View Full Version : Sky-crashGuide report released

19th May 2004, 09:44
Check out www.bfu-web.de for the report on the 757/Tupolev collision over Germany in 2002.
It's available in English.

Full report in English at: www.bfu-web.de/berichte/02_ax001efr.pdf

19th May 2004, 13:57
Makes for solemn reading.

It was difficult for me reading that the crew of the 757 were alive after impact. How awful it must be to sit there with an out of control aircraft.

19th May 2004, 15:03
To enhance the performance of ACAS ICAO should initiate the development of down-linking RAs to ATC, using such technologies as SSR Mode S and Automatic Dependent Surveillance -Broadcast (ADS-B).Among a number of straightforward recommendations, this one will let ATC know when not to interfere with a TCAS RA.

Don't Look Now
19th May 2004, 19:02
With all due respect, RatherbeFlying, ATC have never had the right to "interfere" with TCAS, full stop.
In this particular instant the controller working that night did not "interfere" with the TCAS RA, but rather used the information available to him ie a mode C readout which was several seconds behind the actual vertical movement of the aircraft in question.
Most controllers in the world know that TCAS has priority over their commands. I, as a controller, am happy to work with the backup of TCAS, as I know that its' information is faster and more accurate than my radar processed and therefore delayed representation.
The BFU reccomendation would be another link in the safety chain to avoid further incidents.
It will be interesting if this reccomendation will be pursued by national and especially cash-strapped privatised Air Navigation Service Providers!

19th May 2004, 19:33
The 2 tables of TCAS data on p57 make very sombre reading.
Hard to believe that a few columns of numbers can be so depressing.

19th May 2004, 19:56
Don't Look Now -- As we have sadly seen, cockpit workload and other radio calls can delay a crew notifying ATC of an RA.

If the controller had had the RA notification on his scope, I'm sure he would have used the information appropriately.

20th May 2004, 08:03
If the controller had had the RA notification on his scope, I'm sure he would have used the information appropriately Partially disagree with what you are syaing... Given the completely unacceptable level of Management at this ACC, and the maintenance that was going on, most "electronic gizmos" developed over the years had been turned off. It is more than likely that if such a RA notification system had been developed, it would not have been available.

I am not disagreeing with such a system being developed. But lets keep uppermost this hard hitting report's findings. Technology did not really fail. Management, Quality Control and Safety Systems totally did...


20th May 2004, 08:59
Lots of intersting reading on this subject on Eurocontrol website;

Eurocontrol guys had an interesting presentation at the IFATCA conference in Hong Kong last March. Seems like most of RA are not reported or reported incorrectly or reports are delayed, so maybe (?) RA downlink is the answer.

20th May 2004, 10:49
I spent an hour reading through the report. Probably a very silly question, but why did the ATCO contact the TU154M first and instruct them to descend, as opposed to contacting the B757-200 and instructing them to descend? I only ask this with regard to "Right of Way" and the point that it would normally be the aircraft (the B757-200 in this case) approaching from the other aircraft's left who should take avoiding action. Does an ATCO bear that in mind when deciding which aircraft to contact in order to maintain separation?

(The Rules of the road at sea are similar, except for the vertical separation...?!) :O

20th May 2004, 12:00
No. Once a situation has deteriorated to the point of avoiding action- and remember, controllers are aiming to keep separation standards, in this case 7nm- you are just grabbing for the first straw you can. The report notes that the solution attempted wouldn't have maintained a sep standard anyway, even if there had been no RA.
I remember reading somewhere that the ATCO in question made the decision to descend the TU154 because it would have had to change level in the near future anyway, as it was about to change course? I can't recall the source so cannot say if that is correct.
If there is adequate planning ie. you had seen the conflict early, you think about things like who is landing first, who has right of way etc. Every controller does this sort of decision process hundreds of times a day. Sep decisions are not supposed to be arse-plucks. The holes lined up in this case.

Don't look now.
The crux of that issue is not IF ATC should interfere with RAs, but how can ATCs AVOID interefering if we don't know pilots are reacting to them? The fastest way for a controller to resolve a conflict is vertically. It's very difficult not to go for vertical if things are getting tight. It's a natural reaction. And (as seen here) it could be the worst thing to do. The situation as it stands is less than ideal.

20th May 2004, 12:49
ferris, Once a situation has deteriorated to the point of avoiding action- and remember, controllers are aiming to keep separation standards, in this case 7nm- you are just grabbing for the first straw you can. In an emergency, pilots are trained to follow pre-determined procedures. What perturbs me is your use of the phrase "you are just grabbing for the first straw you can" with regard to the ATCO. Do you mean that no pre-determined procedures exist to cover this type of event? The report doesn't go into why the ATCO contacted the TU154M first instead of the B757-200. Under the circumstances, if the ATCO had contacted the B757-200 first and instructed them to descend, the outcome would have been just a drama as opposed to a crisis with lethal consequences...

