Is this interpretation right? There are parallel runways, and the plane departing on the runway on the right turned left, into the path of the plane departing parallel on the left?

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t0mas88 a day ago | parent | next [-]

Yes that's what happened. And this is a very common mistake.

A bit simplified, but what happens is that each flight is assigned a departure procedure during startup. That procedure is runway specific and designed to keep traffic clear of other runways so they can have traffic departing from multiple runways at the same time.

Imagine a runway on the left and one on the right, the left runway departure procedures would have an early left turn and the right runway departure procedures would be straight ahead until some altitude and then a right turn.

Now if you depart from the right runway but accidentally select the departure procedure for the left runway, the instruments (and autopilot) would indicate a left turn at about 500ft, right into the path of traffic from the left runway.

This mistake is common when for example a plane is first assigned the left runway and then during taxi changes to the right runway. Or the preflight paperwork includes the left runway departure procedure, but the actual assignment from ATC is the right runway (this was a source of incidents in Amsterdam for a while with some airlines)

If you're really interested, read this incident report via Google Translate, it describes exactly how this type of incident happens: https://www.lvnl.nl/voorvallen/20220415-verlies-van-afstand-...

	▲	ageek123 a day ago \| parent [-]
		This is exactly why the takeoff clearances say “RNAV xxx, cleared for takeoff”. It’s a last confirmation, right before takeoff, of which departure procedure to use.

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SilverElfin a day ago | parent | prev [-]

Yes exactly. They were within 1000 yards of each other and less than 5 seconds from colliding according to some videos analyzing the GPS data. If you listen to the ATC chat, the American Airlines pilot noticed the other plane going the wrong way himself and made a proactive change to avoid collision without waiting for ATC. Although the traffic controllers did notice and quickly gave out new directions, it may have been too late if the pilot didn’t act.

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goblin89 a day ago | parent [-]

Edit: They were handed off to departures before tower’s traffic warning. The near-collision occurred in the middle of tower-departures handoff. Tower was warning them of traffic in hopes they were still on the frequency but they probably weren’t, and they noticed traffic just before they contacted departures.

On ATC side, maybe departures could have been more proactive and warn AA of traffic together with tower. On AA side, maybe they could have been listening to tower for a while as they are tuning in to departures (there were 10–20 seconds where AA was not listening to tower anymore and did not come in on departures yet). Seems hard to blame either of them in particular.

Original comment as is:

If the video is to be believed, the tower did tell American right away (at 1:36 in the video, way before any visible corrections by either plane were made) that there is traffic and to stop the climb. It’s unclear whether American paid attention to tower, because seconds later they came in on another frequency saying they have traffic in sight. When asked afterwards whether tower gave them a heads-up they denied it.

Of course, ITA paid even less attention, considering how they were the original cause of this all and how for 30 seconds they ignored ATC’s request to turn right immediately (issued at about the same time that AA was warned about traffic).

This doesn’t contradict that what AA did was proactive and possibly life-saving, but I have a suspicion that the initial deviation by ITA could have been benign if both crews paid their full attention to comms: what if ITA started to turn 270 immediately as they are told to (while continuing to climb up from 1500), and American simply stopped their climb at 1500? I am not 100% confident.

That said, I would also agree ATC could have been more proactive, harder on ITA (instead of just telling them to turn again 30 seconds later). Presumably they are strapped for resources right now.

(There could be errors in the above in case the chart and different radio communication tracks in the video are out of sync with each other, which is possible.)

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jvanderbot a day ago | parent | next [-]

They said they had traffic in sight in response. As in "yes I see them". I believe their avoidance maneuver was a climb change.

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goblin89 a day ago | parent [-]

If “in response” means replying back to tower on tower’s frequency, then no. After the lady on tower frequency told them about traffic (twice), they came in on departures frequency (it was a fresh contact, they started with “good afternoon, American 4 with you”) and said they have traffic in sight.

Edited after I rewatched the video:

1. Tower handed them off to departures.

2. They said bye and stopped listening to tower.

3. ITA veered left.

4. Tower noticed it and warned them, hoping they are still listening.

5. They were evidently not listening to tower anymore, and did not contact departures yet, when they noticed traffic themselves.

6. They greeted departures saying they see traffic, and veered left.

Later at 2:45 American said tower didn’t give them a heads-up. The fact that departures asked them about it could mean that departures thought they were still listening to tower.

Pretty sure the pilots have a second radio and could be listening to both departures and tower during handoff, but it’s unclear whether that’s routine. If they did it, they would have heard tower’s original warning.

> I believe their avoidance maneuver was a climb change.

According to the chart in the video, AA veered to the left. This maneuver started around 1:51 in the video, which is at least 10 seconds after tower warned them of traffic and instructed to stop the climb for the first time around 1:38.

I don’t know if they stopped the climb around 1:38. If we know for sure that they stopped the climb around 1:38 when tower told them so, then there is a good chance they were indeed still listening to tower and heard the traffic warning. If that’s the case, maybe they thought that stopping the climb 10 seconds earlier was insufficient (and tower was wrong about it).

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rmccue a day ago | parent [-]

Note that VASAviation's visualisations are not always 100% synched with ATC radio recordings, and the radio usually has gaps removed. It's a useful overview to see the tracks, but take the video's timing with a grain of salt.

	▲	goblin89 18 hours ago \| parent [-]
		I mentioned that in my original comment. Unless it is out of sync by tens of seconds, however, it is clear that they were handed off to departures and were neither responding nor even listening to tower.

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gosub100 a day ago | parent | prev [-]

One theory in the comments was that ITA loaded the wrong departure in their computer and just flew it without noticing that they were on the wrong side of the airport and/or ATC's prior instructions contradicted the electronic plan.

	▲	sdh9 a day ago \| parent [-]
		They had the correct SID, but the wrong runway.