Prop performance in clouds question

Good point, but I still think that the OP is seeing an optical illusion.

Bob

wrote in message
...
Bob Gardner wrote:
I think what you are seeing is an optical illusion. The prop speed
doesn't
change because of the air it is penetrating.

It may be an optical illusion, but engine RPM for a fixed throttle/mixture
setting will most definitely change because of the air, otherwise there
would be no reason to have a mixture control.


--
Jim Pennino

Remove .spam.sux to reply.

On Mar 2, 7:08 pm, " wrote:
Only flying after today for the next month will be as a passenger as
November 1943 lima has been delivered to Batesville for the extreme
interior makeover. I asked the interior guy if he could email me some
progress pics and he said he would.

Another pilot followed me up in his piper seen here athttp://picasaweb.google.com/allenlieberman/AirplanePics/photo#5173324...

I **thought** air is less dense in a cloud, but when you watch the
prop strobing athttp://www.youtube.com/watch?v=QniPjy0gkBIyou can
see the regression of the prop strobing, and in my experiences when
the prop starts turning counter clockwise, the prop RPM is slowing
down.

We were in level flight, 6000 feet. Engine is 180 hp. I don't
remember what settings he had for the prop or engine.

Would the moisture in the cloud cause a change in the prop speed even
though we couldn't detect it via gauge or sound? Or is air inside a
cloud more dense?

What I found most fascinating is that we both left the same time, and
he only got there 2.5 minutes faster. I was 45 to a downwind when his
wheels touched down. He planned 130 knots, I planned 110 knots and
the trip was 116 NM.

This for sure verfied I don't need a high performance plane for my
kind of flying as even on my trips to Bessemer, who would really
notice 7 to 10 minutes longer flight time difference **in the full
scheme of things**.

Allen

The prop strobing clockwise does not necessarily mean the prop is
slowing down. If you've ever seen a turboprop shut down under the
artificial 60hz strobing lights of an airport apron, you'll see the
prob strobe back and forth as it gradually slows down.

On Mar 3, 11:02*am, buttman wrote:

The prop strobing clockwise does not necessarily mean the prop is
slowing down. If you've ever seen a turboprop shut down under the
artificial 60hz strobing lights of an airport apron, you'll see the
prob strobe back and forth as it gradually slows down.- Hide quoted text -

- Show quoted text -

Yeah, I figured the clockwise motion wasn't indication of it slowing
down, it was when I was IMC, that it "stopped" or started going
counter clockwise, and then when I popped out, it resumed it's
clockwise motion.

It was "hands off flying" before entering the cloud, smooth inside and
same outside and NO changes in airplane configuration insofar as prop,
mixture or throttle.

Something I can try to experiment in my Sundowner a month down the
road when it gets back in service since I only have a fixed pitch
prop.

Allen

On Mar 2, 9:08 pm, " wrote:
Only flying after today for the next month will be as a passenger as
November 1943 lima has been delivered to Batesville for the extreme
interior makeover. I asked the interior guy if he could email me some
progress pics and he said he would.

Another pilot followed me up in his piper seen here athttp://picasaweb.google.com/allenlieberman/AirplanePics/photo#5173324...

I **thought** air is less dense in a cloud, but when you watch the
prop strobing athttp://www.youtube.com/watch?v=QniPjy0gkBIyou can
see the regression of the prop strobing, and in my experiences when
the prop starts turning counter clockwise, the prop RPM is slowing
down.

We were in level flight, 6000 feet. Engine is 180 hp. I don't
remember what settings he had for the prop or engine.

Would the moisture in the cloud cause a change in the prop speed even
though we couldn't detect it via gauge or sound? Or is air inside a
cloud more dense?

What I found most fascinating is that we both left the same time, and
he only got there 2.5 minutes faster. I was 45 to a downwind when his
wheels touched down. He planned 130 knots, I planned 110 knots and
the trip was 116 NM.

This for sure verfied I don't need a high performance plane for my
kind of flying as even on my trips to Bessemer, who would really
notice 7 to 10 minutes longer flight time difference **in the full
scheme of things**.

Allen

I am not sure how you came to the conclusion that air is less dense in
the cloud than the surrounding air. Density decreases with increasing
moisture for unsaturated air, but once the air is saturated (clouds),
any excess moisture is suspended as tiny droplets, and the average
density will start to increase. Darker the cloud, the higher the
density. This is why you need an updraft to hold these clouds up. When
the density gets too large to overcome the updrafts, you get rain, and
the density returns to normal.

On Mar 4, 8:27*am, Andrew Sarangan wrote:
On Mar 2, 9:08 pm, " wrote:





Only flying after today for the next month will be as a passenger as
November 1943 lima has been delivered to Batesville for the extreme
interior makeover. *I asked the interior guy if he could email me some
progress pics and he said he would.

Another pilot followed me up in his piper seen here athttp://picasaweb.google.com/allenlieberman/AirplanePics/photo#5173324...

I **thought** air is less dense in a cloud, but when you watch the
prop strobing athttp://www.youtube.com/watch?v=QniPjy0gkBIyoucan
see the regression of the prop strobing, and in my experiences when
the prop starts turning counter clockwise, the prop RPM is slowing
down.

We were in level flight, 6000 feet. *Engine is 180 hp. *I don't
remember what settings he had for the prop or engine.

