HaveBlue
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Video: Wingtip Vortice Or Wind Sheer?

Sun Dec 17, 2006 3:01 am

I've watched this video a few times and was wondering if he hit a wingtip vortice from a preceding aircraft or if it was just a strong crosswind or wind sheer that he corrected for and then was overcorrecting side to side. Thoughts and opinions please.




http://keyetv.com/watercooler/local_story_348131609.html
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SlamClick
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RE: Video: Wingtip Vortice Or Wind Sheer?

Sun Dec 17, 2006 3:20 am

The video would require that I download flash - AGAIN - and I'm not going to do that until they fix flash so it doesn't require downloading every time, when there are already half a dozen instances of it on my hard drive. /rant

I'm assuming that we are talking about SeaTac and the very windy days they had?

If so, there is not much chance of a wake turbulence encounter as the wind will break it up and move any lingering fragments away very quickly.

On the other hand, SeaTac is near the top of a fairly narrow ridge between Puget Sound and the Green River valley. There are steep rises north and west and the Des Moines Creek canyon to the south all of which will cause the wind to spill and roll like a stream over rocks. Arrivals there on a day when the wind is out of the southwest can be downright sporty.
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3DPlanes
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RE: Video: Wingtip Vortice Or Wind Sheer?

Sun Dec 17, 2006 5:58 am

Looks like gusting crosswinds, combined with PIO. Notice that the plane rocks back and forth several times, getting worse each time until they abort.

I wake vortex event would (normally) be a rapid rolling event, either left or right, followed (hopefully) by a correction back to wings level.
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Starlionblue
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RE: Video: Wingtip Vortice Or Wind Sheer?

Sun Dec 17, 2006 7:09 am

Quoting HaveBlue (Thread starter):
wind sheer

Sheer is for stockings.
Shear is for wind.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
HaveBlue
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RE: Video: Wingtip Vortice Or Wind Sheer?

Sun Dec 17, 2006 1:32 pm

Fair enough Slam, I don't blame ya. Thanks for the description of the environment there, I'm not familiar with it.

3D I know how the vortices effect the plane to an extent, I've been in a DC-9 when we hit wake turbulence from a heavy (this confirmed by the pilots of said DC-9). What made me think it wasn't just crosswind was that the approach up til that exact point seemed very stable, didn't look like he was crabbing/slipping or fighting it at all, then all of the sudden the rapid right roll, quickly corrected (or overcorrected) by left roll, and yes the PIO seemed very apparent. I thought maybe he hit the left wing wake turbelence, corrected to the right but too much, then tried to counter with left, etc. You can watch the spoilers quickly go left, right, left, right before he aborts and goes around. If it was a crosswind condition it seems he would have had some correction in there to start, not just a sudden and rapid 90' crosswind affecting the plane.

Starlion, my English error duly noted.  Smile
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speedracer1407
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RE: Video: Wingtip Vortice Or Wind Sheer?

Sun Dec 17, 2006 5:34 pm

Quoting 3DPlanes (Reply 2):

I wake vortex event would (normally) be a rapid rolling event, either left or right, followed (hopefully) by a correction back to wings level.

While I'm certainly no expert nor pilot, I did experience a somewhat similar situation aboard a COex ERJ 145 last year on final approach to ORD. We were probably at something like 500 feet or so, and we suddenly rolled left-right-left-right-left-right in rapid succession. It startled everyone on the plane. We didn't go around, but I'd bet money that if the same thing happened at 50 ft AGL, we would have.

Anyway, as we deplaned, nearly EVERYONE asked the pilots what it was all about, and they answered over and over again that it was wake turbulence from a 757 crossing our path at a very small angle.
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speedracer1407
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RE: Video: Wingtip Vortice Or Wind Sheer?

Sun Dec 17, 2006 5:47 pm

Wait...while my previous post made no specific assumtions about the reason behind the NWA 757's visually dramatic go around, I should probably also point out that the video shows the succcessful landing afterwards, which displayed the same seemingly dramatic left-right roll inputs--right down to the landing in which the left mains touch down DURING a roll moment.
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Starglider
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RE: Video: Wingtip Vortice Or Wind Sheer?

Mon Dec 18, 2006 7:18 am

Quoting 3DPlanes (Reply 2):
Looks like gusting crosswinds, combined with PIO.

Or maybe wake vortex from a nearby building or structure? Here at AMS there was a structure (blast wall of an engine run pad) that created vortices which affected the touchdown area of a runway. They had to lower the wall.
 
pilotpip
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RE: Video: Wingtip Vortice Or Wind Sheer?

Mon Dec 18, 2006 9:10 am

SEA has had some rediculous weather the last week or so. Another pilot forum offered this reasoning:

757s are known for getting this roll going in strong crosswinds. It has something to do with the roll spoilers being deployed. Boeing issued an SB for this and has installed vortex generators on the outer leading edge to help with this.
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3DPlanes
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RE: Video: Wingtip Vortice Or Wind Sheer?

Mon Dec 18, 2006 12:45 pm

Quoting Starglider (Reply 7):
Or maybe wake vortex from a nearby building or structure?

That occurred to me too, but I'm not familiar with SEA.

I do recall that MSP has issues with the big NW hangar blocking crosswinds and creating low-level turbulence for the two parallels - depending on where the wind is from...
"Simplicate and add lightness." - Ed Heinemann
 
Starglider
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RE: Video: Wingtip Vortice Or Wind Sheer?

Mon Dec 18, 2006 8:59 pm

Quoting 3DPlanes (Reply 9):
That occurred to me too, but I'm not familiar with SEA.

I do recall that MSP has issues with the big NW hangar blocking crosswinds and creating low-level turbulence for the two parallels - depending on where the wind is from...

A few years ago i arrived and departed SEA regularly. Can't recall anything that stood out to have such an effect on either of the parallel runways. But the only constant is change. So maybe something large enough may have been built there since?
 
Fly2HMO
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RE: Video: Wingtip Vortice Or Wind Sheer?

Tue Dec 19, 2006 9:46 am

Quoting 3DPlanes (Reply 2):
combined with PIO



Quoting HaveBlue (Reply 4):
and yes the PIO seemed very apparent

Pretty obvious PIO as noted. The landing definitely apllies to my signature Big grin

Quoting HaveBlue (Reply 4):
What made me think it wasn't just crosswind

Looked tailwind-ish to me, dont recall the average 753 approach to be that fast over the ground and not that flat either, but thats just me...
 
Starglider
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RE: Video: Wingtip Vortice Or Wind Sheer?

Wed Dec 20, 2006 5:46 am

Quoting FLY2HMO (Reply 11):
753 approach

In this case, a 752 approach. I noticed that the upset took place at exactly the same location near touch down. In the video, during both approaches, first the plane passes a double light post in the foreground relatively stable, then hits turbulence near touchdown, in both cases exactly when about to pass the tree branches in the foreground. Second time less severe but still evident.

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