Mid-air collision of 3 international flights averted over New Delhi!
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I closed my logbook having reached retirement age and +21k hours on commercial jet ops. Accident/ incident free BTW.
Always happy landings for you.
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We train our boys and girls to make no reference to actual levels when referring to expectations of climb/descent; e.g. "copy your request; expect higher in approx. (so many) minutes/miles. Reason being, you can get interrupted / distorted comms and everything goes belly up, like this incident.
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Guess the big main feature being, accidents always waiting in a small corner to be , also with the (mis) communication being in the front 2 seats or with atc. Safe landings
The Aviation Herald has one image that shows the positions quite neatly.
Incident: NAC B744 near New Delhi on Dec 23rd 2018, climb without clearance causes loss of separation with two aircraft
The reader's remarks below it (shown in anti-chronological order) strongly suggest what kind of misunderstanding developed resulting in the premature and unauthorized climb by the NCR 840 that created the loss of required separation.
Incident: NAC B744 near New Delhi on Dec 23rd 2018, climb without clearance causes loss of separation with two aircraft
The reader's remarks below it (shown in anti-chronological order) strongly suggest what kind of misunderstanding developed resulting in the premature and unauthorized climb by the NCR 840 that created the loss of required separation.
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250kts, just for info, from my recollection (for what it's worth), I have never heard "expect so" from my time there. But, a younger generation of controllers (from many nationalities) work there and it's possible that one or some use this odd phraseology! When it was known/planned that higher was available a little further on, generally it was quite simply "maintain FL???, you may expect higher". Again, depending on the individual, some would add, " in X minutes" or "with the next sector" etc. The requested FL would never be mentioned by the controller unless in an actual clearance.
It was the KLM 777 and NAC 747 that were 2.2 nm apart at the same FL, but both had been on the same south-easterly heading until the 747 was turned left by ATC.
WOW....
From the US AIM pilot controller glossary
I know, not in the USA, but I can find that document
From the US AIM pilot controller glossary
EXPECT (ALTITUDE) AT (TIME) or (FIX)− Used under certain conditions to provide a pilot with an altitude to be used in the event of two-way communications failure. It also provides altitude information to assist the pilot in planning.
Folks,
For those of you familiar with the area, what is the current published airspace classification, in which the incident occurred??
Tootle pip!!
For those of you familiar with the area, what is the current published airspace classification, in which the incident occurred??
Tootle pip!!
Last edited by LeadSled; 31st Dec 2018 at 06:26. Reason: spelling corrected
Having seen additional information given above some observations might be drawn from the plan view time-lapse sequence:
KLM 875, SE-bound at FL 330, did not change from his assigned FL.
BR 61, initially NW-bound at FL 320, did not change from his assigned FL but turned towards the West as instructed by ATC.
N8-840, initially SE-bound at FL310 whilst climbing turned towards the East as instructed by ATC.
It would appear that it was the turn instructions given by ATC that mitigated most effectively the risk of these encounters becoming too close.
As regards TCAS, it could be that the pilots of KLM 875 at FL 330 were advised not to descend, and that those in BR 61 were advised to neither climb nor descend - if indeed they saw more than a TA as at the closest point of approach they were diverging from the flight path of N8-840.
I would have expected the TCAS in N8-840, if operating, to have posted advice not to climb. As this aeroplane was relatively close to the two B777s I would have expected its TCAS display to have indicated the presence of the KLM 2,000 ft above and also of the BR 61 1,000 ft above on the reciprocal track.
I wrote, ‘if operating’ since the decision to initiate a climb and to have ascended 2,000 ft into close proximity of the KLM suggests that the display was either not visible or that the information it posted (proximate aircraft symbols and possibly TA/RA alerts) was not acted upon.
I do hope that more and accurate data is forthcoming!
KLM 875, SE-bound at FL 330, did not change from his assigned FL.
BR 61, initially NW-bound at FL 320, did not change from his assigned FL but turned towards the West as instructed by ATC.
N8-840, initially SE-bound at FL310 whilst climbing turned towards the East as instructed by ATC.
It would appear that it was the turn instructions given by ATC that mitigated most effectively the risk of these encounters becoming too close.
