Viscount724
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Is Wake Turbulence Common At Cruising Altitudes?

Sun Jul 22, 2012 8:38 pm

Noted the following item in the Transport Canada daily occurrence reports for June 29 involving a 727-200 freighter. How frequently is wake turbulence encountered at cruising altitudes?

Kelowna Flightcraft Boeing 727-200 (C-GQKF) operating as KFA 272 was en route from Edmonton, AB to Hamilton, ON at FL 350. While in the vicinity of Winnipeg, MB the flight passed a Boeing 747 travelling in the opposite direction at 1000 feet above. Shortly afterward C-GQKF began to shake from what was described as extreme wake turbulence. The PIC then disengaged the autopilot and the aircraft rolled to the right and descended approximately 300 feet, at which point the PIC regained control and climbed back to the assigned altitude. The flight then continued to Hamilton without further incident.

[Edited 2012-07-22 14:03:17]
 
IAHFLYR
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RE: Is Wake Turbulence Common At Cruising Altitudes?

Sun Jul 22, 2012 9:40 pm

I believe there is some turbulence caused by the wing in flight. If you ever get a few thousand feet below while following the same flight track from another aircraft a few miles ahead you will experience the wake from the other airplane. If can be quite annoying if both are at the same speed for hours, a nice little washboard affect from what I remember.
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tdscanuck
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RE: Is Wake Turbulence Common At Cruising Altitudes?

Sun Jul 22, 2012 11:17 pm

Quoting Viscount724 (Thread starter):
How frequently is wake turbulence encountered at cruising altitudes?

Not that often. All airliners produce trailing vortices all the time but, thanks to "big sky theory" and ATC tending to keep aircraft apart you don't actually hit another guy's wake very often.

Sometimes, when doing odd maneuvers like a 360-degree descending turn (not something commercial service does very often) you can run into your own wake.

Quoting IAHFLYR (Reply 1):
I believe there is some turbulence caused by the wing in flight.

Yes. The wake is always there (it's a byproduct of keeping you up in the sky). It's just not that big relative to the huge volume of sky so it's fairly easy to miss.

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26point2
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RE: Is Wake Turbulence Common At Cruising Altitudes?

Mon Jul 23, 2012 2:23 pm

The advent of super accurate GPS navigation and RVSM 1000' vertical separation has increased enroute wake turbulence encounters.

On oceanic tracks where there is no radar separation and several aircraft may be flying along an identical track at different altitudes it is permitted to fly an offset track up to 2nm without an ATC clearance to avoid the wake. An upwind offset is preferred.

In the old days when we used VLF Omega for oceanic nav everyone was slightly off course and staggered to one side or another which helped to avoid the wake. Not any more.
 
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tb727
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RE: Is Wake Turbulence Common At Cruising Altitudes?

Tue Jul 24, 2012 1:03 am

Wake has a distinct feel to it to when you hit it at altitude compared to turbulence. It's usually easier to tell when it's mostly smooth and you hit the path at more of a perpendicular angle. Just a quick dip and bump then back to nothing.

[Edited 2012-07-23 18:05:08]
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sshd
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RE: Is Wake Turbulence Common At Cruising Altitudes?

Tue Jul 24, 2012 10:10 am

Quoting tdscanuck (Reply 2):
Sometimes, when doing odd maneuvers like a 360-degree descending turn (not something commercial service does very often) you can run into your own wake.

Experienced that myself two days ago with a C172  . Quite fun to be honest!
 
deaphen
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RE: Is Wake Turbulence Common At Cruising Altitudes?

Tue Jul 24, 2012 10:28 am

Had a very interesting incident last year, we were flying from BKK to DEL on a CX 343 and on the way, all of a sudden the aircraft encountered moderate turbulence and a strong jolt was felt. I must admit it was a bit scary, after which the Captain came on the PA and mentioned that the jolt was caused by a 747 crossing us 1000 above after which the wake "fell down on us".

It was rather interesting.
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vikkyvik
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RE: Is Wake Turbulence Common At Cruising Altitudes?

Tue Jul 24, 2012 10:16 pm

Quoting deaphen (Reply 6):
I must admit it was a bit scary, after which the Captain came on the PA and mentioned that the jolt was caused by a 747 crossing us 1000 above after which the wake "fell down on us".

That's generally what wake turbulence will do. The vortices are each caught in the downwash of the other vortex. So the vortex from the left wingtip is pushing down on the vortex from the right wingtip, and vice versa.

Traveling across wake turbulence shouldn't be as big a deal, as you'll be across it before you know you hit it. In the report posted by the OP, since the 747 was traveling directly opposite the 727, the 727 was probably caught in the wake for a much longer period of time, as it (the wake) descended behind the 747.

I don't think I'll ever get tired of going to the In'n'Out by LAX, and hearing the whiplash sound of the vortices a few seconds after an airplane passes.
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