Datum. Look at ruserious' post above yours. They were pretty much STANDARD summer midday conditions at DXB. The windshear that comes with that is the type that may destabilise an approach leading to a Go-Around but it is NOT like a microburst windshear that can bring down a large twin jet!

Yep..understood.

I'm simply suggesting the combination of adverse environmental conditions at the time of the accident (DA and Wind-shear) are VERY LIKELY to have been 'contributing factors'... As you correctly outline, other aircraft operated 'safely' just prior to the accident.. However, the ACTUAL 'recorded' winds in the immediate time window (15 seconds to 2 mins) prior to 521 crossing the runway threshold MAY have been MORE adverse (actual direction and actual strength) than the winds experienced by preceding aircraft.. Immediately following the accident, aircraft would have been limited/re-cleared to the parallel runway, which is also likely to have been subjected to LESS ADVERSE wind/turbulence conditions.. Note that Dubai Airport accommodates some of the largest aircraft maintenance facilities in the world..located immediately adjacent to the runway touchdown zone..

The airport was closed immediately following the accident.

Out of all the runways at DXB, you are probably least likely to encounter mechanical turbulence on 12L. The big hangars that you mention are down near the 30L/R end.

The 'big hangars' are immediately adjacent to where 521 came to rest...

How many Automated Weather Stations (AWS) does Dubai Airport utilise?.. Where are they actually located?.. What is the accuracy or resolution of these systems?.. What is the accuracy/resolution of what is actually reported to pilots by ATC or via ATIS etc?.. Note, the Wind Direction is LIKELY to be reported +/-5 to10 deg, wind speed +/- 2 to 5 knots, depending on the AWS hardware/software used..and the wind speed.

The wind COULD have been 100-105 deg at close to 25 knots?..

Has the airport/hangar infrastructure been wind tunnel tested, in order to ensure the preservation of safe operational margins in wind conditions such as those characteristic to flight 521?..

These are some of the things I would be keen to clarify during the investigation..

Vilas 1042
 

Global Express fulfills all the criteria of your modern automated machine and we did use automation where appropriate .

This is not always fulltime and that is where manual flying skills remain as important as ever; starting with the Wright brothers through 2 world wars into the present.

If you do not accept that basic premise then I suggest that you should keep your feet firmly on the ground.

I may be old and old - fashioned but that does not mean I am stupid !

Datum. The 'big hangars' are nowhere near the threshold or touchdown zone of 12L!

Very true but surely of insignificance since that is where the aircraft came to rest which is the opposite end to where events unfolded. The actual wind closer to the 12L threshold is bound to be of more interest.

The wind speed given in the wind check with the landing clearance was 11 knots.

immediately above the threshold of Runway 12L is the position at which the crew's problems regarding the go-around will have compounded.. From that position up to where the hull came to rest...which is the MAJORITY of the Runway, the aircraft is likely to have encountered changeable/adverse wind conditions (wind speed, wind direction, possible vertical windshear late in the approach/flare, and possibly building induced windshear)...

How accurate is the 'reported wind' (Tower - landing clearance)?.. Where is that wind measured exactly...for aircraft landing on Runway 12L?... Did the 'reported wind' of 11 knots accurately represent the wind conditions at the time 521 initiated the flare?... Was the 11 knot wind an Average (mean wind) or was it a Gust?.. What averaging (time) period was used to calculate this landing wind speed/direction; was it a 3 sec / 10 sec / 1 min / 2 min or 10 min Wind?..

I'm not suggesting that other factors where not involved..such as possible incorrect GA technique, or the possibility of an unstable approach.. However, I do hope the investigation team are examining the impact of the local conditions at the time..

Presumably you mean to prevent or reduce mechanical turbulence? -you could ask yourself if "airport/hangar infrastructure" has been wind tunnel tested for this anywhere on earth; I think the answer will be no, no-one does this. Having trees and buildings near a runway is a fact of life for pilots.

Datum, have you ever landed in Dubai, you are looking for smoking guns, where there are none. Mechanical turbulence caused by hangars, dream on

Dangerous to be so confident you are correct without fully investigating and/or understanding what I'm suggesting.. The cost associated with wind tunnel testing is NEGLIGIBLE when compared to the cost of a Boeing 777 hull loss and the other costs directly/indirectly attributable to an accident!... As with most aviation mishaps, it is likely that MULTIPLE factors will have contributed..

