Prop performance in clouds question

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 at
http://picasaweb.google.com/allenlie...24852142956722

I **thought** air is less dense in a cloud, but when you watch the
prop strobing at http://www.youtube.com/watch?v=QniPjy0gkBI you 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 suspect the moisture in the air made your engine deliver less power,
therefore fewer RPM...

More water per cubic foot of air = less of everything else, including
oxygen.

wrote in message
...
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 at
http://picasaweb.google.com/allenlie...24852142956722

I **thought** air is less dense in a cloud, but when you watch the
prop strobing at http://www.youtube.com/watch?v=QniPjy0gkBI you 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 would look at how the video camera compensates for the lower light
level in the cloud. If it changes its scan/shutter rate it would
cause the apparent change in relative movement of
the propeller. Also these apparent flicker/stroboscopic patterns are
not always directly related, that is the prop could be going faster
not slower as it appears. That is why car hubcaps seemed to turn
backwards in the old flicks, in spite of the vehicle obviously going
forward. What you are witnessing is the sync of the prop with the
shutter and any variation in either can cause the illusion of
movement.

D

"Doug Palmer" wrote in message


I would look at how the video camera compensates for the lower light
level in the cloud. If it changes its scan/shutter rate it would
cause the apparent change in relative movement of
the propeller. ... What you are witnessing is the sync of the prop
with the shutter and any variation in either can cause the illusion of
movement.

That's my guess, as well.

--
John T
http://sage1solutions.com/blogs/TknoFlyer
http://sage1solutions.com/products
NEW! FlyteBalance v2.0 (W&B); FlyteLog v2.0 (Logbook)
____________________

On Mar 3, 9:56*am, "John T" wrote:
"Doug Palmer" wrote in message





I would look at how the video camera compensates for the lower light
level in the cloud. *If it changes its scan/shutter rate it would
cause the apparent change in relative movement of
the propeller. *... What you are witnessing is the sync of the prop
with the shutter and any variation in either can cause the illusion of
movement.

That's my guess, as well.

--
John Thttp://sage1solutions.com/blogs/TknoFlyerhttp://sage1solutions.com/products
NEW! *FlyteBalance v2.0 (W&B); FlyteLog v2.0 (Logbook)
____________________

I am using a Kodak Easy Share camera. Does that adjust based on what
it "sees"?

I just put it on Movie and point and shoot, thus me being intrigued
figuring it was the airplane and and not the camera end.

Unless of course if the frame rate can change based on what the camera
sees being "so automatic"?

I sure don't know myself, but pretty coincidental seeing the strobe
change in VMC vs IMC.

Allen

wrote in message


I am using a Kodak Easy Share camera. Does that adjust based on what
it "sees"?

Cameras typically use a combination of shutter speed, aperture and exposure
to maintain the "best" picture (as defined by the software). I haven't
researched your camera, though I suspect it manipulates all three based on
the video I've seen on your channel. I know for certain your shutter speeds
are way different from mine based on the prop filtering.

Unless of course if the frame rate can change based on what the camera
sees being "so automatic"?

Possible, though I doubt actual frame rate is changing (different from
shutter speed).

I sure don't know myself, but pretty coincidental seeing the strobe
change in VMC vs IMC.

I don't doubt a small change in prop speed as I've seen similar changes in
my own prop "strobe," but I'd put it more to general atmospheric (or, more
likely, attitude changes) rather than specific to clouds as I've seen
similar changes well outside clouds on "severe clear" days.

Try this: Take video during a flight on a clear VMC day. Maintain level
flight as absolutely as you can, then enter climbs and descents. See what
that does to your prop strobe. I suspect even slight attitude changes will
show different strobe patterns without touching engine or prop controls.

--
John T
http://sage1solutions.com/blogs/TknoFlyer
http://sage1solutions.com/products
NEW! FlyteBalance v2.0 (W&B); FlyteLog v2.0 (Logbook)
____________________

On Mar 2, 8:37*pm, "Kyle Boatright" wrote:
I suspect the moisture in the air made your engine deliver less power,
therefore fewer RPM...

More water per cubic foot of air = less of everything else, including
oxygen.


So, on that volkswagon / SUV parcel size chunk of air, would the air
be less dense? I am not quite sure I understand what you mean above,
but what you describe above, I perceive you saying more dense as the
prop would have to work harder to slice through moisture laden air.

Everything I have read so thus so far, deals with the air in general
going up, is less dense, but nothing within a "benign" fair weather
cumulus cloud. Air below a stratus cloud is more dense then the
stratus cloud itself, and above the cloud is even less dense.

