Mid-air collision over Brasil
Wouldn't it be more appropriate, and perhaps wiser, to preface your statement with some indication that this is speculation, or based on some official finding of fact published by the investigating authority? It really would be helpful to substantiate your assertion with something more than this single sentence.
I will take no position on whether either crew, or ATC for that matter, was or was not operating in compliance with any rules, SOPs or accepted operating practices until such time as an official report which includes time corelated CVR, FDR, ATC RADAR and ATC radio and telephone recordings is published and available for review. To do otherwise is to leave oneself open to making unfounded assertions and a number of "errors of logic". You do as you wish, but I prefer to wait for established facts before reaching conclusions.
It's up to you, but maybe it would be better to objectively comment on established facts, identify any speculation as such and try to avoid blurring the line between the two. Opinions are certainly going to be shared, but should be identified as such. Just a suggestion.
Best regards,
Westhawk
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Standing by for a reply -
LL
(Post #457) I don't understand how this works. How would ATC and the airplane crew start their 7 minute clocks simultaneously? Especially if the transponder doesn't work.
Hypothetically, if the crew realized they had radio communications failure, squawked 7600 and then, 7 minutes later, changed to their flight planned altitude, wouldn't that be extremely dangerous if ATC didn't receive the transponder and didn't realize there was a radio problem?
Its ambiguous the other way as well. What altitude is ATC to think the plane is flying if they realize that there is communications failure but they don't know whether the crew knows this or not?
Hypothetically, if the crew realized they had radio communications failure, squawked 7600 and then, 7 minutes later, changed to their flight planned altitude, wouldn't that be extremely dangerous if ATC didn't receive the transponder and didn't realize there was a radio problem?
Its ambiguous the other way as well. What altitude is ATC to think the plane is flying if they realize that there is communications failure but they don't know whether the crew knows this or not?
For a case in point, please refer to the TSB Aviation Investigation Report: Communications Failure and Loss of Separation link below:
http://www.tsb.gc.ca/en/reports/air/...1/A03H0001.asp
Pegase Driver
Santos Dumont ( I like the name ) thanks for your excellent and very informative post. Also very wise words.
Hopefully the transcripts will explain the sequence of events. Based on what you wrote and the FPL , I can draw up an ATC scenario in my head , but I will wait until the transcripts are available to validate or not that idea.
Hopefully the transcripts will explain the sequence of events. Based on what you wrote and the FPL , I can draw up an ATC scenario in my head , but I will wait until the transcripts are available to validate or not that idea.
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This makes better sense. A few pages back, someone posted ICAO procedures that specified 7 minutes after one of four things occurred. I have heard that those procedures changed in the last couple of years (but I don't know much about ICAO rules).
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The American pilots are in no way arrested. They are staying with their wives in a 5-Star JW Marriott hotel in front of Copacabana beach. They have the freedom to go wherever they want and do whatever they feel like as long as they remain in the country.
a) who pays for the stay?
b) how long they are expected to enjoy their exclusive holiday?
EDIT @B&t yes it is...thought the use of "expected to" would make it clear
Last edited by the_hawk; 12th Oct 2006 at 09:54.
Enjoying their exclusive holiday? I hope this is a tongue in cheek remark. I know where I'd rather be, and it wouldn't be stuck thousands of miles from home being investigated for a fatal accident.
Last edited by Blues&twos; 12th Oct 2006 at 09:34. Reason: Spelling
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S. Dumont, excellent post, but here's were it hangs:
If that is true: until 100 NM before the collision, i.e. 300 NM or 45 minutes after BRS and the planned level change ATC would have seen Legacy 600XL still being at FL370 without taking any protective action. And: knowing opposite same level traffic coming in from Manaus.
My sources (indeed I have sources) indicate (indicate is different than state) that the Legacy XPDR turned C mode off 15 minutes before the collision.
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20 minutes for non radar environment
Though I don't understand who tells one in what kind of environment your are?