Has the airport/hangar infrastructure been wind tunnel tested ? Before they decide where runways and buildings should be in the next 40 years ? get real-

If 10kts to 25kts of wind ends up with a smoking hull on the RWY, then Id suggest they're ATO will be doing some explaining. However combine that with the PF's apparent lack of real flying experience and it may be a different discussion. As for the temp and QNH, seriously.. a B773 on two engines at or under MLW .... please.

Im looking forward to reading (or at least anecdotally hearing) about the cockpit gradient/CRM issues with this event!

Hangers most def create mechanical turb. But usually only to the extent of an uncomfortable ride. Would have thought being their home port they'd have considered this.

Datum, winds reported are at 10m AGL, so other than "windshear' there is no other reporting (currently) of the level of the windshear or the defining change.
When a pilot tells ATC they encountered windshear, usually as the reason for a GA, ATC broadcasts that until someone says they did not encounter windshear. In reporting winds, the 2min average based on 1 min readings is what is reported. Gusts are on a 10min average, unless the gust exceeds the average, then 5 minutes is used. I have no idea why gusts are reported this way. It should be understood that these measure the horizontal winds only, not the vertical winds, so a vertical windshear component cannot be measured.

Wind profilers show the winds aloft, providing details of the windspeed/direction (horizontally and vertically) and can be used to report exactly what the level and shear conditions are. How to use this information is under development.

As noted by several others, RW12L is about the least likely to encounter a wake. The conditions were right for a dry microburst.

In regards to structures, the low level ground turbulence is usually so scrambled, that structures contribute little, terrain has far more influence.

Dubai Airport integrated weather forecasting/reporting system:

http://radiometrics.com/data/uploads/2012/11/Dubai_AWDSS.pdf

Technical Spec for Viasala Automated Weather Sensor (AWS):

http://www.vaisala.com/en/products/windsensors/Pages/WM30.aspx

Wind should be +/- 3 deg?.. However, this is rounded to nearest 10 deg for METAR purposes and possibly for tower/approach reports to pilots.. The height of the A380 capable hangars is at least 25m..more like 30m.. Distance from runway is approx 420m..

What was the wind speed and direction (vector) at the top of those hangars, moments prior to the aircraft crossing the threshold, initiating the flare, initiating the go-around, settling on to the Runway?.. Was the wind measured at 10m, different at various positions along Runway 12L?.. The geometry of the airport suggests to me that if the wind had ANY easterly component, Runway 12L is more likely to experience mechanical turbulence associated with the maintenance infrastructure?.. The question is, how much Turbuelence/Windshear based on the direction and wind speed (momentary gust wind speed/total wind at 35m, NOT 10m...) This possibility is in addition to; the elevated DA and the vertical windshear characteristic to the airport environment at the time..

Anyone think a truthful and prompt report is likely from the UAE authorities?

I for one do not. Not in a month of Sundays.

This is a region where face-saving is more important than truth. So conjecture may as well continue.

OMDB 030900Z 11021KT 3000 BLDU NSC 49/07 Q0993 WS ALL RWY TEMPO 35015KT 1500

The wind could have been rounded from 105 deg up to 110 deg for METAR or Tower Reported Wind.. The accuracy of the wind sensor is approximately +/- 3-5 deg.. This means the wind direction could have been in the range 100-102 deg..

The total wind speed (including momentary gust) at 10m may have been closer to 25 knots +/- error.. However, at 35m, the height of the hangar roof, the wind speed is likely to have been higher than 25 knots..

I seem to remember RJTT (Tokyo Haneda) 34L and mechanical turbulence from close proximity hangars, but these are much closer to the runway touchdown area than the location of the DXB hangars to 12L.

Datum, the standard for aviation winds is 10m, winds are standard at this location for takeoff and braking performance. The winds are usually measured at only one location per airport. What can be worse if they are measured at multiple locations and then averaged together.

Cup anemometers only measure the horizontal component of the wind. When it is gusting, the cups tend to overspeed and keep running past the gust, hence the 10 minute average.

