BobsV35B(at)aol.com
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 Posted: Tue Mar 03, 2015 1:19 pm Post subject: Stopped Prop? |
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Good Afternoon 'Lectric Bob,
As an old glider instructor and tow pilot, I have spent quite a bit of time trying to get a prop stopped in flight. There are a few that will stop with no heroics once the go juice is taken away, but most are very hard to make stop turning. A Piper Cub with a wood prop can be stopped relatively easily by slipping a bit just before it stalls. With a metal prop, it may or may not be able to get it stopped.
On early Bonanzas, I was almost always able to get it stopped by placing the electric prop for maximum pitch, minimum RPM. That did not ALWAYS work, but it did often enough that I was able to demonstrate soaring flight in a Bonanza on days where the lift was excellent.
Soaring a Bonanza will convince most would be glider pilots that there is a lot of rising air out there if you know how to find it. I have been unable to get my current IO-550-B engine to stop spinning regardless of how hard I have tried.
Obviously, such shenanigans should only be undertaken where conditions are extremely favorable!
One of our granddaughters has a Legend Cub powered by the Jabiru engine. That bugger will quit on final unless the power is set so high that it stretches the glide on final!!?
As Always, It All Depends!
Happy Skies,
Old Bob
In a message dated 3/3/2015 2:28:45 P.M. Central Standard Time, nuckolls.bob(at)aeroelectric.com writes:
| Quote: | --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
At 13:13 2015-03-03, you wrote:
| Quote: | --> AeroElectric-List message posted by: Tim Olson <Tim(at)myrv10.com>
I know in my case I've done complete mixture cut-off tests
in the plane where I've stopped the engine completely,
and also flown it dry on tanks for testing, and the prop
keeps spinning so fast that you may even perceive that
the engine is still making power.
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Been there, done that too . . . many times. I've
been given to understand that many power plants
with geared props may not windmill that way.
Never had a chance to fly one and find out.
I wonder if the geared engines on the C-175
would have demonstrated this characteristic.
But as you mentioned, going through the
necessary re-start processes at altitude
is generally not a series of events accomplished
with great urgency. My youngest son was secretly
worried about the engine stopping during
the earliest years of our flying experiences
together. When I found out about it, I
demonstrated the physics of the matter at
altitude over southern Kansas. It got a bit quieter,
but it wasn't really clear to the neophyte
that the engine wasn't producing power. So
in addition to throttle closed, mixture
at cutoff, I turned off the mags and handed
him the keys.
We then did some maneuvers and took note of
our rate of descent. Told him I could finish
my Coke before things would get really
tense.
IGN . . . ON.
Throttle . . . FULL.
Mixture . . . Advance.
Sho' 'nuf, all things were right with
the universe.
Perception is everything. But perception
based on bad physics is at best useless;
at worst dangerous. I worry about the human
factors of adding starter buttons to the
stick for the purpose of expediting
a start while airborne. If you're at
so low an altitude that time is truly
of the essence . . . then perhaps
one is better advised to concentrate on
pilotage as opposed to systems analysis
and recovery.
The #1 cause of engine stoppage is fuel
exhaustion. The probability of having
an engine failure in departure configuration
is very low . . . the likelihood of 'fixing'
the problem is poor while distracting
the pilot from more pressing concerns
. . . like walking away from the landing.
Bob . . .
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