Prop performance in clouds question

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

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

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

"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

On Mar 4, 2:12*am, Bertie the Bunyip wrote:

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

Bertie- Hide quoted text -

Very interesting link. Thanks

That appears to confirm the reaction of the prop in the video in that
the video is picking up the approximately 1 percent degradation of
engine performance inside the cloud through the strobing of the prop
using the values of 70F (OAT of flight in video) 29.92 70 percent or
100 percent humidity and 6000 ft altitude.

Allen

On Mar 4, 8:10 am, " wrote:
On Mar 4, 2:12 am, Bertie the Bunyip wrote:

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

Bertie- Hide quoted text -

Very interesting link. Thanks

That appears to confirm the reaction of the prop in the video in that
the video is picking up the approximately 1 percent degradation of
engine performance inside the cloud through the strobing of the prop
using the values of 70F (OAT of flight in video) 29.92 70 percent or
100 percent humidity and 6000 ft altitude.

Allen

The marginal reduction in BHP performance is offset by the marginal
increased TAS, n'est pas?

Dan

On Mar 4, 8:58*am, " wrote:

The marginal reduction in BHP performance is offset by the marginal
increased TAS, n'est pas?

Dan

Do I understand you to be saying TAS would increase after entering
IMC???

Allen

On Mar 4, 10:03 am, " wrote:
On Mar 4, 8:58 am, " wrote:

The marginal reduction in BHP performance is offset by the marginal
increased TAS, n'est pas?

Dan

Do I understand you to be saying TAS would increase after entering
IMC???

Allen

If the air density has decreased due to increased humidity (clouds),
there will be offset between to reduction in BHP efficiency and the
increased TAS (due to reduced profile drag)....


Dan

" wrote in news:77bb7a2a-6285-4bb2-
:

On Mar 4, 10:03 am, " wrote:
On Mar 4, 8:58 am, " wrote:

The marginal reduction in BHP performance is offset by the marginal
increased TAS, n'est pas?

Dan

Do I understand you to be saying TAS would increase after entering
IMC???

Allen

If the air density has decreased due to increased humidity (clouds),
there will be offset between to reduction in BHP efficiency and the
increased TAS (due to reduced profile drag)....



Maybe, but the water on your wings is going to cost you quite a lot.


Bertie