20th May 2004, 13:54
Do you mean that no pre-determined procedures exist to cover this type of event?

Well, no. The event happened when procedures broke down. When you realise you have made a mistake and it looks like 2 aircraft are going to collide, there is absolutely no time or rational brain process available to go through a checklist.

A loose parallel would be this.
Say you are walking along the street, looking at a map and look up to find yourself about to bump into someone doing the same.

The other person looks up at the same time and you both instinctively turn to miss each other. What procedure do you go through to decide which way to turn?

More often than not, both people turn into each other, then both take correcting action and turn the other way into each other again. Most often, you will somehow miss. Occaisionally you bump into one another.

OK, very simplified. However I think it is a good example of the "OH F :mad: :mad: K! " response when you realise the mistake and your sphincter starts twitching.

Whipping Boy's SATCO
20th May 2004, 13:54
I'm sorry but I think some of us are missing the point here. It is my understanding that TCAS is the LAST line of defence, designed to cater for a plethora of failings that have already conspired against the aircrew involved. Having read the report it seems to me that the real issue here is the less that satisfactory guidance that the TU 154 crew were given regarding the use of TCAS and some rather interesting CRM aspects. Undoubtedly, the ATC hierarchy had more holes that the proverbial Swiss Cheese (no pun intended). However, ultimately, if all aircrew had followed the TCAS indications and ignored ATC (as is their right), we wouldn't have been having this conversation.

20th May 2004, 13:54
It was the right call as per his flight plan. what surprises me after reading the report is how with a seperation of 7nm on a scope displaying 80 nm he omits to pass essential traffic to the DHL. that would have been basic procedure. And then after observing the mode C indicating descent he leaves that scope and attends to the arrival on a different scope...Wow!
It is also scary reading the list of equipement that was U/S that night.
Having said that, may his soul and that of all of the victims of this tragedy R.I.P.

20th May 2004, 14:34
VectorLine, I understand what you are saying by the use your "parallels". But an ATCO is supposedly in a position to be controlling the quoted pedestrians, not be one of them. And you are missing the point I was trying to draw attention to. Pilots are trained to incorporate certain fundamental priorities in an emergency. Like flying the airplane. By your account, once an ATCO needs to say "OH F:mad: :mad: K!", he has no pre-determined options because he has not been trained to follow any fundamental procedures. I repeat here my earlier reflection that "Under the circumstances, if the ATCO had contacted the B757-200 first and instructed them to descend, the outcome would have been just a drama as opposed to a crisis with lethal consequences..." The ATCO could have contacted either aircraft and both aircraft were at high altitude, so why not follow the straight-forward rule of "Right of Way" on which to base a response?

Whipping Boy's SATCO, TCAS is obviously still not fully implemented and tomorrow, another ATCO could give opposite instructions to a RA. Unless ATC is in a position to receive the same TCAS messages as the aircraft they are directing. For the present, clear rules obliging aircraft to give TCAS precedence must be reinforced. Otherwise, dramas will continue to become crises...whether or not there is someone in "the tower".

Whipping Boy's SATCO
20th May 2004, 14:56
airship, I think we agree.

20th May 2004, 15:12
Whipping Boy's SATCO, yes and I too agree that we are in agreement. Is that enough for a quorum? :D

20th May 2004, 17:20
I'm sorry to intrude here, on such a serious matter, but I can't understand WHY the TU-154 crew didn't comply with the RA.
I'm wondering how confortable would feel an aircrew, any aircrew, to disregard an RA, and do precisely the opposite?

Does it come down to a matter of what/who to trust the most? Do pilots trust TCAS? If so, in a similar conflict situation they will comply with the RA info, no matter what ATC says, simply because they trust the system; But if they don't trust the system, there is space for doubt in their minds, and probably will follow an opposite command from the ATC.

Are pilots instructed to obey TCAS over ATC? What should an ATCO do when a pilot reports back (if he/she has the time for it!) "Can't comply - we have an RA saying otherwise" ?

Excuse me for posing so many questions.


20th May 2004, 17:35
GD&L - your question is answered in the report. Read it all - it is a painful, harrowing exercise, but worth it. SOPs for those carriers have, I believe, now changed.

