Visible wingtip vortex!

[Bill]

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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[Larry Dighera]

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?

[Bill]

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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[Jim Burns]

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

[Bill]

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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[Jim Burns]

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

[Bill]

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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[Jim Burns]

"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

[Ron Garret]

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

[Gig 601XL Builder]

"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.

[Jim Burns]

See Bill? I was right! It was a ghost! :)
Jim

[Bill]

On Mon, 24 Oct 2005 13:46:08 -0500, "Jim Burns"
> wrote:

>See Bill? I was right! It was a ghost! :)
>Jim
>

Yeah, that sounds just as reasonable, just like those spirits that
mock me by yelling back at me. For some reason, those spirits are
always around certain canyons and caves.

I'll get this ghost on video before the end of the year, hopefully.

I just couldn't believe I had never heard of this being visible,
especially with the number of people who fly formation for recreation.

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

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[.Blueskies.]

"Bill" > wrote in message ...
> 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
> ------------


Where was the sun relative to your view? There is an effect called a "schlieren visualization" that describes why we see
mirages and the like, sort of like seeing the heat rise off a candle. I once watched a shock wave dance around on the
nacelle of a DC-10. The sun was the "coherent light source" low on the horizon. It was pretty strange to see. I have
also read that NASA and DARPA have used high power optics from the ground to observe airflow around an aircraft at high
altitudes.

Dan D.

[Bill]

On Mon, 24 Oct 2005 18:56:44 GMT, ".Blueskies."
> wrote:

>
>"Bill" > wrote in message ...
>> 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
>> ------------
>
>
>Where was the sun relative to your view? There is an effect called a "schlieren visualization" that describes why we see
>mirages and the like, sort of like seeing the heat rise off a candle. I once watched a shock wave dance around on the
>nacelle of a DC-10. The sun was the "coherent light source" low on the horizon. It was pretty strange to see. I have
>also read that NASA and DARPA have used high power optics from the ground to observe airflow around an aircraft at high
>altitudes.
>
>Dan D.
>

The sun was ahead, and above the wing. Not so bad that it was
blinding us though. If I had to guess....draw a line from us as
observer to the wingtip. The sun was 20-30 degrees higher than that.
It definitely wasn't close to head on.

FWIW, this was about 5:30 yesterday, Paris, Tx area.

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

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[Tony Goetz]

A great example of this is when the space shuttle lands, particularly at
Edwards (at KSC it tends to be humid so water vapor forms in the vortices
and masks the refraction). I've noticed it a few times and it is mainly
visible in video pointed right down the runway. Super high wing loading, I
would guess. I searched for a while but could only come up with one decent
video showing the phenomena. Pictures don't really demonstrate it. This
video is in quicktime *.mov format, so my apologies if you can't view it.

http://www.fotosearch.com/comp/FIL/FIL101/EV0116.mov

The physics of it are just those of compressible flow. Change in density
leads to change in the index of refraction of the gas. Visible, as someone
else said, via the Schlieren optical system often used in
transonic/supersonic wind tunnels. I've seen such a setup in action at the
supersonic tunnel at my school. Pretty cool stuff.

http://www.ae.su.oz.au/aero/super2d/ssflow3.html
http://web.mit.edu/edgerton/people/vandiver/schlieren.html


-Tony Goetz
Rocket scientist in training.

[Ron Garret]

In article >,
Bill > wrote:

> 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.

Start here:

http://en.wikipedia.org/wiki/Refraction

rg

[Tony Goetz]

Morgans wrote
> > A great example of this is when the space shuttle lands, particularly at
> > Edwards (at KSC it tends to be humid so water vapor forms in the
vortices
> > and masks the refraction). I've noticed it a few times and it is mainly
> > visible in video pointed right down the runway. Super high wing loading,
I
> > would guess.
>
> I had always thought that was mainly due to the fact that the air coming
off
> the bottom of the wing was hot as **** from re-entry. Perhaps some of
both?
> --
> Jim in NC


The effect only seems to be visible where the wingtip vortices would be, so
my guess would be that it's at least mostly due to them. As for the tiles
being as hot as ****, I don't think it's unusual for the ground support guys
and even the crew to wander around the shuttle not long after landing, even
touching the tiles, so I doubt they're still too hot. The tiles work by
storing the energy of re-entry within the material without raising their
temperatures too much. At the aerodynamic surface of the tiles the
temperature does get up into the thousands of degrees due to the shock
heating, but by the time the shuttle touches down they've likely cooled to
somewhat just cooler than ****.

But those are just my thoughts and possible unreliable memories of photos
and video. I hope someone corrects me if I'm wrong.


-Tony "I'm not an aerospace engineer yet but I play one on TV" Goetz

[Morgans]

"Bill" > wrote

> 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.

