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Posted for Walter Atkinson <walter@advancedpilot.com>:
Marvin:
You say that cruise efficiency and speed are at the opposite ends of the
spectrum, but that's not really exactly true. You can go too slow for max
efficiency as well. Absolute max range is found at LDmax. I don' know that
exact speed in a Lancair. In a Bonanza, it's about 100 knots TAS. The first
step in extending range should be to set the mixture at BSFC(min). At high
powers that will be as far as 70dF LOP. At very low power settings, BSFC(min)
will be at about 10dF LOP. The next step in extending range should be
reducing rpms, still keeping WOT. (the engine is more efficient at WOT than
any reduced throttle setting). The very last step would be to reduce
throttle.
In the IOF-550, the way TCM has designed and programmed FADEC, these options
are not available to the pilot. You have no mixture control. It seldom sets
best economy, since it sets the mixture at a pre-programmed, not optimal
setting. The only choice is to reduce power... the least desirable option if
efficiency is the goal.
Walter Atkinson
Jabe Luttrell
I think you will find that on paper the Legacy with the IOF550 will fly 2000 miles non-stop (no winds) with the basic tanks. You just have
to slow down...a lot. With about 30% power you'll burn about 5.6gph and go 199mph. With 60gallons capacity that's 2132sm.... nearly 11 hours.
[ Jabe is head of engineering at http://www.fadec.com/
and Legacy builder -Rob ]
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