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My theoretical concern was when you lost comm and were about to leave radar coverage, who makes you aware of which rules applies?
I'm in one of those moods
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threemiles
…. Most interesting posts!
.
The odd shaped piece in this jigsaw may well be summarised in this one musing (assuming it is even remotely accurate)
… a mode change rather than a TXPDR U/S is a very different scenario … perhaps one of our technical experts can advise us if the Honeywell TXPDR in question could fail C only, and what would that system then do i.e. shut it all down or just the alt; and would TCAS continue to function in the Embraer??? … obviously without Mode C the B738 might only get a TA … anyone?? ….. it might explain why the B738 was ‘apparently’ banking …. Crew may have been looking as a result of a TA …. only to realise too late that there was indeed traffic closing at 900+kts at the same level .. remembering TCAS rules .. on track and vertical resolution!!
.
….. what Embraer Flight deck indications would result from Mode C fail??
Squarking Mode C and FL370 in Radar airspace
… hmmm
.
.. didn’t someone earlier suggest the B738 was FL350 climbing FL390
.
.. from what I have seen of the H4 chart and the supposed information on MAC position, and the timings of loss of TXPDR (mode C apparently) … I am lead to ponder what ATC instructions were likely to have occurred, read backs that would likely have been required and perhaps received, and how they (time) correlate to the loss of Mode C??
… from the information (accurate or not) posted here I would think (logically based on normal ATC distance buffers for achieving vert in radar airspace) they could be almost coincidental …..very very interesting!!
.
…. to me the only thing that would make this thing ‘inexplicable’ is if ATC had some reason to believe N600XL was at FL360 and the Mode C on the climbing B738 had reached FL370 .. all well prior (distance) to conflict proximity in radar airspace nose to nose yet only a short period of time before passing due closing speed!!
.
.. radio fail procedures may be academic in this case, and of little significance to ATC reasoning and/or decision making!!
.
.. the other issue that may be relevant is the ATC boundary proximity! Brasilia may have coordinated FL360 based on the intended level of N600XL at the boundary, Manaus may have coordinated FL390 for the B738 based on expected time to climb prior to the boundary ....
.
.. from memory (do not have the H4 with me) the distance from the Brasilia VOR to the ATC boundary was around 157nm, then another 125nm to abeam the military base that N600XL landed at! ... I might be wrong, but given the NW'ly track of N600XL, the MAC would have occured somewhere within 120nm NW of the boundary waypoint NABOL (between the mil base and the ATC boundary) .. which if the '15min prior' is correct, mode C loss occured just prior to NABOL .. stand to be corrected though
.
.. neither sector may have had initial 'trigger' prompts to consider all was not as it should be ... it depends largely where the mode C loss occured in relation to the boundary .. if you follow my reasoning ..... and by saying that I am not for one moment suggesting that an ATC error occured .....if you get my drift!!
.
Here is where it hangs indeed! ….. the plot thickens or thins as the case may be!!
.
Tis late, so I hope you all can see what I am getting at!!
S. Dumont, excellent post, but here's were it hangs:
If that is true: until 100 NM before the collision, i.e. 300 NM or 45 minutes after BRS and the planned level change ATC would have seen Legacy 600XL still being at FL370 without taking any protective action. And: knowing opposite same level traffic coming in from Manaus.
My sources (indeed I have sources) indicate (indicate is different than state) that the Legacy XPDR turned C mode off 15 minutes before the collision.
.
The odd shaped piece in this jigsaw may well be summarised in this one musing (assuming it is even remotely accurate)
XPDR turned C mode off
.
….. what Embraer Flight deck indications would result from Mode C fail??
…. 15 minutes before the collision
until 100 NM before the collision
.
.. didn’t someone earlier suggest the B738 was FL350 climbing FL390
.
