to the lower octane rating of 82UL.
A: I don't see how that could be done. There are probably 100,000 airplanes
out there that require 100 LL. I just bought an aircraft engine that
requires 100 LL. The AOPA would have a fit. All of this is supposition.
Money will do wonders. So you have to add lead to your gas. In 1973 they
said we would be out of crude oil by 1985 or some such.
Paul: There's something like 40,000 aircraft that require 100LL, but they
consume something like 80% of all avgas sold, due to high consumption
rates, and high useage of those aircraft. Adding your own lead is a
non-starter... we'd kill a lot of people that way.
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.
Paul: There's not much driving force in the third world for getting the
lead out. Their refineries aren't equipped to deliver octane without it,
and it's cheap. Unless environmental forces get organized, and figure out
how to address those issues, lead demand will continue for some time.
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.
Paul: Sounds like broad supposition to me.
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.
Paul: Avgas deliveries have been flat for many years. DC-6's haven't been
a significant contributor to avgas sales for a long time. And the round
engine guys are doing BETTER at getting spares made.
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.
Paul: Kind of what I said above, and inconsistent with this nameless
expert's 100,000 airplanes number, above.
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.
Paul: It's a matter of public record. I think the confusion arises 'cause
only seven refiners (people like BP, Phillips, Chevron, Texaco) make avgas.
But each of them make it at numerous refineries. Every refinery in the US
is capable of producing 82UL, if it chooses? Not quite, but to almost the
same extent, almost every refinery is capable of producing 100LL, if it
chooses. The economics just don't support them CHOOSING to do so, which is
something that Cessna Aircraft, in their former blind devotion to 82UL,
seemed unable to comprehend. Sad.
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.
Paul: Well, Cessna did start out that way. But their blind adherent to
82UL retired, and they're now selling 100LL required aircraft again.
Diesel has promise, but if anyone is "relying" on that promise today,
they're not meeting their fiduciary responsibility to their stockholders.
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 textbook) 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.
Paul: It takes no great sooth to say that any engineering solution is a
compromise. The questioner confuses the high
pressures inherent in diesel combustion with cetane, as a quality of the
fuel. Even very high cetane fuel (50 would be a very high cetane number,
some industrial fuel is 30 something cetane) requires heavy engines due to
the inherent way diesel engines operate. But cetane is EASY to inject at
the pump, or as the jet is loaded into the tank destined for piston use.
Cetane improver is NOT toxic like lead (in fact, some people consume cetane
improver as a recreational drug, which I can't recommend either).
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.
Paul: No. 100LL meets the MP / temperature requirements of engines
designed to take advantage of it. Certification requirements are redline
CHT at LEAN mixture, which is more demanding than rich. However, change
the CHT redline, and adapt the airframe installation to make that
achievable, and you create more headroom. Ignition systems like GAMI's
PRISM are designed to do just that.
EPA *tried* to ban leaded avgas, but the FAA fought a jurisdictional battle
and won. No goodwill from EPA was involved. The real limit to leaded
avgas is not decline in demand, as supposed above, but in the cost of
maintaining lead facilities in US refineries. The cost of retirement of
these facilities rises over time. Abandoning them sooner rather than later
is a strong driving force for refiners.
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.
Paul: Comparing avgas to these racing fuels is misleading. And their cost
is high, because substitution is difficult. Who's going to invest to meet
such a small market? Avgas volumes are significantly larger, I believe.
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.
Paul: The size of the engine isn't the determinant, the compression ratio
certainly is. And while lower CHT does reduce octane requirement, this too
is unrelated to engine size. A red herring!
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.
Paul: TEL *also* helps with detonation? What does this guy think octane is
meant to measure? A fuel's resistance to detonation.
There's a joint industry team working on the 100UL. There are several
potential solutions, but each poses its own challenges. The group
continues to work. I believe their meetings are open to the public. The
hybrid solution is yet another path that could be pursued. AOPA could be a
more effective cheerleader here, I think, but they have other priorities.
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.
Paul: Phooey. The size of the engine is irrelevant. The compression ratio
of each cylinder is the determinant. In fact, turbo'd engines have some
advantages running cooler on the lean side of peak. FADEC per se has
promise, but it's not being attained in the current products.
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.
Paul: Not sure that's right, who's tried it? As mentioned here, there's an
aftermarket Lycoming solution now.
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.
Paul: I disagree. As discussed above, there are a NUMBER of possible
solutions, though the EAA's approach, if accurately reflected here, is one.
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 from current FADEC systems, for
example, and take the control of the mixture and propeller away from the
pilot to avoid detonation. However, the rectification 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
Lycoming engines. A cam gear change is the major work required.
Paul: None of the existing FADEC retrofits require a cam gear change, nor
do the systems under development like PRISM. Where does this cam gear (?)
stuff come from?
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.
Paul: BS.