As you are alluding to, winds do not always blow completely horizontally, affected by structures and terrain. The Ekman spiral is typically used in aviation (procedure design) to estimate winds aloft and the direction rotation at altitude due to the influence of terrain drag and the Coriolis effect.
Wind seldom is completely horizontal, following a Kelvin Helmholtz type pattern
http://www.brockmann-consult.de/Clou...k-w-system.gif
so it is important that the vertical wind component be measured due to uplift/downdraft components that are typical in winds.

http://i67.tinypic.com/x2p92w.jpg

Even at my backwater port we get the threshold wind, on Final, from ATC. If the other winds on the airport are majorly different, ATC will tell us. I severely doubt Dubai would not have a similar system. This "averaged" wind concept is probably a furphy.

Datum

-3/5 degrees and a few knots will make little difference. It was a 777 that was involved and not a light single.

DXB has cup anemometers and the exact location of each of them can be found in the UAE AIP if you wish to look.

Landing at Philadelphia one day, the wind was given at threshold, mid-point, and far end of the runway. All were different, the far end being 180 deg. removed from the headwind at the threshold. A 727 awaiting clearance was given permission for immediate take-off, no delay. No, said the 727 pilot, I'm going to stay here and watch this 747 land. Barsteward.

It might be that the way many major airports are measuring wind is NO LONGER GOOD ENOUGH..especially given their propensity to also develop the associated land up to the legal limits imposed by the Obstacle Limitation Surface (OLS). These limits may not be suitable when it comes to certain combination of wind speed/direction (vector) and the proposed or existing location of large (width, height and length) buildings..

I believe many major airports globally, are using far more sophisticated AWS than those which utilise cup anemometers. I think you'll find that Dubai, and many FAA Major airports use more modern measuring equipment. See the internet links in my previous posts.

10 Minute Mean Winds have VERY LIMITED application to Flying Operations.. Note, that most aircraft crosswind limits refer to total crosswind (inclusive of GUST).. Gust Wind or a 1 Minute Maximum Sustained Wind would be far more applicable..

Aviation and Non-Aviation Infrastructure can significantly impact on an airport's wind environment, particularly when structures are adjacent to operational runways.. Note that visibility is measured at three different sections of the Runway for Low Vis Operations. It may transpire that the Aviation community should be measuring wind at multiple points around an airport..including on the roof of very large hangars or terminal buildings?..

Building Induced Turbulence and Windshear becomes a more significant issue when aircraft are limited to certain Runways due to performance issues (thrust, TODR, weight, PCN to name a few)...which may not be ideal given the prevailing wind at the time, regardless of whether the wind is a Mean Wind, Gust Wind, Total Wind...and/or whether it is measured at 10m or 35m..

All I'm suggesting is that IMHO, this issue should be EXAMINED IN DETAIL by the accident investigation team..

Further, all pilots need to educate themselves about building induced turbulence/windshear and should remain vigilant as to its presence in certain adverse wind conditions..

in regards to PHL:

Here is the map of the data sources used for the MET at PHL, of which, there is but a single MET location for wind measurement...how the estimate the winds at each end is generated, well...

http://i67.tinypic.com/2hqtq9v.jpg

http://i65.tinypic.com/2lu8m6a.jpg

http://i68.tinypic.com/xlma9s.jpg

EDIT:
Your link was a Vaisala WM30, a cup anemometer. I believe you will find that most still use the cup anemometer system. While the FAA wanted replacement back in 2010, I think you will find most have not.

Bloggs..I stand corrected on YMML

They have added a second anemometer north of RW9/27 How these gives one TCH info is a bit of a stretch..

MLW1 and MLW2 shown

http://i68.tinypic.com/23kx0kx.jpg

Is it safe to assume pros/public being prepped to accept WS as the prime reason for this operational incident? Contemplating between intense technical discussion or being brainwashed.

Wind tunnel testing is actually quite common for architects. A brief look into research in this area shows Effect of terrain and building structures on the airflow in an airport | SpringerLink a study at Hong Kong.

If airports do not do this then they should. A long time ago in a previous existence when doing talkdown controllers learned where there would be significant changes in wind in certain conditions over some ground features.

Before airports make use of their real estate to put up hangars in addition to the impact on the obstacle clearance surface and thus DAs, they should really confirm that winds would not result in rotor streaming or concentrated straight line winds from or between the buildings across the runways and their approach paths.

I am pretty sure the UAE authorities monitor this forum and would be prepared to bet that since the general trend recently has been to talk about wind and even wind shear, the final report will include some phrases verbatim from this forum. After all, it could not possibly be a lack of training, complacency or pilot error for relying entirely on the AUTO button could it..?

