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Visible wingtip vortex!



 
 
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  #1  
Old October 24th 05, 06:25 PM
Bill
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Default Visible wingtip vortex!

Yesterday I was flying back from a weekend camping trip, and came up
behind my friend in his AA5. I started getting up close, and was
feeling the effect of the vortex off his right wingtip. I reached the
point that I had my ailerons deflected almost 50-60% to the right just
to stay level, when I suddenly SAW the vortex hitting my windshield!

I know if I heard this description I would say it was bull****. But I
saw it, as did my passengers. It was a tube of swirling distortion,
dropping down off his wingtip and then coming back to us. At that
point, I had rolled out of position, and was way off to his right. My
passengers all wanted to see it again, so we dropped behind and
started closing in again.

Imagine the way heatwaves createa a shimmering effect. It was the
same thing, except it was swirling instead of shimmering. We saw it
twice more, and it was a lot of work to do it. There is a VERY narrow
cone behind the wingtip in which it's visible, and it's very difficult
to stay in one position while the vortex is essentially centered on
the windshield.

We all tried to describe it in words, and the bottom line is it looked
like some strange special effect from a movie. Words like "wormhole"
were thrown around. But if I had seen this in a movie I would have
said it was bull**** and complained about directors making up crap
just for special effects.

So, I'm going to try to duplicate this at some point, and video
tape.it. The sun was in front of us, and that may have played a part,
but I'll find a way to duplicate it and get it on video.

When I do, I'll post it on my site and I'll announce it here as well.

Anyone else actually seen the wingtip vortex like I'm trying to
describe?


Bill Strahan
------------
Find a new reason to fly
www.adventurepilot.com

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  #2  
Old October 24th 05, 06:36 PM
Larry Dighera
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Default Visible wingtip vortex!

On Mon, 24 Oct 2005 12:25:15 -0500, Bill wrote in
::

It was a tube of swirling distortion,
dropping down off his wingtip and then coming back to us.


Did what you saw have any moisture component that made it more
visible?
  #3  
Old October 24th 05, 06:47 PM
Bill
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Default Visible wingtip vortex!

On Mon, 24 Oct 2005 17:36:15 GMT, Larry Dighera
wrote:

On Mon, 24 Oct 2005 12:25:15 -0500, Bill wrote in
::

It was a tube of swirling distortion,
dropping down off his wingtip and then coming back to us.


Did what you saw have any moisture component that made it more
visible?


No. We discussed this as well. This was nothing like the vortices
you see when it's humid, especially from jets on landing.

This was just a visual distortion, like what would happen if you
looked through glass that had a big dimple in it. And if you weren't
almost perfectly centered on it, it was invisible.

You could not see it from the side of the plane, nor from behind it
unless the center of the vortex was actually hitting the windshield.


Bill Strahan
------------
Find a new reason to fly
www.adventurepilot.com

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  #4  
Old October 24th 05, 06:50 PM
Jim Burns
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Default Visible wingtip vortex!

Not the wingtip vortices, but prop wash vortices. On very humid days, we
can see them swirl past the cabin of our Aztec on take off roll. I've also
seen them many times watching crop dusters take off.
Jim


  #5  
Old October 24th 05, 06:52 PM
Bill
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Default Visible wingtip vortex!

On Mon, 24 Oct 2005 12:50:20 -0500, "Jim Burns"
wrote:

Not the wingtip vortices, but prop wash vortices. On very humid days, we
can see them swirl past the cabin of our Aztec on take off roll. I've also
seen them many times watching crop dusters take off.
Jim


I've seen that as well, but it's visible from every angle. It's
essentially a small cloud created at the tip of the prop.

This was absolutely invisble unless you were centered behind it. Then
you got a distorted view of everything through it. It wasn't white,
it was clear.


Bill Strahan
------------
Find a new reason to fly
www.adventurepilot.com

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  #6  
Old October 24th 05, 07:06 PM
Jim Burns
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Default Visible wingtip vortex!

Ahhh... nope. Haven't ever seen that. Sounds like a ghost though. Spooky.

Visually identifiable compressed air held together by centrifugal force
traveling through relatively less compressed air?