20th May 2004, 17:37
The answer to your question is on page 38 of the report:

"The control strip for the TU154M shows the intended routing NEGRA-Trasadingen (TRA) – BENOT. The estimated times of passing the listed waypoints were indicated with 21:36 hrs,
21:42 hrs and 21:51 hrs. Following the passing of Trasadingen VOR (TRA) a descent to FL350 was planned because the AIP Switzerland states that odd level numbers are to be used for the
intended flight route."

20th May 2004, 17:39
I suggest you search this thread (http://www.pprune.org/forums/showthread.php?s=&threadid=58312) where your questions have been discussed in detail.

Kalium Chloride
20th May 2004, 18:24
There's a fairly ironic fact buried deep down on page 61.

Although the two aircraft were both at FL360 initially, their altitudes were 50ft apart.

Might just have been enough for them to miss each other if they hadn't done anything at all.

20th May 2004, 21:44
An interesting and harrowing report. What I took from it was that the ATCO concerned was a fairly minor link in a horrifying chain of coincidental events that led to the disaster. Any one of a number of things could have broken that chain, but there are two which stick in my mind.

[list=1]The Russian Crew were trained, effectively, to follow an ATC clearance if an occasion arose where ATC and TCAS gave conflicting instructions, as is evidenced by the following:
"For the avoidance of in-flight collisions is the visual control of the situation in the airspace by the crew and the correct execution of all instructions issued by ATC to be viewed as the most important tool. TCAS is an additional instrument which ensures the timely determination of oncoming traffic, the classification of the risk and, if necessary, planning of an advice for a vertical avoidance manoeuvre."
A very dangerous piece of training when practically the rest of the world knows that TCAS instructions always take precedence over ATC avoiding action if the two are not complementary.[/list=1]
[list=2]The ATCO was working on two separate consoles, using two separate microphones and two separate radar screens. This would be definitely NOT ALLOWED in the UK under any circumstances, as the ATCO must effectively leave an operational position to use another one. In a word, negligence, but only as a result of bad management. If two ATCOs had been on duty, the conflict would have been seen much earlier and would have been a non-event.[/list=2]

Under the circumstances, if the ATCO had contacted the B757-200 first and instructed them to descend, the outcome would have been just a drama as opposed to a crisis with lethal consequences... Why? Because this instruction would just happen to be in agreement with the RA that the 757's TCAS was issuing? What I'm trying to say is, it was a 50/50 chance that just became another link in the chain. Controllers have many skills, but clairvoyance is not one of them. The ATCO chose to descend the TU-154 because, as has been mentioned, it was required to descend for the next part of its journey. The Rules of the Air have no meaning in controlled airspace - I doubt the controller would have considered them in the seconds in which he made his decision.

what surprises me after reading the report is how with a seperation of 7nm on a scope displaying 80 nm he omits to pass essential traffic to the DHL Never mind essential traffic, it should have been avoiding action. I have said on these forums before, and will say again, that best practice for ATCOs SHOULD be to issue avoiding action TURNS if there is any doubt as to whether the aircraft concerned are in a TCAS RA situation. And yet still, two years after Ueberlingen, the recommendation does not appear in the UK Manual of Air Traffic Services. All that appears is the glib statement, "...a controller must not issue control instructions....which are contrary to the RA communicated by the flight crew." Unhelpful at best. Some pilots may take several seconds to report an RA, which is time in which the controller can get himself/herself into trouble. There are any number of controllers, even examiners, who would advocate vertical avoiding action over horizontal, because they have the mistaken belief that it provides the quickest solution. As has been seen, not the case if you're contradicting an RA that you don't know about.


21st May 2004, 07:33
What I can't understand, and I think it wasn't really mentioned before, is - how can you make so self-contradictory SOPs? As was said many times, Russian procedures instructed to follow ATC rather tan TCAS. But other procedures said clearly - maneuvers opposite to TCAS RA are forbidden. So it doesn't really make sense - in the situation they were, you can't do both (follow ATC and not to oppose TCAS RA). I think it might have added to some confusion on their side (decision of PIC to follow ATC, copilots queries about TCAS), adding to little time they had to decide on course of action, and everything coming at the same time.

21st May 2004, 08:03
criss - there you have it - yet another hole in the famous 'Swiss Cheese' aviation accident model - NB no sick humour intended there.

Life is always full of surprises, not all of them nice, and it is just a terribly sad thing that these things (as with the 'procedures' in place in ATC) only come to light in these tragic circumstances. If you go through any procedures anywhere with a fine tooth-comb it is likely you will find other 'contradictions'. It was the combination of 'holes' there that sadly made this a fatal event. 50-100' difference and there would have been a load of people alive but severely frightened and the holes would have been closed.

The best we can say out of all this is that a few more 'holes' have been shut. I do not mean to sound trite, but it is not a perfect world.

