Feathering an engine

"vaughn" wrote in message
...

"Tim" wrote in message
m...


So you are saying if I loose power at high altitude in a fixed pitch prop
aircraft, like a Skyhawk, I will have less drag if I stop the prop, as
opposed to letting it windmill?

Yes, but with a fixed pitch prop you may or may not be able to stop the
prop by slowing down to a near stall. Once stopped, it may or may not
stay stopped at best glide speed. It would depend on the pitch of your
prop, the compression of your engine, your plane's best glide speed, the
quality of the pilot's speed control, and the phase of the moon.

Vaughn

Are you high?
Have you actually done it?
I can assure you, all aspects of it are much easier than you imply.

"Tim" wrote in message
m...

"vaughn" wrote in message
...

"Tim" wrote in message
m...


So you are saying if I loose power at high altitude in a fixed pitch
prop aircraft, like a Skyhawk, I will have less drag if I stop the prop,
as opposed to letting it windmill?

Yes, but with a fixed pitch prop you may or may not be able to stop the
prop by slowing down to a near stall. Once stopped, it may or may not
stay stopped at best glide speed. It would depend on the pitch of your
prop, the compression of your engine, your plane's best glide speed, the
quality of the pilot's speed control, and the phase of the moon.

Vaughn

Are you high?
Have you actually done it?
I can assure you, all aspects of it are much easier than you imply.



Vaughn is absolutely correct in stating that many aircraft with fixed-pitch
props will windmill all the way in, as you would have to be near or below
its rated stall speed for it to stop. Depends on the particular aircraft in
question :-)

"John E. Carty" wrote in message
...


"Tim" wrote in message
m...

"vaughn" wrote in message
...

"Tim" wrote in message
m...


So you are saying if I loose power at high altitude in a fixed pitch
prop aircraft, like a Skyhawk, I will have less drag if I stop the
prop, as opposed to letting it windmill?

Yes, but with a fixed pitch prop you may or may not be able to stop the
prop by slowing down to a near stall. Once stopped, it may or may not
stay stopped at best glide speed. It would depend on the pitch of your
prop, the compression of your engine, your plane's best glide speed, the
quality of the pilot's speed control, and the phase of the moon.

Vaughn

Are you high?
Have you actually done it?
I can assure you, all aspects of it are much easier than you imply.



Vaughn is absolutely correct in stating that many aircraft with
fixed-pitch props will windmill all the way in, as you would have to be
near or below its rated stall speed for it to stop. Depends on the
particular aircraft in question :-)

Perhaps, but that wasn't the question, and what does the phase of the moon
have to do with anything but starting a ****ing contest?

There is no doubt in my mind that all the singles I have flown will windmill
all the way in. I'm not aware of any direct drive, piston singles that
won't. You in fact have to be very, very slow to stop the prop, but it's not
difficult do to do. But even at airspeeds well above max glide, I have never
had a stopped prop restart against compression without at least bumping the
starter.

The point was how much do you gain by stopping a fixed pitch prop, as
opposed to letting it wind mill. I was taught many years ago, that if you
experience a power failure at high altitude, stopping the prop could mean
the difference in reaching a distant landing area. Some of the posts in this
thread suggests it makes no difference. I thought it might be to everyone's
benefit to clarify.

In article ,
"Tim" wrote:

The point was how much do you gain by stopping a fixed pitch prop, as
opposed to letting it wind mill.

A lot.

You can actually do this experiment in a plane with a variable-pitch
prop. Idle the engine, and play with the prop control. I did this
years ago in a 182RG during dead stick landing drills. The difference
in glide performance between the two extreme prop settings was quite
dramatic, almost like having an extra set of very fast acting flaps.

There's also the conservation of energy argument. If the engine is
turning, the energy to overcome friction and compression has to come
from somewhere.

rg

In article ,
Ron Garret wrote:

There's also the conservation of energy argument. If the engine is
turning, the energy to overcome friction and compression has to come
from somewhere.

