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Hiya Scott,
Good info on glide ratios. You advocate stopping the prop. In most cases,
this would produce slightly less drag than a windmilling, but high angle (prop
control pulled back) prop. Problem is, I don't think that it can be done in our
planes. I know for sure that I can't do it in our 320...I've tried. With the
engine shut down and prop back I've slowed to just above a stall and the prop
just keeps going. I've got an MT prop which will go to a higher angle than most
others, maybe this is why. Has anybody been able to stop a prop (assuming no
engine damage and a non-feathering prop in any kind of Lancair?
My guess is that in an actual emergency, it would probably be best not to
attempt it. Speaking for myself, I've got just so much concentration and the
prop stopping maneuver would use up a bunch. When thinking about engine out
procedures we always think about maximizing the glide. This is, of course, the
proper thing to do to give you more time to think and plan. There are times,
however when it is advantagious to MINIMIZE the glide ratio. Pushing in the
still spinning prop will allow you to do this.
When I was an examiner I conducted hundreds of private and commercial
flight tests always including a simulated forced landing. Getting too
high was just as common as a too low and the actual outcome would
likely be worse. Having the ability to shove the prop forward gives you one
more tool to modify your descent. That option is not available if the
prop is stopped (the possible exception would be a feathering prop with an
accumulator).
I agree with Bill Kennedy. Learn how YOUR airplane glides and practice
simulated forced landings. In our 320 with the engine at idle and the prop full
aft I get a descent rate down of 500 fpm at 110 kts. With the
engine SHUT DOWN it's 900 fpm. My suggestion would be to learn what
your airplane does with the engine actually shut down, obviously at high
altitude, good weather, and over an airport with a long runway. Once you have
that number, you can do your engine out practice with the engine at idle and the
prop adjusted to the RPM that gives you the same rate of descent that you
discovered in your shut down test. Your practice then should give you very
realistic glide performance.
Bill Harrelson
N5ZQ 320 1,750 hrs
N6ZQ IV under construction
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