21st May 2004, 10:00
Would it be a good procedure, in a conflict situation, for an ATCO to ask something like this "XXX do you have RA info? follow it , contact me after ..." , prior to give instructions blindly?

21st May 2004, 13:29
lost the picture
Good points well made.

I think from re-reading the posts we are all in agreement that

1. TCAS is a last line of defence.
2. Pilots MUST ALWAYS follow RA advice
3. Controllers MUST give "AVOIDING ACTION" when necessary - and in the horizontal, not vertical plane.


I think we came at opposite sides of the discussion here. I absolutely agree about following procedures and am happy to say that there are very robust ones in place. NATS, Swanwick in particular, has excellent annual Training in Unusual Circumstances and Emergencies (TRUCE).

However in the incident we are talking about, the controller was looking at a different radar display. Therefore, when he looked at the en-route display, it was pretty much already too late.

The picture we see is a 2D plan. In a moment of fear and instinctive action, the aircraft with right of way is not always blatantly obvious. When you are working hard and thinking quickly it is very easy to get your left and right mixed up - particularly when aircraft are moving north to south - I expect the majority of radar controllers here would admit to making the left/right mistake more than once in there careers so far.

The controller made the decision that seemed to be the right one in his mind at the time of the incident. We can not criticise him for that. We can however learn from the result - re: the top of my - points 2 and 3


21st May 2004, 14:36
After reading the BFU report, does anyone else think the TU154M PF got away lightly for disregarding the RA? I hasten to add that I mean this in the sense of apportioning blame in the report only. He has already paid with his life...

21st May 2004, 20:46
One helpful technique during any TA is to select the 5-mile range as the target is approaching. This will enhance position orientation in case of an RA. And in case of an RA, while following vertical commands, one might be inclined instinctively to steer away from the approaching target, especially during IMC.

22nd May 2004, 07:07
Why should the 757 have been descended instead of the 154? If the controller wanted the 154 at the lower level so be it. Rules of the air are rather academic in this environment, fine in VMC. The stress and workload that the ATC guy were under are not exactly unknown, listen to the density of rt in the London zone for instance, sometimes impossible to get a call in for minutes. Reporting a TCAS advisory is not exactly top priority when you are manouvering the aircraft and looking for the conflict. in any case the situation is now out of the controllers hands and happens very quickly, he certainly doesn't have time to coordinate things. An incident of this sort obviously concentrates attention on these particular circumstances but near misses aren't exactly rare and the reason most do not end in disaster is because, in the final analysis, the pilots correctly following the TCAS commands prevent this. Thus the shortcomings that caused them are hidden. The 154 crew may have been confused, the 'spare' FO though seemed to understand the importance of following the TCAS, pity he wasn't PF.

22nd May 2004, 07:16
I really think we should cease this attempted 'criticism' of anyone here, and take the hard-learned lessons. ATC procedures were inadequate. The TU followed what he understood to be the over-riding of two apparently conflicting 'rules' for his operation.

We gain nothing from trying to apportion further 'blame'? It is obvious that TCAS, if followed by both a/c, would have prevented the accident. The tragic loss of life will, I hope, eliminate any possible confusion over TCAS in the future.

22nd May 2004, 16:13
"Would it be a good procedure, in a conflict situation, for an ATCO to ask something like this "XXX do you have RA info? follow it , contact me after ..." , prior to give instructions blindly?"

Is there any reason why the system couldn't be engineered automatically to register TAs with local ATC? Is there any practical reason why it shouldn't?

22nd May 2004, 18:20

If I understand your questions properly, then;

When ATC's realize that the aircraft under their control have lost (or are about to lose) separation, the natural course is to take positive action, that is the overriding impulse. To provide "if ... then" instructions is not quite positive enough, because the result is one of two (unknown) possibilities. Sitting down after the fact and considering how it might or should have been handled is not even nearly the same as being there and then, and realizing that these guys are going to get way too close for comfort.

Regarding RA's being passed to the ATC system, IMHO, the problem with that is that the update of the Radar (in conventional systems) is too slow and thus will not be as accurate as the STCA, possibly providing outdated and inaccurate advice.

When this accident happened, there was a pilot that made a statement on these forums, he said that before he did any pre-start checks or anything else, he would say to the other pilot "We agree here and now that when we get an RA, we don't think, we just do it"

Honestly, I cannot think of any better advice for flying personnel. In the same way, I hope that ATC's make the same sort of deal with themselves, regarding avoiding action scenarios.


