Wing tip vortices a la pushing tin...

co-joe · Post by **co-joe** » Sun Oct 15, 2006 2:05 pm

Okay so this morning over a nice cup of mocachino I get talking to this guy and he has no idea what I do for a living. Conversation goes this way and that, and he starts recounting a story of one time he was in the Cook Islands back in the early nineties.

He claims that he and a friend had a condo right by the airport and they used to go sit next to the threshold and watch the 747 come and go every day on it's way to New Zeland with fruits and such.

So one day he claims the they got the bright idea after a few beverages to go stand on the threshold as the 47 takes off towards them. He claims that the end result is that they were lifted clean off their feet and thrown through the air like rag dolls.

Now he thinks he's had an encounter with jet blast, or that he's nearly been sucked into a jet engine and counts himself lucky. I try to explain the phenomenon known as wake turbulence which he has a hard time believing. Now his story seems plausible to me for some reason.

So first I ask him if he's ever seen the movie Pushing Tin with Billy Bob Thornton to which he says with a perfectly straight face, "no why?".

So I'm almost inclined to believe this guy and this leads me to my question:

Have any of you ever actually heard of this happening in real life?

Can anybody prove that it's actually happened by video or pictures?

CJ

pokaroo · Post by **pokaroo** » Sun Oct 15, 2006 2:21 pm

this what you're looking for??

http://video.google.com/videoplay?docid ... 0267082274

2low · Post by **2low** » Sun Oct 15, 2006 2:26 pm

check out these poor plane spotters.

http://video.google.com/videoplay?docid ... 3682552533

grimey · Post by **grimey** » Sun Oct 15, 2006 2:29 pm

http://video.google.com/videoplay?docid ... 8013139574

Hard to tell if he just put the camera down, or got thrown...

wingspan · Post by **wingspan** » Sun Oct 15, 2006 2:35 pm

toolow_flaps wrote:check out these poor plane spotters.

http://video.google.com/videoplay?docid ... 3682552533

LMAO at the people on the beach!

grimey · Post by **grimey** » Sun Oct 15, 2006 2:41 pm

http://www.youtube.com/watch?v=SGhiWXKGwvk

Watch the ground beside the runway.

co-joe · Post by **co-joe** » Sun Oct 15, 2006 3:07 pm

grimey wrote:http://video.google.com/videoplay?docid ... 8013139574

Hard to tell if he just put the camera down, or got thrown...

It does look like the camara underwent something violent in nature.

Thos are funny videos!

co-joe · Post by **co-joe** » Sun Oct 15, 2006 9:11 pm

So I know jet blast can move significant amounts of beach goers and unsuspecting trucks, but the story goes he was at the rotation end of the runway. Is this plausible that he got tossed into the air like a leaf?

Nark · Post by **Nark** » Sun Oct 15, 2006 10:38 pm

I'm famous.

Grimey:

I took that video earlier this summer.

I was thrown about 40 feet or so, then got sand blasted from dust and what not.

If you look at my posting history you'll see it a few months back.

cheers.

C-FART · Post by **C-FART** » Tue Oct 17, 2006 11:30 pm

the clips demonstrate that this is certainly possible. I imagine from basic airmanship that the 'best' place to experience the effects of wake turbulence/wingtip vorteces is to be at the exact point of takoff along the runway ie when the main wheels are 1cm off the ground...you get the benefit of the wings having to carrying the entire weight of the aircraft and the proximity to the ground so there is no dispersion of the turbulence.
my two cents anyway
dc

InTheGame · Post by **InTheGame** » Wed Oct 18, 2006 8:54 am

Totally, I think we should definately get someone out there to try it right away...uh ....but I am buisy I can't sorry ...

Hedley · Post by **Hedley** » Wed Oct 18, 2006 9:32 am

'best' place to experience the effects of wake turbulence/wingtip vorteces is ... when the main wheels are 1cm off the ground

Nope. Induced drag (and wingtip vortices) are going to reduced when in ground effect, because of the reduced outward-spanwise flow of air underneath the wings.

I love accelerating in ground effect, both upright and inverted - it's great when you've got some AOA that you want to get rid of.

It's also another reason I love flying in close wingtip (line abreast) formation aerobatics - the induced drag of the inner wings of all aircraft is decreased at high AOA. Combined with the angular geometry effects, line abreast kicks ass compared to echelon. But again, any Transport Canada Inspector could have told you that.

Too much paper, not enough physics.

. . · Post by **. .** » Wed Oct 18, 2006 10:39 am

I personally would think that it's jetblast doing all of what's been discribed. I can't believe that the vorticies would be strong enough.

Cat Driver · Post by **Cat Driver** » Wed Oct 18, 2006 10:46 am

Many moons ago the tower in Vancouver let me hold at the yellow line about half way down 08 and watch the Concorde take off.

The concorde was in high alfa and almost airborne as it passed my position.

I was in a C150 and the turbulence was only strong enough to make the airplane shake a bit.

Cat

balls · Post by **balls** » Wed Oct 18, 2006 4:52 pm

endless wrote:I personally would think that it's jetblast doing all of what's been discribed. I can't believe that the vorticies would be strong enough.

Vortices are a function of wing loading. Takeoff, there are no significant vortices until rotaion.

Flying an approach heavy, slow, clean (or little flap vs more) will make significant vortices because of the wing load.

There's a video on YouTube about trying to blow a car off the runway. Maybe that's been linked here. I didn't check. Anyway, the result with less than TOGA is impressive.

Pete · Post by **Pete** » Wed Oct 18, 2006 5:07 pm

I remember coming into ppl groundschool one day and just as i sat down the teacher was playing a video. Every class hed have some vid playing before it started. This one was of a frickin 172 or some small Cessna and you could actually see the vortices on take off. Has anyone else seen that? Back then I was way too shy to ask about it....but if anyone has a link to it, or knows what Im talking about that would be amazing. Id love to see it again.

