A note to ATM's when dealing with Russian Aircraft...

[Dinger]

nasty tragedy, sure. I can't blame the controller too much.  I'd rather suggest the culpability of:

A) The company that allowed one human on duty. Even on a quiet night, there's no failsafe.
B) The company that had their collision warning systems and telephones offline. (well the one controller was on the phone to an airport or something).  The one controller was isolated from any other controller out there.
C) The privatized ATC system in Europe which features tiny centers like the one oin Zurich.

And yeah, TCAS is designed to override ATC. This TCAS  RA was coordinated -- two boxes were operational, one said dive, the other said climb. The DHL jet didn't have to state it was in TCAS descent (though I think it did) and the ATC guy didn't have to acknowledge it. If the box tells the pilot to go one way, and he goes the other, bad things ensue.

Someone can correct me on the details here, but TCAS advisories come out about thirty seconds before a possible collision. ATC radars don't update fast enough for the controller to have much that's useful to say.
There are many times when it's better to trust a human voice than a mahcine. this isn't one of them.

[Boroda]

Originally posted by Toad
Nobody "makes" the Captain do anything once he's in the air. The Pilot-in-Command is in command. He can exercise his emergency authority at anytime. They can question is judgement after the fact but they cannot question his right and responsibility to act as he deems best while in the air.

The Captain ignored his TCAS advisory. I know of NO airline that has a policy of disregarding TCAS advisories in order to comply with ATC instructions.

Sorry, guys but this one falls squarely on the Captain for disregarding TCAS.

Toad, I am not an expert, and just repeat what media said here. OTOH - Estel is a retired pilot, and I think he explained what really happened.

I'd really like to see you guys discussing this issue. I know we have many airline pilots here, maybe they can speak? AFAIK Estel has all nessesary data on the accident.

[Dinger]

Eerr.... to rephrase that:

TCAS is a fail-safe system. When it issues an RA, it's because the previous method of collision avoidance (ATC) has failed (or you're operating in a very tight spot, which is not the case at FL 330). When a failsafe system triggers, it has overriding authority over the system that has just failed.

If ATC says "UP" and the system designed to work when ATC screws up says "DOWN", you go down.

true, the pilot's error wasn't the only thing that went wrong that night. There are scores of problems this scenario reveals, such as how our ultraprecise navigation systems put all aircraft at exactly the same altitude and right down the middle of the jet routes, the sheer stupidity of having a center like the one at Zurich, the second controller being (as permitted by company policy) nowhere near his post, or the fact that centers are so small you can have only one guy manning them.  But unfortunately, the only error that's not sanctioned by current aviation policy is that of the pilot.

[Estel]

Originally posted by Toad
Nobody "makes" the Captain do anything once he's in the air. The Pilot-in-Command is in command. He can exercise his emergency authority at anytime. They can question is judgement after the fact but they cannot question his right and responsibility to act as he deems best while in the air.

Yes. Exactly. But you forgot one thing. Captain can disregard any ATC if he think that it can affect safety. Is it true? Yes. But here we see: 1. TA on Tupolev. 2. ATC - Descend to FL350. Crossing traffic 60 degrees. 3. Descend was began, because for this moment (TA Alert and ATC up to time) there was conflict, but not dangerouse situation. 4. If Tupolev's crew could hear that DHL is going down, they never descend. So, they didn't hear it. They were sure that DHL is levelling. 5. RA Alert. Worse words in cabin: Were is that ****ing plane? 2nd pilot: I see nothing.... He (ATC) said down..... ****. He is speaking Climb (about TCAS). And at this moment, the chief officer, not the captain said: "****, descend! He (ATC) said descend." 6. In same moment DHL and Tupolev's crew see their planes....

For that moment - TA Alert, Captain was free to deal. It wasn't RA.  And he agreed with ATC. But when RA happened, it was too late. With additional pressing from "Checking officer" wich said - descend.

The Captain ignored his TCAS advisory. I know of NO airline that has a policy of disregarding TCAS advisories in order to comply with ATC instructions.

Sorry, guys but this one falls squarely on the Captain for disregarding TCAS.

TA is not _must_do_ advisory. It's only advisory. Only RA you must execute. RA was on descend path. They were very short of time. About 15-20 seconds. It's too low to level such plane as Tupolev.

I'll try to give you more explained answer, but later.

[Dinger]

4. doesn't make sense.
They didn't have to hear DHL was going down. Once they received the (coordinated) RA to climb, they would have known DHL received a RA to descend.

5. is the error. Two aircraft, thanks to modern avionics, are on _exactly_ the same altitude.  They both dive at collision avoidance descent rates. 15 seconds may not be enough time to pitch the nose over, but at 900 kph for each degree of change in descent you get 50 meters of vertical separation twelve seconds later.


And it's not 15 seconds, but more like 40

http://www.bfu-web.de/berichte/02_ax001est.pdf

21:34:49, the Tu154 was instructed to descend.
21:34:56, TCAS in both A/C issues a RA (it's not only coordinated; both A/C had identical TCAS hardware).
At the same time as the TCAS sounded, the Tu154 began its descent.
At the same time as the TCAS sounded, the 757 began its descent
21:35:19 the TCAS in the 757 issues its second RA ("Increase Descent"
21:35:24 the TCAS in the Tu154 issues its second RA ("Increase Climb")
21:35:32 the two aircraft collide.

[Toad]

What Dinger said. 40 seconds is PLENTY of time to reverse a descent into a climb, especially when the DHL is correctly continuing its own descent.

TA's are advisory. That's what TA means; Traffic ADVISORY. It means "heads up, potential conflict."

RA is a mandatory advisory; you have to comply. Further, in our book if the traffic was not in sight, it is a "maximum performance" maneuver. For example, an RA Climb was maximum power, rapidly pull to the top of the green arc. There were grading standards during the simulator check rides for this.

The DHL crew immediately complied with the TCAS RA Descent command. The TU crew did not immediately comply with the TCAS RA Climb command. There's the bottom line, right there.

If the TU Captain had immediately initiated a max performance climb at the time of the RA (21:34:56, TCAS in both A/C issues a RA) he could EASILY have gained 1000 feet in the 36 seconds that it took to continue his descent and hit the DHL airplane. With the DHL in a descent,  most likely >1500 FPM there would have been PLENTY of altitude separation.

Look, the entire TCAS system is designed to avoid EXACTLY this sort of accident. However, it absolutely relies on BOTH crews following their individual RA advisory immediately. You can't dither around and have cockpit discussions about what "Climb! Climb!" really means. You get busted in the simulator for that.

There obviously were other considerations, but the bottom line is that if the TU Captain had complied with the RA with a max performance climb the accident would have been avoided.

That's it and that's all.