22nd May 2004, 19:50
Am I the only one to think that if the exact same conditions were repeated, the accident would certainly not occur? The likeliness of a mid air collision at those speeds is just amazingly low; at 360m/s just 0.1s later there would have been no physical contact! maybe the turbulences would still have destroyed the plane behind, but nonetheless, their time had come.
When money is involved, it's always worth IMHO to evaluate how many lifes can be saved in what circumstances.. Correcting this situation with high cost installations is not worth it even if I was to be on a fatal path, me thinks. This money could save much more lifes applied to other issues.. 'tinfoil hat on'

22nd May 2004, 21:23
When this accident happened, there was a pilot that made a statement on these forums, he said that before he did any pre-start checks or anything else, he would say to the other pilot "We agree here and now that when we get an RA, we don't think, we just do it" Whilst sound advice, and I can see that for you as an ATCO, it seems a priority, history might suggest that if you confine your pre-flight brief to 1 bullet point, the GPWS might be the one to concentrate on! Mountains always have, and I suggest always will, kill more than midairs.

It is quite hard to back away from jumping to conclusions from this report, and proposing "solutions". The real solution was re-emphasised within weeks of the accident. Follow the RA every time... We can see that the "system" failed here, in that the TU-154M Flight Manual was confused over this issue. It is not surprising it was confused, in that the airline only carried TCAS outside the CIS area, and TCAS type procedures were not common to CIS based airlines. That lesson is now learnt.

I do not think it worth getting into discussions / technology for integrating TCAS and ATC. ATC is our prime collision avoidance measure. TCAS only steps in when ATC has (rarely) failed us. Why now involve the "failed system" anymore?

An analogy is a GPWS warning. We primarily avoid mountains by navigation and general awareness. When the GPWS warning goes off, if the pilot now still tries to bring his "situational awareness" into account, he usually fails, and dies. We need to now assume that the GPWS is correct, our navigation has failed, and follow the GPWS faithfully until the GPWS has shut up and we can only now try and restore the navigation awareness . Until that point, believe the "last ditch safety system" 100%!

The Mgmt type lessons of course, are overwhelming, and I trust being dealt with...

Spuds McKenzie
23rd May 2004, 08:32
So far this thread has been very objective (partly thanks to the Mods...). Congrats to all who have contributed to it.

Re the SMOP (Single Manned OPeration), meaning only one ATCO working on position, be it a control sector during the day, or be it at night when all the sectors ar combined to one, it has to be remembered that this always has been and still is common practice in various ATCs worldwide, hence it is not only a Skyguide issue. This includes TWR, APP and ACC (Area Control).

I totally agree that this has to be addressed, and it has been dealt with at Skyguide, no more SMOP there.
It will be interesting to see if ICAO and/or EUROCONTROL and other local ATC bodies pick up the issue.

die skyguide
23rd May 2004, 17:07
So Spuds McKenzie maintains that Single Manned Operation is common practice in various ATC units worldwide...

Not in the civilised world old boy, where safety culture has been developed and refined through long and bitter experience. For an ATCO to leave an approach control position in order to deal with high level traffic is strictly forbidden. Not even the most basic ATC unit in darkest Africa would have behaved with such crass incompetence. From what we now know the ICAO position broadcast procedure on 126.90 could just as well have been applied to flights operating in the richest country in Europe!

The catalogue of errors made by Skyguide on that fateful evening defies belief and is now the subject of a criminal inquiry by the Swiss government.

My sympathy is with the Russian Captain. It was 2 to 1 against - the unfamiliar TCAS telling him to climb versus the Skyguide controller and his Chief Pilot (who was sitting next to him) ordering him forcefully to descend.

Spuds McKenzie
23rd May 2004, 17:22
Still roaming about with different names, eh?

SMOP is still being exercised in Germany, Australia, NZ and others.

Single Person nightshift staffing continues in Australia, including in Sydney and Brisbane.


23rd May 2004, 18:11
die skyguide......(nice pseudonym..NOT)
My sympathy is with the Russian Captain
Go and read the story again and get your facts together. The co-jo wanted to follow the TCAS and was overuled!
SMOP indeed takes place in Germany on what they call the "quiet" sectors, with the blessing of the supervisor on duty!
Do all of the countries mentioned above not fit into your version of a civilised world? Not in the civilised world old boy

23rd May 2004, 18:26
There is much concentration here on the role of ATC and confliction with TCAS etc.

What I have always found difficult to understand is why both or either crew continued with a course of action which plainly wasn't working. If you are established in a descent in reaction to a TCAS RA or an ATC command, and the relative level of the aircraft is not changing, why do you continue with it?

In broad figures, if a conflicting target indicates +00ft on your TCAS, you start to descend and it remains at or close to +00, then obviously another plan is needed, even of the instruments dictate otherwise. Even a 10 degree turn might have meant they missed each other.

