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

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

Bob Gardner

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

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.

"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)
____________________

wrote in message


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.

Would the use of a constant speed prop change your equation?

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

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 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

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