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Having sold my second ES,
and dabbled briefly with the idea of defecting to the RV camp, it now looks as
if my next project will be a Legacy. From all the research I've done, plus
some pretty convincing input from Tim Ong, it looks like the airplane to
build. As I told Tim, after looking over an RV-7A kit that a fellow in
Austin had for sale, it's like stepping out of your Mercedes and looking over a
Honda Civic.
Thinking about engines, and
the development of the new FG model, it occurred to me that the SMA turbo diesel
might be a candidate for the Legacy. It supposedly puts out 230hp for
takeoff, and can maintain 200hp up to 12,000', which would about equal the hp of
the IO-550 at that altitude. At 192 kg (423 lbs) it's not much different
than the IO-550. SMA claim a 30% advantage in fuel burn, too.
Putting the pencil to it,
however, it doesn't look viable. I did some rough calculations for a
3000-hour engine life, which is what SMA claim TBO will be for their
engine. For the IO-550, figure a $53K acquisition cost (engine, prop,
governor), which is $17.67/hr, overhaul costs (engine & prop, rough guess)
of about $12/hr, and a fuel cost of about $30.80/hr (14gph ave. @ 2.20/gal),
which makes a total of $60.47 combined cost. For the SMA engine,
acquisition cost is $80K (!! - I'm assuming this includes prop & governor,
but I don't know for sure), which works out to $26.67/hr, then add fuel cost at
9.8 gph (I'm buying their 30% less figure) at about $2.20/gal, or $21.56/hr,
plus overhaul, a complete unknown, but let's assume $30K at 300 hours, or
$10/hr, for a total of $58.23 per hour combined cost.
Bottom line is that there
is really no significant cost advantage, and for anything much less than a
3000-hr period, your total outlay will be quite a bit more with the SMA
engine. At 1000 hrs, the total out-of-pocket for the IO-550 will be about
$95.8K, including a $12K depreciation reserve for O/H; with the SMA engine your
out-of-pocket total will be about $112K. Most of us don't plan on having
our planes for 3000 hours, anyway. The only wild card I see is that if
(when?) the sudden edict from EPA comes, banning lead in avgas, the turbo diesel
might look pretty good. Noise level is supposed to be lower, since the
diesel turns its prop at 2200rpm. On the negative side, it's
still unproven as far as actually having installed, flying engines make
TBO.
I wonder what the thinking
was at Maule and Cirrus, both of whom apparently are bringing out SMA-powered
models? Maybe SMA is going to give them a better price, but I found some
references to an $80K cost for the diesel option in a Maule.
Whoof.
Thoughts?
Jim Cameron
Medina, TX
(Legacy deposit mailed)
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