In addition, the vis up there was greater than 10 km. Both aircraft had anti-collision lights and were aware of the other's presence. There was little or no other traffic about, and there was fairly good cloud cover preventing a myriad of ground lights from hiding the lights of the other aircraft. Even allowing for zero relative motion, why were the crews (and there were 4 of them on the 154) not able to look out of the window and see each other in those conditions? Was there (and is there still) perhaps too much reliance these days on the 'gizmos' to solve the problem and less on the basics of pilotage?

No disrespect intended to the deceased crews, but a basic question.

23rd May 2004, 21:02
why were the crews ... not able to look out of the window and see each other in those conditions?
Read the report carefully: They saw each other.

It is impossible to guess speeds and altitudes under these circumstances, as the report clearly shows (backed up by graphics).

Other avoiding action? Difficult when approaching at a 90 degrees angle. The good reasons for following the RA have been given in this thread. Selecting other/alternative measures means you are undermining RAs which are meant as the FINAL resort!

23rd May 2004, 23:27
In reading the report it is quite clear that the underlying failure was once again that of management.

I recall reading another report recently where management at an Italian airport were ultimately to blame for an accident.

Wouldn't it be nice if (for once?) senior management was made to take responsibility for their failures. Maybe one or two long prison sentences might just concentrate the mind of these people.

I speak as a senior manager within the transport industry (not aviation) where my actions are subject to very close scrutiny with very serious legal implications when I get it wrong. I am also a regular air passenger.

This does not appear to happen in the air transport industry, or am I wrong in this assumption?

Devils Advocate
24th May 2004, 11:12
Kalium Chloride - that's a valid point, i.e. about the 50' - 100' being as good as a mile.

Indeed it's all the more relevant here because the controller actually cleared the TU154M down to FL350 - indeed this occured some seconds prior to the RA.

To make sense of what follows, see appendices 1&3 (http://www.bfu-web.de/berichte/02_ax001ea1.pdf) and 2,4,5,6,7,8,9.10 (http://www.bfu-web.de/berichte/02_ax001ea2.pdf)

If one examines the superimposed ‘Altitude + V/S’ charts for the B757 & T154 ( in Appendix 6 ) in conjunction with the other FDR extracts versus timeline one sees the following:

From the altitude graph it would appear that, when both aircraft were ostensibly at 36000’, the T154 was actually cruising approx 50’ higher than the B757 - i.e. the former was at approx 36070’ and the latter at 36020’.
Given that both should be using 1013 ( Qff ) then one might put this variance down to the T154 using metres ( converted from feet ) plus some ‘altimeter error’ in either aircraft's altimeter.

21:34:42 – TCAS TA onboard both aircraft announces “Traffic Traffic”

21:34:49 - ATC - tells the T154 “Descend FL350”

21:34:56 – TCAS RA onboard both aircraft tells T154 “Climb” & B757 “Descend” respectively.

Nb. Inspection of the V/S graph shows:

21:34:58 - B757 - commences descent from FL360 ( i.e. within 2" of the RA ).
21:35:02 - T154 - commences descent from FL360 ( i.e. as per the ATC instruction and contradicting the TCAS RA saying that they should "Climb" )

Nb. In the full report ( the ACAS/TCAS section ) it suggest that the T154 crew commenced descent immediately when instructed by ATC ( i.e. at 21:34:49 ), however the graph on appendix 5 ( and others ) seems to contradict this wherein it shows the T154 leaving FL360 no earlier than 21:35:02, i.e. 13" after being instructed to do so by ATC.

From the gradients on the V/S graph it would appear that the initial ROD of the T154 was twice that of the B757 and accordingly at 21:35:04 – whilst having started out at a slightly higher altitude than the B757 - the T154 crosses the level of the also descending B757 ( this occurs at approx 35940’ ) and, from this point on, the T154 is always lower than the B757 ( that is until just prior to impact ).

21:35:02 – ATC - tells T154 to “Expedite Descent” ( possibly due to their delay in having commenced it in the first place ? )

21:35:07 – T154 - crew acknowledge the request to “Expedite Descent”

21:35:10 – B757 - TCAS “Increase Descent”

21:35:19 – B757 - informs ATC of "TCAS Descent”

21:35:24 – T154 - TCAS “Increase Climb”

21:35:27 – T154 - F/O “Climb it says”

21:35:28 – T154 – commences a climb, having ducked below FL350 by approx 120’.

21:35:31 – Both aircraft collide.