I think I will post to a weather forum and see if they can answer the
meteorological portion of that question.

Allen

wrote in message
...
On Mar 2, 8:37 pm, "Kyle Boatright" wrote:
I suspect the moisture in the air made your engine deliver less power,
therefore fewer RPM...

More water per cubic foot of air = less of everything else, including
oxygen.


So, on that volkswagon / SUV parcel size chunk of air, would the air
be less dense? I am not quite sure I understand what you mean above,
but what you describe above, I perceive you saying more dense as the
prop would have to work harder to slice through moisture laden air.

Everything I have read so thus so far, deals with the air in general
going up, is less dense, but nothing within a "benign" fair weather
cumulus cloud. Air below a stratus cloud is more dense then the
stratus cloud itself, and above the cloud is even less dense.

I think I will post to a weather forum and see if they can answer the
meteorological portion of that question.

Allen

The air density doesn't change, but the amount of oxygen per cubic foot
does. Imagine a one cubic foot in size. It is full of red balls
(nitrogen), white balls(oxygen), and green balls (CO2). It won't hold
another ball without removing something. Now, you have to add a bunch of
black balls (H2O). Which means you have to take out some red, white, and
green ones to make space. Now your 1 cubic foot box holds less nitrogen,
oxygen, and CO2. This is essentially what happens when the humidity rises.
What it means to a combustion engine is that the engine won't produce as
much power, because there is less oxygen per cubic foot (or whatever) of
air.

KB

On Mar 3, 6:15*pm, "Kyle Boatright" wrote:

The air density doesn't change, but the amount of oxygen per cubic foot
does. *Imagine a one cubic foot in size. *It is full of red balls
(nitrogen), white balls(oxygen), and green balls (CO2). *It won't hold
another ball without removing something. *Now, you have to add a bunch of
black balls (H2O). *Which means you have to take out some red, white, and
green ones to make space. *Now your 1 cubic foot box holds less nitrogen,
oxygen, and CO2. *This is essentially what happens when the humidity rises.
What it means to a combustion engine is that the engine won't produce as
much power, because there is less oxygen per cubic foot (or whatever) of
air.

Actually the above just **may** help support what I am thinking but in
an opposite sense..

The balls you describe above are not the same size, therefore if you
remove some of the bigger balls and replace them with smaller balls,
wouldn't that make the air "denser"

Conversly, if you take out the little balls and replace them with
bigger balls, there is more space between the balls making it less
denser.

I figure if the visible was the "bigger balls" in that parcel of air,
as compared to the surrounding air outside the IMC, then the air
inside that cloud would be less dense verifying what I have been
reading?

Does this make any sense?

It does make sense that there would be less air, thus reducing ening
power, which would change the strobing of the prop once entering IMC,
and after leaving it, that power would resume since the visible
moisture now is replaced with air.

Allen

"Kyle Boatright" wrote in
:


wrote in message
news:99678464-7bae-4911-931b-4b5bd798fc75
@n58g2000hsf.googlegroups.com.
.. On Mar 2, 8:37 pm, "Kyle Boatright"
wrote:
I suspect the moisture in the air made your engine deliver less
power, therefore fewer RPM...

More water per cubic foot of air = less of everything else,
including oxygen.


So, on that volkswagon / SUV parcel size chunk of air, would the air
be less dense? I am not quite sure I understand what you mean above,
but what you describe above, I perceive you saying more dense as the
prop would have to work harder to slice through moisture laden air.

Everything I have read so thus so far, deals with the air in general
going up, is less dense, but nothing within a "benign" fair weather
cumulus cloud. Air below a stratus cloud is more dense then the
stratus cloud itself, and above the cloud is even less dense.

I think I will post to a weather forum and see if they can answer the
meteorological portion of that question.

Allen

The air density doesn't change, but the amount of oxygen per cubic
foot does. Imagine a one cubic foot in size. It is full of red balls
(nitrogen), white balls(oxygen), and green balls (CO2). It won't hold
another ball without removing something. Now, you have to add a bunch
of black balls (H2O). Which means you have to take out some red,
white, and green ones to make space. Now your 1 cubic foot box holds
less nitrogen, oxygen, and CO2. This is essentially what happens when
the humidity rises. What it means to a combustion engine is that the
engine won't produce as much power, because there is less oxygen per
cubic foot (or whatever) of air.

http://www.csgnetwork.com/relhumhpcalc.html



Bertie