.. from what I have seen of the H4 chart and the supposed information on MAC position, and the timings of loss of TXPDR (mode C apparently) … I am lead to ponder what ATC instructions were likely to have occurred, read backs that would likely have been required and perhaps received, and how they (time) correlate to the loss of Mode C??
… from the information (accurate or not) posted here I would think (logically based on normal ATC distance buffers for achieving vert in radar airspace) they could be almost coincidental …..very very interesting!!
.
…. to me the only thing that would make this thing ‘inexplicable’ is if ATC had some reason to believe N600XL was at FL360 and the Mode C on the climbing B738 had reached FL370 .. all well prior (distance) to conflict proximity in radar airspace nose to nose yet only a short period of time before passing due closing speed!!
.
.. radio fail procedures may be academic in this case, and of little significance to ATC reasoning and/or decision making!!
.
.. the other issue that may be relevant is the ATC boundary proximity! Brasilia may have coordinated FL360 based on the intended level of N600XL at the boundary, Manaus may have coordinated FL390 for the B738 based on expected time to climb prior to the boundary ....
.
.. from memory (do not have the H4 with me) the distance from the Brasilia VOR to the ATC boundary was around 157nm, then another 125nm to abeam the military base that N600XL landed at! ... I might be wrong, but given the NW'ly track of N600XL, the MAC would have occured somewhere within 120nm NW of the boundary waypoint NABOL (between the mil base and the ATC boundary) .. which if the '15min prior' is correct, mode C loss occured just prior to NABOL .. stand to be corrected though
.
.. neither sector may have had initial 'trigger' prompts to consider all was not as it should be ... it depends largely where the mode C loss occured in relation to the boundary .. if you follow my reasoning ..... and by saying that I am not for one moment suggesting that an ATC error occured .....if you get my drift!!
.
Here is where it hangs indeed! ….. the plot thickens or thins as the case may be!!
.
Tis late, so I hope you all can see what I am getting at!!
Last edited by Scurvy.D.Dog; 12th Oct 2006 at 16:27. Reason: To add the route distance from the ATC boundary (in red)
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Try that on an Oceanic Clearance (ICAO) - you are cleared as filed with an altitiude change right on your Flight Plan - you never - never - never - change altitude (lets hear from the NAT track folks) without further cleraance from ATC - (unless you loose comm - wherein you stay at the highest altitude) - so what is different about Brazil?
The main reasons for the difference are that communications difficulties are potentially part and parcel of oceanic operations, not just for an individual flight but also for all others around it, and that there is a long time period for any reaction to a comms loss to be dealt with. So it makes more sense for everyone to stay where they are at separated levels until they reach the other side as ATC may not be able to get in contact with affected traffic to move them out of the way, and the domestic agency will be primed and ready to deal with it in good time.
Domestic airspace operations are much more dynamic and the cleared area ahead of the aircraft is much smaller and has less predictability. Indeed, depending on the data transfer rules between centres, ATC may only get around 10 minutes warning of an aircraft entering it's airspace in the first place. The higher degree of interraction and flight profile changes and opportunites, better surveillance, and more immediate communcations channels makes it much easier for a NORDO aircraft adjusting to a known flight planned profile to be dealt with in this environment.
Horses for courses.
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my basic question is why TCAS did not warn anybody. Of course, we officially per the investigation do not know that yet, but if it is indeed the case, what caused it to malfunction?
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I've been discussing with other people around here and as I have listened to a different version of the story, regardless if it is right or not, I thought I should point it out, even though it contradicts my previous post a little.
This version basically claims that:
- Legacy was cleared to remain on FL370 after BRS until TERES (where on their FPL they should've climbed to FL380)
- There was a comm failure near TERES, but the Legacy proceeded according to FAA Lost Comm procedures, remained on the last cleared FL (instead of following ICAO procedures of following FPL levels).
- As the Legacy set the XPDR to 7600, the XPDR went unnoticed to STBY (aparently it wasn't fixed by the AD).