I don't think this works. In the non-spinning case, you're dissipating
all that energy into the air, and there's no real limit as to how much
that could be. Now, it would seem that the conservation-of-energy
argument gets you the right answer, but IMO not for the right reasons.

--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon

On May 7, 8:22*am, Mike Ash wrote:
In article ,
*Ron Garret wrote:

There's also the conservation of energy argument. *If the engine is
turning, the energy to overcome friction and compression has to come
from somewhere.

I don't think this works. In the non-spinning case, you're dissipating
all that energy into the air, and there's no real limit as to how much
that could be. Now, it would seem that the conservation-of-energy
argument gets you the right answer, but IMO not for the right reasons.

--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon

I couldn't see, from those charts, that the spinning prop
developed a LOT more drag, like the flat plate some here claimed it
would be. A flat plate the diameter of the prop disc would be about
four times the flat-plate equivalent of the aircraft's profile, I
think, and would steepen the glide to some awesome angle.
I'm going to have to go up and do it again. Many years ago I
stopped the prop on a 150 and found that the glide was a hair steeper
for a given airspeed. The prop stopped, reluctantly, near the stall,
and diving the airplane to Vne would not restart it.
How many others here have actually tried it, besides me?

Dan

wrote in message
...

I couldn't see, from those charts, that the spinning prop
developed a LOT more drag, like the flat plate some here claimed it
would be. A flat plate the diameter of the prop disc would be about
four times the flat-plate equivalent of the aircraft's profile, I
think, and would steepen the glide to some awesome angle.
I'm going to have to go up and do it again. Many years ago I
stopped the prop on a 150 and found that the glide was a hair steeper
for a given airspeed. The prop stopped, reluctantly, near the stall,
and diving the airplane to Vne would not restart it.
How many others here have actually tried it, besides me?

Dan

----------------------------------------------------------------------------------------

It was demonstrated to me during flight training many years ago. I did it a
few times later after I got my license just for fun, and an opportunity to
hear the airframe with no engine noise.

I never had a problem stopping the prop, but probably never exceed 100 kts
while gliding. In no situation did a prop ever attempt to restart it's self.
However, just a bump of the starter would send it wind milling again, even
with the mixture still closed.

In article ,
Mike Ash wrote:

In article ,
Ron Garret wrote:

There's also the conservation of energy argument. If the engine is
turning, the energy to overcome friction and compression has to come
from somewhere.

I don't think this works. In the non-spinning case, you're dissipating
all that energy into the air, and there's no real limit as to how much
that could be. Now, it would seem that the conservation-of-energy
argument gets you the right answer, but IMO not for the right reasons.

I'll grant you it's not a slam-dunk argument, but it sure seems
plausible that it takes a lot more energy to turn a dead engine than it
does to move a stopped prop through the air at ~100 knots.

rg

On May 8, 1:36 am, Ron Garret wrote:

I'll grant you it's not a slam-dunk argument, but it sure seems
plausible that it takes a lot more energy to turn a dead engine than it
does to move a stopped prop through the air at ~100 knots.

rg

It would seem so, but a stopped prop still swallows energy. The
turbulence behind it translates into heating of the air. If you have a
sensitive thermometer in a beaker of water, and stir that water, its
temperature will rise.

Dan

Ron Garret wrote in news:rNOSPAMon-
:

In article ,
"Tim" wrote:

The point was how much do you gain by stopping a fixed pitch prop, as
opposed to letting it wind mill.

A lot.

You can actually do this experiment in a plane with a variable-pitch
prop. Idle the engine, and play with the prop control. I did this
years ago in a 182RG during dead stick landing drills. The difference
in glide performance between the two extreme prop settings was quite
dramatic, almost like having an extra set of very fast acting flaps.

There's also the conservation of energy argument. If the engine is
turning, the energy to overcome friction and compression has to come
from somewhere.

rg

Actualy, a pro that is spinning freely, with no compression, as in one that
is attached to a snapped crank, will cause more drag than one which is
driving all the internal bits in most cases.



Bertie