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I will try to address the questions raised by Scott Turner and others
concerning the EngineAir power plant. First, a disclaimer: I am an
EngineAir customer and so have obviously made a decision, so bear my
likely biases in mind. However, I also like to focus on facts where
available, or make reasoned speculations based on laws of physics (or
economics) where facts are not available. Summary: I believe that
control of risk rests primarily in your hands as a builder and pilot,
not in the engine, wherever it may come from. Focus on your own
designs, practices and execution for the best improvement in
reliability.
First, the issue of fuel burn. (Forgive me for covering some old
ground. This may be new for some new folks.) Operated at an optimal
economy fuel/air mixture, (a bit lean of peak at a moderate cruise power
setting) the Continental and EngineAir packages should (and do) have
roughly the same efficiency. The EngineAir unit, being liquid cooled
(180F cylinder head temperature versus 400F) can run a bit higher
compression ratio which helps efficiency a bit, but only a bit.
HOWEVER, the reality of day-to-day operation with the Continental
TSIO-550 has been premature exhaust valve and cylinder wear which is
presumably due to ham fisted mixture and throttle control by pilots.
George Braley has made an excellent case for why lean of peak operation
should be in all ways better. But the experience in the field has
caused the Lancair factory to recommend in its newsletter that one
operate the Continental full rich in take off and climb, and 100F rich
of peak otherwise to avoid the problems that have been observed. And
cruise at 65% or less. Yet we know that all Lancair IV pilots are the
cream of the crop, so we will assume that all of them will, henceforth
operate with the mixture control at the optimal economy setting, lean of
peak, at cruise. Under these conditions, the fuel burn of both engines
should be about the same, perhaps a trifle better with the EngineAir due
to a bit higher compression ratio since detonation is much less a
problem when liquid cooled.
So at this point, gallons per hour, ideal conditions, call it a draw.
It is up to the pilot to handle the red knob of his Continental so as
not to cause a $10,000 problem in 600-800 hours. (It has happened many
times, so be careful, y'all.) On the EngineAir package, one of the dual
computers handles the task with the electronic fuel injection system,
and the liquid cooling puts metal temperatures, particularly around
exhaust valves and their seats (and the turbo, also liquid cooled) much
lower than with an air cooled engine. Lifetime of hot parts improves
accordingly. Pistons fit better in cylinders. Oil is cooler on the top
end parts and cylinder walls. And so on. If it is cooler and fits
better, it should last longer.
Now consider the cost of the gasoline you pump into your wings. Dyno
testing with the EngineAir package has been done with 93 octane auto
fuel suggesting it can be used safely. But the EngineAir President and
Technical Guru, Al Joniec has correctly noted that a lot more testing is
probably required in the field to confirm that 93 octane can be used
under all conditions (read hot, high altitude, maximum manifold
pressure). The problem, if it occurs, is likely to be the variability
of auto gasoline by region, and looser quality control standards
associated with motor gas. (Buy fuel for your Lancair IV at Rotten
Robbie?). If you back the throttle down from 440 horsepower to (say)
350 horsepower, you will probably never have a problem with auto gas in
the EngineAir package. But that is MY OPINION, and needs to be
supported by a lot of tests in different airplanes with lots of
different gasoline.
ASSUMING that test results support theory and 93 octane is as safe and
reliable as 100 LL in the EngineAir package, THEN you can compare the
cost of auto fuel and avgas, figure how many hours you fly per year, and
figure the savings yourself. If you use 18 gallons per hour for cruise
power, $2.50 per gallon for avgas, and $1.50 per gallon for premium auto
gas, you save $18 per hour, and for 100 hours per year, you save $1800.
Fill in your own numbers and compute your own answer. If you plan to
run your Continental as the factory recommends (fuel-cooled), plan 20+
gallons per hour of avgas, and re-compute.
With regard to reliability, in general with a good development program,
more experience should equal more reliability. Since Continental has
huge amounts of experience (thousands of engines and millions of hours),
their reliability should be the best available, unexcelled, outstanding.
But there seems to be a bit a problem with things like broken
crankshafts (Lycomings also) that are, in my book, unforgivable for a
company like Lycoming or Continental. It brings their entire quality
control and supplier management program into question. Remember also,
the Extra 400 threw a rod on a factory demonstrator and ended up on a
freeway. How do these things happen with very mature engines? It makes
one stop and wonder a bit.
But I still have to believe that if you examine the engine alone, and if
you could collect and digest the data (not available, unfortunately),
the reliability should be greater with the older, more mature engines.
Should be.
But this is only a part of the reliability issue. A small part, I
believe.
I am willing to bet that a careful analysis of engine failures on
experimental aircraft would show OVERWHELMINGLY that the vast majority
are due to construction or installation errors, that is, poor builder
design or execution. Make a mistake, flame out the engine. For every
crankshaft that breaks or connecting rod that departs the aircraft, I
bet there are 10 (maybe 100) failures due to: clogged fuel filters,
leaky fuel lines, improper wiring, swelling o-rings jamming fuel
selectors, exhaust leaks melting something, cracks in oil coolers
dumping oil overboard, and on and on and on.
That being the case (and I believe it is the case, although sadly there
is probably little reliable data to prove it), if you want RELIABILITY,
then STARE IN THE MIRROR. In exactly the same way that most fatal
accidents are due to poor pilot judgment (running out of fuel, VFR
flight into IMC, night disorientation, zooming your girlfriend's house,
descending below minimums, etc.) and are thus pilot controlled, I
believe that nearly all reliability (and safety issues) are also in the
hands of the builder, the quality of his execution, the degree of his
care, and his planning and inspection skills. ENGINE INSTALLATION trumps
the engine alone.
If you put engine reliability at the top of the list, I suggest you are
making a mistake. Put the pilot's skill, competency, planning, and
judgment first, second, and third, and follow with your builder's skill,
competency, planning and judgment. And fly as if it WILL fail, and be
prepared to deal with it. I believe THAT is the best way to stay alive.
Other issues fade in comparison and importance.
These are my opinions based on watching general aviation for 40+ years.
If you have data that suggests other priorities, please share them with
the rest of us. Reliability is YOUR responsibility. When you make a
dead stick landing, it is likely you caused the problem.
Fred Moreno
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