Would the moisture in the cloud cause a change in the prop speed even
though we couldn't detect it via gauge or sound? *Or is air inside a
cloud more dense?

What I found most fascinating is that we both left the same time, and
he only got there 2.5 minutes faster. *I was 45 to a downwind when his
wheels touched down. *He planned 130 knots, I planned 110 knots and
the trip was 116 NM.

This for sure verfied I don't need a high performance plane for my
kind of flying * as even on my trips to Bessemer, who would really
notice 7 to 10 minutes longer flight time difference **in the full
scheme of things**.

Allen

I am not sure how you came to the conclusion that air is less dense in
the cloud than the surrounding air. Density decreases with increasing
moisture for unsaturated air, but once the air is saturated (clouds),
any excess moisture is suspended as tiny droplets, and the average
density will start to increase. Darker the cloud, the higher the
density. This is why you need an updraft to hold these clouds up. When
the density gets too large to overcome the updrafts, you get rain, and
the density returns to normal.- Hide quoted text -

- Show quoted text -

BINGO!

Cheers

On Mar 3, 1:27*pm, Andrew Sarangan wrote:

I am not sure how you came to the conclusion that air is less dense in
the cloud than the surrounding air. Density decreases with increasing
moisture for unsaturated air, but once the air is saturated (clouds),
any excess moisture is suspended as tiny droplets, and the average
density will start to increase. Darker the cloud, the higher the
density. This is why you need an updraft to hold these clouds up. When
the density gets too large to overcome the updrafts, you get rain, and
the density returns to normal.- Hide quoted text -

While I plan to ask on a meteorological forum when I get home, play
with me a sec...

I am not talking about small clouds vs big rain making clouds. What I
am talking about is the density of the air comparing VMC to IMC at an
established level of flight.

If that cloud was "denser" then the surrounding air (as you can see in
the video, it was a sparse cloud cover), then why doesn't the cloud
sink if that parcel of air is heavier (denser) then the surrounding
air?

Winds aloft were 35 knots so surely, the updraft time was extremely
minimal and I would say none, since I didn't get any lifting feeling
in the seat of my pants in penetrating that volkswagon size puffy.

When I googled the topic, it talked mainly of stratiform clouds, and
that layer being less dense below the cloud deck, which I already
understand the higher you go, the less dense the air. This is
probably where I got my initial impressions that the air in clouds is
less dense.

Allen

On Mar 3, 2:20*pm, " wrote:

When I googled the topic, it talked mainly of stratiform clouds, and
that layer being less dense below the cloud deck, which I already
understand the higher you go, the less dense the air. *This is
probably where I got my initial impressions that the air in clouds is
less dense.

Allen

To clarify, the above should say MORE dense below the stratiform cloud
deck!

Allen

On Mar 3, 3:20 pm, " wrote:
On Mar 3, 1:27 pm, Andrew Sarangan wrote:

I am not sure how you came to the conclusion that air is less dense in
the cloud than the surrounding air. Density decreases with increasing
moisture for unsaturated air, but once the air is saturated (clouds),
any excess moisture is suspended as tiny droplets, and the average
density will start to increase. Darker the cloud, the higher the
density. This is why you need an updraft to hold these clouds up. When
the density gets too large to overcome the updrafts, you get rain, and
the density returns to normal.- Hide quoted text -

While I plan to ask on a meteorological forum when I get home, play
with me a sec...

I am not talking about small clouds vs big rain making clouds. What I
am talking about is the density of the air comparing VMC to IMC at an
established level of flight.

If that cloud was "denser" then the surrounding air (as you can see in
the video, it was a sparse cloud cover), then why doesn't the cloud
sink if that parcel of air is heavier (denser) then the surrounding
air?

Good question. Let us know what the meteorologists say about this. My
thinking is that the cloud will eventually sink to the ground if left
undisturbed (think fog). But it may float for quite some time,
especially if the droplets are small. From your photo, the clouds look
white, which implies very small droplets. Think of those parachute-
like flowers that float in the spring. All they need is a tiny gust of
air, and they stay afloat for ever.





Allen

On Mar 3, 3:32*pm, Andrew Sarangan wrote:

Good question. Let us know what the meteorologists say about this. My
thinking is that the cloud will eventually sink to the ground if left
undisturbed (think fog). But it may float for quite some time,
especially if the droplets are small. From your photo, the clouds look
white, which implies very small droplets. *Think of those parachute-
like flowers that float in the spring. All they need is a tiny gust of
air, and they stay afloat for ever.

Okee dokee, this was response I received on the meteorological aspect
between the dashed lines.
--------------
All other things being equal (temperature, pressure,etc), air with
more water vapor in it is less dense than air with less water vapor in
it. Air is mostly Nitrogen (N2, roughly 78%, molecular weight 14) and
Oxygen (O2, roughly 21%, molecular weight 16), while water vapor is
H2O (molecular weight 10).

The problem is, I don't think all other things are equal when you go
from non-cloud to in-cloud. It may be within the degree of accuracy of
your instruments, but there are still some very small differences in
temperature and/or pressure.
----------------

Meteorologist also said, though not with any conviction since he is
not a mechanic by any stretch of the imagination becuase there is less
air in a cloud, that **could** reduce engine performance (he said it's
plausible, no necessarilyt the answer) which in turn could reduce the
RPM of a prop.

Allen