EK703 Near-Collision w/ HM054

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HJ1an
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EK703 Near-Collision w/ HM054

Postby HJ1an » Mon Aug 07, 2017 6:49 am



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Re: EK703 Near-Collision w/ HM054

Postby SHM » Mon Aug 07, 2017 3:06 pm

o_O

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Re: EK703 Near-Collision w/ HM054

Postby jwocky » Mon Aug 07, 2017 3:55 pm

There are like fifty open questions. For example:

- why did the ATC not notice EK703 read back wrong?
- why did EK703 not see HM054 in their TCAS? HM054 saw the Airbus ...
- why cut vertical separation so narrow at all and why not use also a horizontal separation? The Airbus is so big he would need later anyway a wider turn to get ILS at the airport.
- did the ATC not see, EK703 was descending on after crossing FL380 and why was there no reaction in time?

and later, when there was this talk about a report:
- was the ATC not aware, he was in the same boat as the EK703 pilot? He accepted the wrong read-back

Maybe I am a bit naive here, but when I ATC, for example at a festival, I use basically in each direction two lanes, one incoming, one outgoing. That's it. So even if someone is getting an altitude wrong or had AP problems, over- or undershoots, he can never get in the traffic from the other direction.
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Re: EK703 Near-Collision w/ HM054

Postby HJ1an » Tue Aug 08, 2017 12:09 am

This is what my fear is about increasing air traffic. Those implementing new systems (and including the planemakers) seem happily content with addition of more planes into the crowded skies and even DECREASING air separation, because, yay!, tech allows us to do so now. Which may be true. But all it takes is one visibility poor weather, one sleeping controller, one ACAS turned off by maintenance crew, one pilot mouth not connecting to the brain (let's face it, we have all been there. Say one word when you meant another) to have a open invitation to a major disaster.

Sure, safety issue and accidents have decreased over the years, but to me that's the calm before the storm. It's like Malaysia Airlines. They, (and their [non-existent] Air Force) were way too content, and then they suddenly had 2 major accidents 3 months apart that at least one of them could be totally preventable, while the other could have at least prevented a complete mystery.

Also, that part about the planemakers, of course they are happily implementing these systems / advocating decreasing separation, I will try not to be cynical but they benefit monetarily, of course.

That looked too close. Also it seems weird that they'd turn right when left makes more sense, but I am guessing here there is simply no time to choose. Just turn it to survive.

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Re: EK703 Near-Collision w/ HM054

Postby Omega » Tue Aug 08, 2017 2:45 am

- why did the ATC not notice EK703 read back wrong?

Major hearback error by the controller.

- why did EK703 not see HM054 in their TCAS? HM054 saw the Airbus ...

They both saw each other on TCAS. But as you can hear in the background during one of the transmissions, there was only a TCAS TA (Traffic Advisory); it never got close enough to the point where there was an RA (Resolution Advisory). Seychelles had visual contact with Emirates so they took action. On the other hand, Emirates most likely didn't have visual on Seychelles so they couldn't really take immediate action without a TCAS RA.

- why cut vertical separation so narrow at all and why not use also a horizontal separation? The Airbus is so big he would need later anyway a wider turn to get ILS at the airport.
- did the ATC not see, EK703 was descending on after crossing FL380 and why was there no reaction in time?

This is a completely non-radar environment over the Indian Ocean. That's why the controller only relies on pilot reports in the audio recording. Mauritius island is quite isolated, with the next closest VOR being 120 miles away. So there is only one airway going directly northbound (UR400F). Both aircraft have to be on that airway as there is not any other choice. A vector is impossible in a non-radar environment. It appears that they put aircraft northbound on UR400F at odd altitudes and southbound aircraft at even altitudes.

and later, when there was this talk about a report:
- was the ATC not aware, he was in the same boat as the EK703 pilot? He accepted the wrong read-back

The controller is clearly at fault here. But he tried to blame Emirates instead of taking the responsibility.

That looked too close. Also it seems weird that they'd turn right when left makes more sense, but I am guessing here there is simply no time to choose. Just turn it to survive.

They turned right because that's standard to avoid head-on collisions. Both aircraft should turn right, you don't want to have a situation when one turns right and the other turns left.
Last edited by Omega on Tue Aug 08, 2017 8:16 am, edited 1 time in total.

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Re: EK703 Near-Collision w/ HM054

Postby HJ1an » Tue Aug 08, 2017 4:02 am

Omega wrote:They turned right because that's standard to avoid head-on collisions. Both aircraft should turn right, you don't want to have a situation when one turns right and the other turns left.


Aahh yes. I totally forgotten about that. Thanks for reminding me.

But in that route track, it seems like they would have to (and did) make a really hard right just to stay out of the way because a slight right would put it into an even closer path with it.

Omega wrote:They both saw each other on TCAS. But as you can hear in the background during one of the transmissions, there was only a TCAS TA (Traffic Advisory); it never got close enough to the point where there was an RA (Resolution Advisory). Seychelles had visual contact with Emirates so they took action. On the other hand, Emirates most likely didn't have visual on Seychelles so they couldn't really take immediate action without a TCAS RA.


With scale being the issue main issue we're looking at here of course, but that still seems like have TCAS a TA when they are heading towards each other at those closing speeds, the margins are kinda narrow don't you think.

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Re: EK703 Near-Collision w/ HM054

Postby Omega » Tue Aug 08, 2017 6:32 am

With scale being the issue main issue we're looking at here of course, but that still seems like have TCAS a TA when they are heading towards each other at those closing speeds, the margins are kinda narrow don't you think.

The longitudinal margins are indeed narrow, but we have to remember that Emirates was on a descent through Seychelles' altitude. A TCAS RA can only be triggered if the TCAS projects that the other aircraft will come to a dangerously close proximity. Now if Emirates was maybe 300 feet lower than Seychelles on a constant descent (downward arrow displayed) an RA will not really trigger as there is no danger. I may be wrong though, as I don't know the exact algorithms used by a TCAS, nor the actual longitudinal and vertical separation of these aircraft.

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Re: EK703 Near-Collision w/ HM054

Postby jwocky » Fri Aug 11, 2017 6:52 pm

Why is that total no-radar there? The airbus went a moment later down to FL60 for going to the approahc lane, so they were not more than 150nm out, if that much, and they have transponders there and secondary radar on the Seychelles which would easily give them the latitude over more than 200nm. As you said, it's ocean there, not many mountains in the way.
And yes, it's only one traffic way there ... which is exactly what I criticize. The Seychelles are a major tourist destination, means mostly big planes. Those big birds don't do evasion as fast as a little Beechcraft.
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