As regards TCAS, it could be that the pilots of KLM 875 at FL 330 were advised not to descend, and that those in BR 61 were advised to neither climb nor descend - if indeed they saw more than a TA as at the closest point of approach they were diverging from the flight path of N8-840.
I would have expected the TCAS in N8-840, if operating, to have posted advice not to climb. As this aeroplane was relatively close to the two B777s I would have expected its TCAS display to have indicated the presence of the KLM 2,000 ft above and also of the BR 61 1,000 ft above on the reciprocal track.
I wrote, ‘if operating’ since the decision to initiate a climb and to have ascended 2,000 ft into close proximity of the KLM suggests that the display was either not visible or that the information it posted (proximate aircraft symbols and possibly TA/RA alerts) was not acted upon.
I do hope that more and accurate data is forthcoming!
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As regards TCAS, it could be that the pilots of KLM 875 at FL 330 were advised not to descend, and that those in BR 61 were advised to neither climb nor descend - if indeed they saw more than a TA as at the closest point of approach they were diverging from the flight path of N8-840.
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Nugget 90, You seem to be exonerating NR 840. My understanding is that it was maintaining assigned level of 310 and asked for 350 which understandably was not granted but it climbed anyway. ATC saw it and averted the danger by turning him and EVA 661 left, away from each other. Flights at 310 320 and 330 ( including opposing traffic) are legally separated but 840's action upset that apple cart. Flights are in this close proximity every day everywhere I should think, so TCAS ought not to be a factor surely? ATC saying expect 350 was presumably misunderstood by 840.
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Until all the facts are known ( e.g. what was the readback of NCA and what was the reaction of the controller to that readback) we can only speculate wildly on this case
A few points however :
The title of this post is based on a sensationalist newspaper headline and is what I would describe as "fake news" . 2.2 NM same direction with the faster one in front is hardly a risk of collision . loss of separation yes, risk no. The EVA opposite was turned away after STCA alert , no loss of separation and no risk either.
That said
Delhi FIR is RVSM and seen the 3 types involved the 1000ft sep is absolutely normal . they were in controlled airspace under positive radar surveillance, as the STCA and vectors issued confirmed.
There also seems to be some RAs involved and it would be interesting to know who got one, who followed the RA and possibly who did not and if possibly the controller issued instructions contrary to the RAs. That could in fact be the core of the problem here . We'll see when we get the facts .
In the meantime wish you all a happy new year , and my advice for 2019 would be : always follow the RA even if the controller tells you otherwise .. Safe landings too
A few points however :
The title of this post is based on a sensationalist newspaper headline and is what I would describe as "fake news" . 2.2 NM same direction with the faster one in front is hardly a risk of collision . loss of separation yes, risk no. The EVA opposite was turned away after STCA alert , no loss of separation and no risk either.
That said
Delhi FIR is RVSM and seen the 3 types involved the 1000ft sep is absolutely normal . they were in controlled airspace under positive radar surveillance, as the STCA and vectors issued confirmed.
There also seems to be some RAs involved and it would be interesting to know who got one, who followed the RA and possibly who did not and if possibly the controller issued instructions contrary to the RAs. That could in fact be the core of the problem here . We'll see when we get the facts .
In the meantime wish you all a happy new year , and my advice for 2019 would be : always follow the RA even if the controller tells you otherwise .. Safe landings too
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It is normal practice in many oceanic centers to precede any request for a level change with MAINTAIN LEVEL ###; followed by any further instruction on level change exactly because of the problem in this case.
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Wait. Wait. Wait. Why are people questioning whether NCA's TCAS was working? All the stories say its climb was a result of a TCAS warning.
One would assume a TCAS warning requires an instant response, not waiting 2 or 3 minutes for ATC to get back to you.
If planes on opposite courses are going to be assigned FL's 1,000 feet apart, TCAS needs to be programmed no to go off in the situation.
One would assume a TCAS warning requires an instant response, not waiting 2 or 3 minutes for ATC to get back to you.
If planes on opposite courses are going to be assigned FL's 1,000 feet apart, TCAS needs to be programmed no to go off in the situation.