- There was a Lost Comm freq given by Brasilia, but that frequency was aparently copied wrong.
- After the MAC, Legacy pilots realized XPDR was on STBY and turned it on 7700.
This is by no means an official version. It's just a different version that I heard.
- Suposedly Contributing factors
- ALTN Comm freq being copied wrong;
- XPDR going to STBY after 7600 was set
- FAA Lost Comm procedure being executed instead of ICAO Standard (the later directs the lost comm aircraft to follow the FPL)
This version basically claims that:
- Legacy was cleared to remain on FL370 after BRS until TERES (where on their FPL they should've climbed to FL380)
- There was a comm failure near TERES, but the Legacy proceeded according to FAA Lost Comm procedures, remained on the last cleared FL (instead of following ICAO procedures of following FPL levels).
- As the Legacy set the XPDR to 7600, the XPDR went unnoticed to STBY (aparently it wasn't fixed by the AD).
- There was a Lost Comm freq given by Brasilia, but that frequency was aparently copied wrong.
- After the MAC, Legacy pilots realized XPDR was on STBY and turned it on 7700.
This is by no means an official version. It's just a different version that I heard.
- Suposedly Contributing factors
- ALTN Comm freq being copied wrong;
- XPDR going to STBY after 7600 was set
- FAA Lost Comm procedure being executed instead of ICAO Standard (the later directs the lost comm aircraft to follow the FPL)
Last edited by S. Dumont; 12th Oct 2006 at 22:56.
All right, so the transponder wasn't transponding. That is very, very unfortunate. Apparently the model/make of the transponder on board the legacy has a design flaw. And by that I do NOT mean the fact that it breaks down, as one can expect that all mechanical things go bust.
For some reason the bloody gadget can malfunction, and also not give some kind of warning that it is broken!!
If this is true, the manufacturer of this particular transponder must be feeling a bit uneasy by now, right?
What model/make of transponder is installed in the Legacy?
For some reason the bloody gadget can malfunction, and also not give some kind of warning that it is broken!!
If this is true, the manufacturer of this particular transponder must be feeling a bit uneasy by now, right?
What model/make of transponder is installed in the Legacy?
I'm in one of those moods
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.. it is probably worth noting at this point that non-standard levels are often used, particularly in radar airspace! ... this is not an unusual procedure!
.
.... the 'filed' levels must be standard for no-radio contingencies!
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.... the 'filed' levels must be standard for no-radio contingencies!
Pegase Driver
Now we are getting close to a a pausible ATC scenario.
Santos Dumont : By "lost comm " you mean LAST frequency, it makes more sense . The vast majority of comm failures toiday ( if not all ) are ears or finger trouble on a frequency change .
What is missing is the coordination level on the 738 with Brasilia. If the estimate (or the auto ACT if they have one ) was a stable level but the a/c was still climbing instead then you have it.
As I said earlier , if indeed it is true that the Legacy Xponder went on SBY on its own AGAIN and on a new set, then Honeywell and many E145 operators are going to be in sh.... very soon.
ICAO versus FAA rules , the problem is old and has no solution. There are so many FAA procedures completely at odds with ICAO that it was only a matter of time before they kill someone.
Another chain of unprobable events and Murphy's law active again.
Santos Dumont : By "lost comm " you mean LAST frequency, it makes more sense . The vast majority of comm failures toiday ( if not all ) are ears or finger trouble on a frequency change .
What is missing is the coordination level on the 738 with Brasilia. If the estimate (or the auto ACT if they have one ) was a stable level but the a/c was still climbing instead then you have it.
As I said earlier , if indeed it is true that the Legacy Xponder went on SBY on its own AGAIN and on a new set, then Honeywell and many E145 operators are going to be in sh.... very soon.
ICAO versus FAA rules , the problem is old and has no solution. There are so many FAA procedures completely at odds with ICAO that it was only a matter of time before they kill someone.
Another chain of unprobable events and Murphy's law active again.