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Another super jumbo shook A380 in Mum

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People inside an Airbus A380 feel very safe because they know they are inside the world's largest commercial airliner. But now, they would do well to be wary of another aircraft of the same size. The severe turbulence caused on a Mumbai-bound Singapore Airlines (SIA) Airbus A380 that left 22 people on board injured on Saturday night may have been caused by another A380. Preliminary investigation by the directorate general of civil aviation (DGCA) has indicated that another super jumbo may… (epaperbeta.timesofindia.com) More...

Er.A.K. Mittal
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akayemm
Er.A.K. Mittal 1
I request for views from experts of fluid mechanics and aerodynamics. The basics as I remember say that the wake will be in vortex form. Implying the reduction in force as you travel away from the eye (vertex) and the range of force or the diameter of the vortex or the wake will keep increasing with distance , both following square law . So simply fixing vertical separation without any correlation with horizontal separation seems utterly out of place . So theoretically, if two aircrafts cross each other without any separation will not suffer from turbulence from the wake . Because there will be none !
More over accepting that in the current example the wake is effective upto 985 ft., fixing a limit of 1000 ft. separation seems illogical, a clearance of just 15 ft., unless some of you pilots can claim that instruments are so good and precise that you can safely fly within accuracy of inches ! I hope guys from insurance companies are also reading with interest.
Do fill me in please.
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preacher1
preacher1 1
I personally think they are grasping at straws or something easy. I don't think 15' will make that much difference, and these have been flying for several years and no other happenings.
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akayemm
Er.A.K. Mittal 1
So the investigators are deliberately approaching the problem wrongly for ulterior reasons or they are just idiots or what ?
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preacher1
preacher1 1
IDK; I think it was something right there up front and made the job easier for the moment. Definitely not their final answer.
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akayemm
Er.A.K. Mittal 1
ThanX. I'll stop at this. But true professionals are not expected to use words that can be misconstrued much less making a clear cut incomplete technical statement like that the a/c suffered turbulence due to wake of another a/c !
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preacher1
preacher1 1
10-4, they did say MAY but you are correct. Better to have not said anything at all until sure, of which they aren't.
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akayemm
Er.A.K. Mittal 1
Sorry for dragging. Even the sentences using words like "may" should be correct on the touchstone of science.
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preacher1
preacher1 1
They should not be used at all. They carry much more weight than normal coning from such a body
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joelwiley
joel wiley 1
Interesting.
Maybe the ATC data will be forthcoming.
300 meters (985 ft) for the A380, a cursory google search didn't come up with a number for B747. If one was10 ft high, the other 10 ft low that would put them in range.

1000 ft vertical separation has been around for years. Has that been revisited with the advent of the A380? Should it?
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akayemm
Er.A.K. Mittal 1
You'll agree that the size of the wake and its force will be proportional to volume of the aircraft and the combined thrust of the engines. Elementary , I hope .
If that be so, the rest will be a natural fall-out . Or corollaries to the main theorem !
Whether authorities visit/revisit limits or not , that's a different ball game, IMHO.
Right ?
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akayemm
Er.A.K. Mittal 1
The vertical difference limit vis-a-vis actual gap gives an interesting food for thought . As stated, the specified limit is 1000 ft. and the actual gap was 985 ft., short by just 15 ft. ! IMHO , either 1000 ft. limit is too less or the meter reading of 985 ft. was wrong.
Or was there some thing else which my layman's eye could not see ?
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preacher1
preacher1 2
Well the gap was close but what is puzzling to me is that these things have been in the air several years and this is only the first time happening. Either it has been overlooked or this is entirely wrong. Good to see you back on.
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akayemm
Er.A.K. Mittal 1
ThanX. Pleasure is all mine.
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