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Is This Wake Turbulence Or "normal" Turbulence?  
User currently offlineklemmi85 From Germany, joined Mar 2009, 210 posts, RR: 0
Posted (1 year 10 months 1 day 19 hours ago) and read 3643 times:

Hi there,
since I'm heading out in the same direction pretty soon, I did some searching around youtube and came across a flight departing from LHR with the aircraft being all smooth until after takeoff there's a rapid, violent looking and sudden jolting.

The uploader states it's wake turbulence from a departing company 777 in front of them, question is... is this true, is this really wake turbulence this flight goes through?

Because keeping in mind it seems to be an A321 I would guess that it rotates earlier than a 777, so I'd suspect it to fly over the T7 wake instead of through it, especially since wake descends downwards and doesn't gain altitude.

Can someone please clarify?

The video:
http://www.youtube.com/watch?v=O3FpB78DTjI

rgds

11 replies: All unread, jump to last
 
User currently offlineLonghornmaniac From United States of America, joined Jun 2005, 3278 posts, RR: 45
Reply 1, posted (1 year 10 months 1 day 19 hours ago) and read 3613 times:

Is it possible that the rate of climb on the heavy 777 was greater than that of the A321, so even though, the A321 got off the ground sooner, they wound up being overtaken vertically by the 777?

Not saying this is the case, and it seems unlikely a passenger would easily be able to identify regular CAT from wake turbulence, but there is certainly a scenario where it could've been.

Cheers,
Cameron


User currently offlinesprout5199 From United States of America, joined Feb 2005, 1852 posts, RR: 2
Reply 2, posted (1 year 10 months 1 day 17 hours ago) and read 3591 times:

Quoting klemmi85 (Thread starter):
Because keeping in mind it seems to be an A321 I would guess that it rotates earlier than a 777, so I'd suspect it to fly over the T7 wake instead of through it, especially since wake descends downwards and doesn't gain altitude.

But seeing the windsock,light wind right down the runway, the wake would have been blown back.

Dan in Jupiter


User currently offlineYchocky From Canada, joined Jul 2009, 171 posts, RR: 0
Reply 3, posted (1 year 10 months 1 day 17 hours ago) and read 3579 times:

The FA doing the announcement didn't even skip a beat.

User currently offlineklemmi85 From Germany, joined Mar 2009, 210 posts, RR: 0
Reply 4, posted (1 year 10 months 1 day 17 hours ago) and read 3567 times:

Quoting Longhornmaniac (Reply 1):
Is it possible that the rate of climb on the heavy 777 was greater than that of the A321, so even though, the A321 got off the ground sooner, they wound up being overtaken vertically by the 777?

Interesting thought... Around this time most of the 777 flights should go eastbound, right? So they're very likely very heavy to cover 11-14 hours of flying... what rate of climb could a 777 achieve with a reasonable TOW for such trips? I know these massive engines give a lot of thrust but can it outclimb a 321 loaded with fuel for just over an hour airtime?


User currently offlineLonghornmaniac From United States of America, joined Jun 2005, 3278 posts, RR: 45
Reply 5, posted (1 year 10 months 1 day 16 hours ago) and read 3537 times:

Quoting klemmi85 (Reply 4):
Interesting thought... Around this time most of the 777 flights should go eastbound, right? So they're very likely very heavy to cover 11-14 hours of flying... what rate of climb could a 777 achieve with a reasonable TOW for such trips? I know these massive engines give a lot of thrust but can it outclimb a 321 loaded with fuel for just over an hour airtime?

I had the same thought. Keep in mind, it's entirely possible that BA would not refuel in DUS (though if it is a RON, I'd be surprised if they didn't), which would then necessitate them carrying both legs of fuel. Also, with derated takeoffs and climbs, you never know.

There are also plenty of BA 777 flights going to the Middle East (I know BA 155 to CAI leaves in the early evening, and though this appears to be late evening given amount of light and time of year, I imagine there are others). A Middle East-bound 777 would be considerably lighter than a Far East-bound 777.