You are the first I have ever heard describe this. Interesting. I would
think that there was a little moisture component along with the density and
diffraction, but perhaps not.

They say the late NASCAR race car driver, Dale Earnhart, could see "the
draft." His success at the highest speed tracks, where the draft was the
most important, would seem to make you think that he had something extra
working for him. Your account makes me give more credence to that legend,
now. Thanks for posting.
--
Jim in NC

[Morgans]

"Tony Goetz" > wrote

> A great example of this is when the space shuttle lands, particularly at
> Edwards (at KSC it tends to be humid so water vapor forms in the vortices
> and masks the refraction). I've noticed it a few times and it is mainly
> visible in video pointed right down the runway. Super high wing loading, I
> would guess.

I had always thought that was mainly due to the fact that the air coming off
the bottom of the wing was hot as **** from re-entry. Perhaps some of both?
--
Jim in NC

[Bob Fry]

>>>>> "bill" == bill > writes:

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

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

This brings up a question. Why don't we experience the same
distortion all the time behind our single-engine props? Surely that
distortion would be more than what you saw, yet I've never noticed
anything like it. Maybe the distorted tube of air is too short (a few
feet) whereas your wingtip tube was many feet?

[Morgans]

"Tony Goetz" > wrote

> As for the tiles
> being as hot as ****, I don't think it's unusual for the ground support
guys
> and even the crew to wander around the shuttle not long after landing,
even
> touching the tiles, so I doubt they're still too hot.

> by the time the shuttle touches down they've likely cooled to
> somewhat just cooler than ****.

<chuckle> You are most likely right. I remember seeing people pick up a
cube of tile material, just a few seconds after they came out of a furnace,
glowing red hot. Amazing stuff, for sure.

--
Jim in NC

[Bill]

On Mon, 24 Oct 2005 21:34:59 GMT, "Tony Goetz" >
wrote:

>A great example of this is when the space shuttle lands, particularly at
>Edwards (at KSC it tends to be humid so water vapor forms in the vortices
>and masks the refraction). I've noticed it a few times and it is mainly
>visible in video pointed right down the runway. Super high wing loading, I
>would guess. I searched for a while but could only come up with one decent
>video showing the phenomena. Pictures don't really demonstrate it. This
>video is in quicktime *.mov format, so my apologies if you can't view it.
>
>http://www.fotosearch.com/comp/FIL/FIL101/EV0116.mov
>
>The physics of it are just those of compressible flow. Change in density
>leads to change in the index of refraction of the gas. Visible, as someone
>else said, via the Schlieren optical system often used in
>transonic/supersonic wind tunnels. I've seen such a setup in action at the
>supersonic tunnel at my school. Pretty cool stuff.
>
>http://www.ae.su.oz.au/aero/super2d/ssflow3.html
>http://web.mit.edu/edgerton/people/vandiver/schlieren.html
>
>
>-Tony Goetz
>Rocket scientist in training.
>

Yep, that's it, except the one from the AA5 was tiny. It seemed to be
no more than a 2" cone.

Notice how you can't see it at ALL until it gets down into line of
sight along the vortex. Same as my flight.

Guys, I'm gonna get video...it will be on the site. It's just amazing
looking.


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

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[Wallace Berry]

>
> Where was the sun relative to your view? There is an effect called a
> "schlieren visualization" that describes why we see
> mirages and the like, sort of like seeing the heat rise off a candle. I once
> watched a shock wave dance around on the
> nacelle of a DC-10. The sun was the "coherent light source" low on the
> horizon. It was pretty strange to see. I have
> also read that NASA and DARPA have used high power optics from the ground to
> observe airflow around an aircraft at high
> altitudes.
>
> Dan D.
>
>



I once watched the shockwave on the wing of a 757 in flight for quite a
while. It was visible as a noticeable line of refraction in the air over
the wing and it cast very distinct shadows on the wing. The shadows took
the form of arcs similar to shadows cast on a stream bottom by ripples
in the water. An airline pilot friend said they used to see them on the
wings of 727's when they would get up close to their highest cruise
speed.

[.Blueskies.]

"Bill" > wrote in message ...
> On Mon, 24 Oct 2005 18:56:44 GMT, ".Blueskies."
> > wrote:
>
>
> The sun was ahead, and above the wing. Not so bad that it was
> blinding us though. If I had to guess....draw a line from us as
> observer to the wingtip. The sun was 20-30 degrees higher than that.
> It definitely wasn't close to head on.
>
> FWIW, this was about 5:30 yesterday, Paris, Tx area.
>
> Bill Strahan
> ------------
> Find a new reason to fly
> www.adventurepilot.com


Found more: http://www.nasa.gov/centers/dryden/news/FactSheets/FS-033-DFRC.html