Bill,
Thank God somebody actually tries this stuff (uh, somebody with your
piloting skills). Perhaps you are using Marvel Mystery Oil to reduce
engine friction..........
Is your MT prop electric? My understanding is that oil pressure
managed props (non-feathering) would go to a flatter pitch as the
pressure is diminished and the prop slows - perhaps the flatter
pitch keeps the prop from actually stopping?.
I think I only suggested that those with a fixed pitch prop try to stop it
(yes, a dangerous maneuver). Of course there is no choice if the engine
seized. I haven't flown a fixed pitch prop airplane since 1998. The
fixed pitch prop Cozy MkIV flier I know said that there is a range for his
airplane - a two bladed prop can be stopped at around 90+ Kts and will stay
stopped until around 115+ Kts. Of course it comes to a stop with the
blades horizontal in the wing wash (ah, pushers). He now has a
three bladed prop and he doesn't know if it can be stopped.
Let's try this then - CS fliers have an option of pitch control and should
know the descent rate at best glide for the extremes. I would say
that a stoppage from seizure would be some in between. Fixed pitch fliers
(and others) should know the rotten descent rate they get with the
prop in cruise pitch and windmilling and use that for rule of thumb
range estimates. Uh, 1000 fpm at 5000 AGL = 5 minutes and at 120 KIAS
that's 2 NM per minute - ergo <10 NM depending on the wind or about a 10 to 1
rate (distance to altitude). Here is where GPS ground speed is
useful. In other words, at least know the worst case descent rate.
Your final paragraph is "spot on" and there are many ways
steepen the descent - wheels out, flaps down, prop to flat pitch and/or
entering a slip. Oh yeah, a 300 series slow-speed flaps-out slip can
lead to the nose bobbing up and down. As others have mentioned, gear
up landings on a hard smooth surface don't need much "roll-out" - and note that
it will turn away from the exhaust pipe side since the metal slides
easier than glass (believe me, I know).
Do what ya can to know your airplane...
Scott
In a message dated 12/18/2009 9:20:00 A.M. Central Standard Time,
n5zq@verizon.net writes:
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