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For Bob Pastusek who states: Larry, I'll defer to your experience, but this
doesn't make sense-from an engineering perspective-to me.
Comment:
I am not an engineer. But I am an experienced 4-p driver that has had ice,
and not all that much ice, plug the K&N air filter and the stock Lancair
filter. When that happens the alt induction door opens, then the CHT alarms
go off. You go full rich and pull back power until the CHT's drop under
400, which was at about 20" MP in my plane. Depending on the amount of ice
on the wings I have had my IAS bleed off to <120 kts, and it gets your
attention. One time in California over the Sierras it happened big time in
60 seconds. By the time I got a hold of center it was done. And decent to
shed the ice was not an option because of the mountains below. I couldn't
climb, but luckily I could hold altitude until I had crossed the mountains
and then I descended. You fly along nose high and add a little flap to help
the nose down to keep more air going in the cowl.
Don Goetz was the chief pilot at Lancair for many years, with I believe 20
dead stick landings test flying Lancairs, and many thousands of hours. He
says he once had 5 inches of ice on his leading edges. He had a bit of a
different alt air induction system in that plane that he said worked. With
that much ice and power he could fly, so it would seem wing ice is not the
big issue. He is my partner in a real estate deal in Atlanta, so we talk a
great deal, and we have had many conversations about this problem. He knows
about it, has experienced it, and his theory is that it's the hot cowl air
that causes it, because something causes it and we cannot think of another
reason. I have talked to other long-time 4-p owners with the same
experience. Gene Hughes in Butte, Montana, and others. Hot CHT's in ice,
immediately.
Maybe we're nuts thinking its cowl air diving up the CHT's? But something
does it, and it happens when you get into ice. I am all ears on reasons and
fixes.
I am now close to flying a turbine and am very curious how it will handle
ice. I went with Chris Skoppe's cowl because it has very large induction
air ports that will handle a lot of ice before they ice over. I have ice
doors and a set of alternate induction air doors that will allow cowl air
into the induction system if the scoops do ice over. I attempted to also
get a hot leading edge on the inlet air scoops from bleed air but nobody is
doing it. Lancair says they will work it in the future, but to date nothing
has been done.
I see HUGE nifty panels for IFR flight, but no induction ice measures at all
on many turbines I have seen. I think induction ice and prop ice are the
most important ice issues to solve. Wing ice is not nearly the boogie man
that induction and prop ice are. I hope my turbine climb rate, the hot
prop, and hopefully my induction ice system will do the job. One of the
main reasons I went to a turbine was to get the climb rate to stay out of
ice, and have more power to deal with ice if (when) I get into it. I also
like 320 kts...(;->
Larry Klaas
2625 NW Ordway Ave
Bend, OR 97701-5497
Tel: 541-388-2420 Fax: 413-581-0178
Email: LDK@bendcable.com
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