Cat Driver · Post by **Cat Driver** » Wed Oct 18, 2006 5:23 pm

The very best way to see wing tip vortices is looking back at your spray pattern as you pull up and start the turn on a calm morning when you are flying a Stearman spraying a tobacco field.

....... · Post by **.......** » Wed Oct 18, 2006 5:52 pm

co-joe wrote: He claims that the end result is that they were lifted clean off their feet and thrown through the air like rag dolls.?

Thinking back at last's week take-off from London Gatwick behind a B767 (I fly an A310) and the way we were rocked when we flew through its wake, I have no problem imagining a 170-180 pound guy being seriously ''sucked off'' his feet like said...

Now, anyone brave enough to provide some actual unfactored video proof??? Well, not me!

Also, if you ever happen to be in YYZ on Carlingview drive when anything heavier than an A320 flies over you on approach to 24R, you might just catch a glimpse of the sound and effect of vortex.

balls · Post by **balls** » Wed Oct 18, 2006 5:55 pm

Cat Driver wrote:The very best way to see wing tip vortices is looking back at your spray pattern as you pull up and start the turn on a calm morning when you are flying a Stearman spraying a tobacco field.

OR, look at the water on approach to the 08's in YVR, and see the vortices settling onto the bay. You can see them on a humid morning too, on landing or takeoff. You'll often see the mist form on the wing as it loads up on rotation, or from the wingtips or the flap tips on approach in a high humidity day.

Chances are you can outclimb a heavy on departure, but you'll be on a similiar glide path on approach unless you specifically avoid the GS.

Lurch · Post by **Lurch** » Wed Oct 18, 2006 7:17 pm

C-FART wrote:the clips demonstrate that this is certainly possible. I imagine from basic airmanship that the 'best' place to experience the effects of wake turbulence/wingtip vorteces is to be at the exact point of takoff along the runway ie when the main wheels are 1cm off the ground...you get the benefit of the wings having to carrying the entire weight of the aircraft and the proximity to the ground so there is no dispersion of the turbulence.
my two cents anyway
dc

This is on the PSTAR and since they ask these questions on every TC test you will take.

Wake Turbulance is most pernounced when you are

Heavy: need to produce more lift to stay Airbourne
Slow: Need to increase you AoA (not going to discuss Newton)
Clean: Flaps help brake up the vorticies
Not in ground effect: The ground doesn't allow the vorticies to develope thus reducing induced drag

Hope this helps DC

Lurch

flyinhigh · Post by **flyinhigh** » Thu Oct 19, 2006 6:56 am

Cat Driver wrote:
I was in a C150 and the turbulence was only strong enough to make the airplane shake a bit.

Cat

Well I was flying in a C-152 with an ex girlfriend during training and was behind the A320, I. mmm we was rocked pretty good, not to sure it was wake turbulence but I say it was

niss · Post by **niss** » Thu Oct 19, 2006 7:20 am

http://www.berkeley.edu/news/media/rele ... /wings.AVI http://www.coe.berkeley.edu/labnotes/01 ... lence.html

C-FART · Post by **C-FART** » Thu Oct 19, 2006 11:53 pm

Okay gents what I was getting at was that the best REALISTIC place to be (standing on the ground...maybe with a camera filming it so we can all get a laugh) would be at or just after the point of take off.
Yes I know wingtip vortices are reduced while in ground effect...but I hope we aren't suggesting there is nothing at all going on directly between the wingtip and the ground (a distance of about 20 ft on a 747) when it is at 150kts and lifting into the air.

For a quick reference read (esp the part about vortices forming immediately on take off)

http://www.flywestwind.com/WTC/Pprograms/turbulance.htm

Lurch wrote:
C-FART wrote:the clips demonstrate that this is certainly possible. I imagine from basic airmanship that the 'best' place to experience the effects of wake turbulence/wingtip vorteces is to be at the exact point of takoff along the runway ie when the main wheels are 1cm off the ground...you get the benefit of the wings having to carrying the entire weight of the aircraft and the proximity to the ground so there is no dispersion of the turbulence.
my two cents anyway
dc
This is on the PSTAR and since they ask these questions on every TC test you will take.

Wake Turbulance is most pernounced when you are

Heavy: need to produce more lift to stay Airbourne
Slow: Need to increase you AoA (not going to discuss Newton)
Clean: Flaps help brake up the vorticies
Not in ground effect: The ground doesn't allow the vorticies to develope thus reducing induced drag

Hope this helps DC

Lurch

Lurch, thanks for the refresher on heavy, slow and clean. kind of remember it being on the PSTAR and perhaps ALL the other TC exams I have written.
BTW wingtip vortices are best produced from Delta wing type aircraft in the above configureation...might want to add that to your lecture notes. :p

I guess for 'optimal' effect one would have to find someone willing to fly a fully loaded concorde or maybe topped out 747 just over Vsi without flaps at an altitude equal to the wingspan of said aircraft. Good Luck!!!

FamilyGuy · Post by **FamilyGuy** » Fri Oct 20, 2006 12:33 am

It's not all takeoff or landing. You should see what wake turbulence the A380 "might" generate in cruise is. Basically a no fly zone 15nm behind and 2000' below - or so I am told. Don't know if that is approach or always...

niss · Post by **niss** » Fri Oct 20, 2006 4:58 am

FG, I think they cover that in this article where they experiment with wing tip vorticies.

http://www.coe.berkeley.edu/labnotes/01 ... lence.html

Wing tip vortices a la pushing tin...

Wing tip vortices a la pushing tin...

Re: Wing tip vortices a la pushing tin...