The only times I saw the hands of the anemometer dials rock steady was when there was a dead calm. Despite the damping mechanisms they generally fluctuated about mean indications of direction and strength (speed) which is what you passed on to pilots. There were rules about rapidly notifying defined changes. Thinking back ( a long way) I believe our indicators were driven mechanically direct from anemometer on tower roof few feet above. 75ft agl. Pilots are better served today but wind and rain hasnt changed much.

One of my tasks as a P Met O was airfield inspection re. siting and maintenance of instruments. I can vouch that on RAF airfields there was great care taken to site the anemometer well within the known rules, and many anemos were extremely well sited. Civil UK was a very different matter. One was so bad that I refused to sign off the inspection as satisfactory.

Whatever and however "wind" is measured: vertical motion, many sites, gusts, algorithms ........, I find it difficult to understand what use ever finer detail will be to a landing captain. I think the answer may be education rather than instrumentation.

The wind it bloweth where it listeth, and no observation[s] are infallible predictors.

langleybaston,

Far more can be done...

More accurate measuring equipment has been developed, tested and is now available Commercial Off the Shelf (COTS)..

The cost of new AWS/ASOS is NEGLIGIBLE when compared to the cost of a B777 hull loss..

If Airport Operators can afford to build large terminals, hangars, car parks and office buildings they surely can afford the costs associated with fully investigating and monitoring the impact of this infrastructure on the ongoing safety of flying operations..

Further, airports don't just cater for HEAVY jets.. The impact of development needs to be examined with regard to ALL AIRCRAFT that use, or are forecast to use an airfield..including light aircraft, medium aircraft and helicopters..

What if you had the details of the winds for final? If you are on final with a slight tailwind or crosswind, and at 120m, the winds shift to a strong headwind? Would you find that information useful if it could be provided? (even strong headwind aloft to mild headwind at 100m overspeed)
I noted at locations known for windshear that there were several GA in a row, but on second attempt, all landed. That was due to the situational awareness, so if you had that information to begin with, would there be less chance of a GA?

Other than simply windshear from ATC, would not the details and flight level of the windshear be of value?

Same for DEP, what if surface winds are calm, but at 100m you have a strong headwind, ATC says windshear, but what are you set for, calm winds? Would that not help?

It already is. The current wind is displayed on the ND. If ATC says the threshold wind is something different, then guess what... you're going to get a wind change.

The ND shows the wind component you are flying through as a component of the flightpath based on several factors. The ATC winds may not have anything to do with the windshear, nor the actual level. Nothing, not even the aircraft, shows the vertical wind component.
If this was so easy, why are there so many go arounds and FOQA busts?

What does the ND say when you are on the ground, ready to depart?

Flight deck displays of ‘instant’ wind velocity based upon on board computations are now quite accurate when instant variation is not required. This is especially true when the aircraft is away from the ground, but their usefulness for assisting the execution of a safe touchdown, landing roll or take off roll is often very limited, both for practical and computational reasons. Updating of on-board readouts of wind velocity depends on the system which generates them. FMS wind is the most accurate, because it is based upon changes of GPS or DME/DME position, but it may only be re-calculated every 30 seconds. Wind Velocity based upon an INS is often calculated as many as 10 times per second but the result is less precise. The net effect is that neither have real value near or on the ground.

Where's the white suit? I think I'm going nuts!

The current wind is not displayed on the ND.

Next time you are flying along, gently add a little rudder input.

If you aren't that brave, try it in the simulator.

Yep, confirmed. I am nuts. Let me try a bit of rudder therapy...

Capn Bloggs, please, please, can I book you for my next flight? Reading some posters here I think I might be going nuts as well.

Bloggs, You of course, know more than anyone else.

Please explain how the ac determines the winds? Crosswinds?

Airspeed, groundspeed and rudder? What happens in a turn? The vertical windspeed component with uplift and downdraft? Your aircraft and skills are amazing!

Please enlighten all of us. All of these GA from windshear would be eliminated!

A bit curious on your Perth destination now that you know that have one weather station and a bunch of windsocks, that they provide threshold wind measurements? (and change them when an ac cannot rotate?) You are so good that you get the winds and check the windsocks on final?

Sorry, Nut Flight 001 has already departed with Capn Bloggs and FO Megan at the controls. Windsocks of the world unite! :D