Whilst it’s admittedly something of conjecture, had the TU154 levelled at its assigned FL350 ( which is, after all, what the T154 crew were prioritising ) it would appear, according to the graphs, that the B757 would have passed overhead by approx 50’ ( a miss & a mile and all that ). However, as it happened, the TU154's attempt at climbing back to its assigned level made matters worse - the collision occuring at approx 34890'.

A lot of people need to do a lot a soul searching about this whole episode, but wherein lets remember that the TU154 not only failed to comply with the TCAS RA but also failed to level-off at its assigned altitude - there's a lot to be learnt from this, unfortunately. :(

Capt Pit Bull
24th May 2004, 13:14
Just to reiterate a point I made in previous threads about this accident:

Please remember to differentiate between:

(a) Not complying with an RA.


(b) Manouevering in the opposite sense to an RA.

There are circumstances where not complying an RA may be necessary. This is recognised by manufacturers and authorities and hence final authority to follow or disregard an RA rests with flight crew.

However, manouevres in the opposite sense are forbidden.

Excluding the circumstances preceeding the TCAS event itself, this accident was NOT caused by the failure of the T154 to follow its RAs.

It was caused by the T154 manoeuvering opposite its RAs, not just once, which the strengthened 'Increase Descent' RA issued by the B757 would probably have dealt with, but twice.

Anyone that thinks I am splitting hairs is missing the point. The golden rule of surviving a TCAS event is 'Don't Manoeuvre Opposite'.

24th May 2004, 18:07
Capt Pit Bull, while most of us will appreciate what you mean, just how would this translate into all the non-English mother-tongue administration rules? Please remember to differentiate between:
(a) Not complying with an RA.
(b) Manouevering in the opposite sense to an RA.

By (a), I take it you mean ignoring a RA as opposed to (b) doing the exact opposite ie ascending instead of descending. Just how could and would these interpretations translate?

Those who write the rules should KEEP THEM SIMPLE and UNAMBIGIOUS so that there IS NO DOUBT! :O

ATC Watcher
24th May 2004, 20:30
The ( quite good ) report goes in great details to explain certain things but pass very fast on others.

Some of them I would like to have seen mentionned :

The name RA for "Resolution Advisory " was choosen by the FAA to limit the liability of the US manufacturer of the Software ( The Mitre Corporation ) Only in the US was it known implicitely that although for legal reason we call it an advisory, it is in fact a command .
Unfortunately when you translate the manuals and the procedures in other languages, Advisories remain advisories.

TCAS was made by the US for the US... (on one of its first report Eurocontrol mentionned that TCAS II logic behaved badly in European types of en-route airspace...)

To follow an RA you need to be 2 in the cockpit : one that look outside to identify the intruder, the other that look at the display and follow the needle to keep it in the green.
Attempting to do both at the same time results in large deviations...
The 757 pilot was alone for a great part of the RA..( I do not believe this played a role in this case , but it show us that Murphy' s law is always valid...)

The unsheduled late inbound to to Friedrichshafen was, from an ATC point of view the most important link of the chain of event that led to this collision.
The paramount importance of this fact is missing
This forced the controller to look into two different scopes a few meters appart, and monitor alone two different active fequencies whit degraded telephone system and faulty back ups. This led to the late detection of the conflict and the late decent clearance to the TU.( which was the action most controllers would have taken since the TU was pllanned and coordinated with the adjacent centre at 350 and the DHL had just reached his cruising altitude ) .
Various Management levels put the controller into that position that night. This later also cost him his life.

Finally to "Die Skyguide" : first post and already full of hate.. :hmm:

For info in most ATC centres at night before that day, SMOP was either planned by Management ( still is in some places, especially in TWR-APP )or at least tolerated.

25th May 2004, 08:32
Upon reflection, one of the things that I took away from reading this is how compliant we are all becoming in the erosion of safety in the industry.
IMHO, a lot of stuff goes on now that just wouldn't have in times past. If you want to get anywhere, you just have to put up with it, or be labled as 'belligerent' or 'change resistant'. Manning levels, fuel policies etc are all being squeezed as the dollar keeps becoming more and more important.

Maybe I'm just getting old........

29th May 2004, 05:29
Big sky – little sky

This tragic case should end the “big sky” notion that the air traffic controller’s ultimate savior will be the vastness of the airspace and the smallness of the airplanes. Satellite navigation accuracy, RVSM and automated, computerized flight controls have combined to kill the big sky theory. Dense clusters of airplanes headed in both directions and separated by half the 2,000-ft. vertical separation of yesteryear can make the sky along preferred tracks very small. Constructing a mid-air collision is now as straightforward as putting two trains on one set of tracks. In this accident, the controller tried to close the switches after the locomotives had passed by on their intersecting tracks. Technical refinement of navigational tracking accuracy and height-holding precision has increased the efficiency of preferred airspace use, but at an increase in the risk of mid-air collisions. Controllers now need to become sensitized to the “small sky” theory. For pilots, there is a reason why the “see and avoid” principle of collision avoidance may not be sufficient.