Cheers,
Cameron


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17001 posts, RR: 67
Reply 6, posted (1 year 10 months 1 day 15 hours ago) and read 3506 times:

A couple of factors speak for wake turbulence:
- Close to an airport, on what is probably a departure procedure.
- Sharp jolt and then nothing.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 7, posted (1 year 10 months 1 day 9 hours ago) and read 3429 times:

Quoting klemmi85 (Thread starter):
Because keeping in mind it seems to be an A321 I would guess that it rotates earlier than a 777, so I'd suspect it to fly over the T7 wake instead of through it, especially since wake descends downwards and doesn't gain altitude.

Keep in mind that Airbus, by default, uses overspeed takeoffs to improve climb gradient. As a result, if you don't play with anything, any Airbus will use more runway before rotating than a Boeing using its default (which is a balanced field).

Weight may not have much to do with it.

Tom.


User currently offlinestratosphere From United States of America, joined Sep 2007, 1651 posts, RR: 4
Reply 8, posted (1 year 10 months 1 day 6 hours ago) and read 3370 times:

Quoting Starlionblue (Reply 6):
A couple of factors speak for wake turbulence:
- Close to an airport, on what is probably a departure procedure.
- Sharp jolt and then nothing.

Bingo! ...I had it happen a few times right near an airport when it was smooth then a violent jolt then nothing. Two come to mind for me had a UsAir F-28 coming into CLT in a turn we were rocked so hard the overhead bins came open. Then one time coming into MSP on NW on a DC-9. I fly a lot and I can pretty much tell if it is wake or something other than that.



NWA THE TRUE EVIL EMPIRE
User currently offlineklemmi85 From Germany, joined Mar 2009, 210 posts, RR: 0
Reply 9, posted (1 year 10 months 1 day 6 hours ago) and read 3369 times:

Quoting Longhornmaniac (Reply 5):
I had the same thought. Keep in mind, it's entirely possible that BA would not refuel in DUS (though if it is a RON, I'd be surprised if they didn't), which would then necessitate them carrying both legs of fuel. Also, with derated takeoffs and climbs, you never know.

Thanks for pointing that out, didn't know they did that. Is it because of fuel prices at their home base being cheaper than in DUS for example or is this done to allow the first outbound to LHR depart as fast as possible in the morning?

Quoting tdscanuck (Reply 7):
Keep in mind that Airbus, by default, uses overspeed takeoffs to improve climb gradient. As a result, if you don't play with anything, any Airbus will use more runway before rotating than a Boeing using its default (which is a balanced field).

Interesting insight, thank you.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17001 posts, RR: 67
Reply 10, posted (1 year 10 months 1 day 1 hour ago) and read 3316 times:

Quoting klemmi85 (Reply 9):
Is it because of fuel prices at their home base being cheaper than in DUS for example or is this done to allow the first outbound to LHR depart as fast as possible in the morning?

Fueling typically takes less time than boarding so sounds like a cost thing.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offline3rdGen From Bahrain, joined Jul 2011, 235 posts, RR: 0
Reply 11, posted (1 year 9 months 4 weeks 1 day 22 hours ago) and read 3075 times:

Firstly, Don't make assumptions about the 321 Climb rate vs. the 777. The 777 wing was built for its size, the 321 wing is built for a 320. The 321 has a notoriously small wing, so much so that its approach speeds are higher than most wide bodies and it is categorized as a class D aircraft (due to approach speed), where as the Wide-Bodies are usually Class C. The 321 does not climb well and I wouldn't be surprised if a 777 would beat it up to cruise, even at high take-off weights.

Secondly, remember that Wake Turbulence doesn't remain steady it blows around in the wind. And in most cases there's some factor of head wind into the direction of an aircraft's take-off. Hence even if the 321 lifted off at a point along the runway before of the 777 it might well have flown into wake turb that was created ahead of its position but that had blown back. However, as stated this is only the case if the climb rate is worse than the preceding aircraft.


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