Jim


  #7  
Old October 24th 05, 07:28 PM
Bill
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Default Visible wingtip vortex!

On Mon, 24 Oct 2005 13:06:38 -0500, "Jim Burns"
wrote:

Ahhh... nope. Haven't ever seen that. Sounds like a ghost though. Spooky.

Visually identifiable compressed air held together by centrifugal force
traveling through relatively less compressed air?

Jim


It WAS spooky. I don't understand how heatwaves are visible, nor do I
understand how this was visible. There were four of us in that plane,
completely dumbfounded each time we say it. It was so strange, we
were squealing like schoolgirls when we saw it the second time.

What causes distortions from heatwaves? Is it the differing density
of the air? If so, that might start to explain it.


Bill Strahan
------------
Find a new reason to fly
www.adventurepilot.com

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  #8  
Old October 24th 05, 07:35 PM
Jim Burns
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Default Visible wingtip vortex!

"Bill" wrote in message
...
What causes distortions from heatwaves? Is it the differing density
of the air? If so, that might start to explain it.
Bill Strahan


I've never heard any "official" explanation from an expert, but that's been
my understanding. Different air density bending light waves differently
than the surrounding air.

Jim



  #9  
Old October 24th 05, 07:37 PM
Ron Garret
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Default Visible wingtip vortex!

In article ,
Bill wrote:

On Mon, 24 Oct 2005 17:36:15 GMT, Larry Dighera
wrote:

On Mon, 24 Oct 2005 12:25:15 -0500, Bill wrote in
::

It was a tube of swirling distortion,
dropping down off his wingtip and then coming back to us.


Did what you saw have any moisture component that made it more
visible?


No. We discussed this as well. This was nothing like the vortices
you see when it's humid, especially from jets on landing.

This was just a visual distortion, like what would happen if you
looked through glass that had a big dimple in it. And if you weren't
almost perfectly centered on it, it was invisible.

You could not see it from the side of the plane, nor from behind it
unless the center of the vortex was actually hitting the windshield.


The index of refraction of air changes with density. Light moving
between regions of different density gets bent by the changes in the
IofR. You perceive this bending as distortion. This is what causes the
"shimmering" effect on a hot day. Light moves from hot, less dense air
near the ground to cooler, more dense air by your eyes and is refracted
at the boundary between the two air masses. The shimmering occurs
because the hot air rises, which causes the temperature and hence the
density of the air to fluctuate.

The effect is most pronounced where there is a net difference in density
between the air around the observer and the object being perceived. In
this case the light passes through only one refraction boundary. The
light is bent only once, and so it arrives at the observer at a
different angle than it left the object being observed, making it look
as if the object has moved quite a bit from where it really is. (You
can see this effect very dramatically in a fish tank.)

If the density at the object and observer are the same you can still
perceive refraction if there is more/less dense air in between, but the
effect is much less. This is because the light passes through two
refraction boundaries. The first one bends the light one way, and the
second one will (typically -- it depends on the geometry) bend it back,
so the net effect is not a change in the angle of the light but simply
an offset. The magnitude of the offset depends on how far the light
travels in the different density region. Because vortices are narrow
the refraction offset viewed from the side is too small to be perceived
by the unaided eye. But inside the vortex the light passes through only
one refraction boundary so you get an angular offset that you can
perceive. The "shimmering" is caused by small changes in the geometry
of the boundary of the vortex as the plane moves through the air.

rg
  #10  
Old October 24th 05, 07:42 PM
Gig 601XL Builder
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Default Visible wingtip vortex!


"Bill" wrote in message
...
On Mon, 24 Oct 2005 13:06:38 -0500, "Jim Burns"
wrote:

Ahhh... nope. Haven't ever seen that. Sounds like a ghost though.
Spooky.

Visually identifiable compressed air held together by centrifugal force
traveling through relatively less compressed air?

Jim


It WAS spooky. I don't understand how heatwaves are visible, nor do I
understand how this was visible. There were four of us in that plane,
completely dumbfounded each time we say it. It was so strange, we
were squealing like schoolgirls when we saw it the second time.

What causes distortions from heatwaves? Is it the differing density
of the air? If so, that might start to explain it.


Same thing, Yes.


 




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