The ‘strange attractor’

For pilots, sighting the threat can lead to a greater hazard that might be called the “strange attractor.” This term describes a scenario where two pilots at night without a defined horizon become fixated on keeping each other’s lights in sight. In this mid-air collision, note that the TU154 changed its heading from
264º to 274º about two seconds after sighting the B757. The result can be a mutually maintained constant relative bearing on each other, which can greatly increase the risk of collision or near-miss. The control inputs by both pilots in the last few seconds tends to bear out the sudden arousal of imminent collision as
each “target” blossomed in size.

The two crews had been "visual" for almost 30 seconds. That is a long time in aerospace terms. Pilots disregarding a coordinated TCAS RA while attempting visual avoidance do so at their peril.

29th May 2004, 20:54
Wow, you guys are hard on the pilots. You would hate to fly with me, I make mistakes constantly.

Profit Max
30th May 2004, 12:39
I am not a pilot, but have followed this mid-air accident closely. I have the following suggestion for the TCAS logic, and would like comments on this.

In my opinion, the flaw is that the TCAS software assumes that the other party will follow the RA. This could be improved upon. I suggest that if TCAS realises that the other aircraft is not following the RA, but rather moving opposite to it (for whatever reason):

- assume that the other aircraft will not follow any RA in this situation

- issue a reversing sense RA to the non-complying aircraft so that the RA is consistent with its actual vertical speed

- issue a corresponding RA to the complying aircraft to achieve maximum separation

This logic would have avoided the Überlingen mid-air as follows:

(1) First RAs issued (descend to B757, climb to Tu154)

(2) after several seconds both TCAS computers realise that the Tu154 is not complying, as it is in fact descending.

(3) The computers should now re-calculate the forecast for the altitude at the potential collision location of the noncomplying aircraft, the Tu154, assuming that the current vertical speed of the Tu154 is maintained. The result of this calculation would have been a projected altitude of somewhere between 34,500 and 35,500 feet.

(4) The computer now re-calculates the optimal RA for the B757, which would have likely been a reversal sense RA ("Climb, climb now").

(5) Issue both RAs: "Climb, climb now" to the B757 (possibly followed up with a "Increase climb, increase climb") and a "Descend, descend now" to the Tu154 (possibly followed up with a "Increase descend, increase descend").

(6) Now there would have been no more confusion for the Tu154 crew, and while the B757 pilots might have been sweating while following the reversal sense RA, a safe vertical separation would have been achieved.

OK, comments please. Note that I do agree with many other additional safety measures suggested, and this only one further suggestion. It would have helped in this case, but might it lead to a higher probability of accidents in other cases?

Profit Max.

30th May 2004, 15:57
Profit Max,

we are always talking here of the RA as a (i.e. THE!) last resort. As such we are talking of a matter of seconds. If a once given advisory was changed this would probably cause more confusion than help - especially when we continue toying with ideas and think of a situation where the crew who had not complied in the first place (here: the TU154) suddenly make up their mind and start following the (original) RA (not an unlikely scenario, as we know now that a short discussion about the RA had taken place in the TU154 cockpit). This would then create yet another RA, and so on, rendering TCAS unnecessary/useless.

ATC Watcher
31st May 2004, 05:53
Profit Max, what you described already exists and was planned to work with version 7. ( sense reversal RA ) It did not work in Ueberlingen for a lot of reasons which have been in the meantime identified. A change proposal (CP )to rectify the CAS logic was issued by Eurocontrol , evn prior Ueberlingen, it is called CP112.
The problem is that the FAA who owns the software has disbanded the TCAS programme and there is nobody to work on the software change.

31st May 2004, 08:50
I think we need to be careful of adding "more technology" to solve a "problem", when the current technology should have prevented it, but other (Human) factors prevented it.

The "Human Factors" here were poor worldwide management in ensuring that all Flt Crew and Manuals were at one over obeying the RA rather than ATC. That was quickly corrected... so the problem should not recur. (NB of course TCAS works perfectly well if one aircraft ignores the RA).

As has also been stated, the RA is a last resort. Why did we get to the last resort? Again, Human failings - largely Management again with the staffing levels and disabled technology at ATC. All this combined with one small error and the tragic results.

Let's concentrate on correcting the identified error's (largely done?), rather than inventing more technology to cope if this particular set of c*ck-ups occurred again.