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British Airways flight seconds away from mid-air disaster (Not!)

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British Airways flight seconds away from mid-air disaster (Not!)

Old 11th Nov 2007, 19:07
  #41 (permalink)  
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Not sure if this has been mentioned yet or not, but, ATC have been told that they are not to issue a turn if a pilot reports a TCAS RA as it may have an impact on the effectiveness of the wing.

Surely, a turn whether instructed by ATC or at the Pilots discretion the effectiveness of the wing is still questionable. Maybe another reason jut to stick to the RA?

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Old 11th Nov 2007, 19:38
  #42 (permalink)  
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Our Airbus manuals nowhere state "Do Not Turn". They do emphasise not to Mvre based on the TA, but to use the TA to visually acquire the traffic. What's the point of visually acquiring it if you are not allowed to avoid it

In the event before/after a TA I visually acquired a threat, and time/RT traffic etc. prevented a timely ATC co-ordinated, separation I would consider a turn as required - after all, assessing/achieving visual lateral separation is relatively easy.

If an RA results, then you have to follow the vertical guidance, of course. If it became perf limiting (unlikely) then any AoB would have to be rolled off.
We need to keep an element of commonsense here... TCAS is a great aid, but we still have eyes and ailerons


Edit for spelling

Last edited by NigelOnDraft; 11th Nov 2007 at 22:30.
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Old 11th Nov 2007, 21:05
  #43 (permalink)  
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Let's get this in context.
Lots of trucks/coaches rolling up the motorway/freeway with tired drivers/low fuel.
Time to take a break.
However what we are looking at here is lots of red eye flights arriving at the same time and the same place with marginal fuel. OK for the crew but better for the bean counters.

How many people would want to board a long haul where they knew there was marginal fuel?
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Old 11th Nov 2007, 21:28
  #44 (permalink)  
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Once you've satisfied the RA vertical command, and you've either spotted the intruder visually or ascertained it's azimuth trend on the display, I don't see anything wrong with an avoidance turn.

For one thing, it will likely clear the conflict sooner so that you can resume your assigned altitude and track more quickly. In the unlikely event your manouver creates a new RA-generating conflict, the TCAS can provide resolution for multiple targets, and you'll have to comply with the second RA.

See and avoid remains basic. While the RA must be complied with first, and cannot be ignored, it is not the only tool you have.
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Old 11th Nov 2007, 22:17
  #45 (permalink)  
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Ben There -

whats to say, for instance in a busy TMA, that the traffic you think you have spotted and decide to initiate a turn to avoid is
a) the traffic that is generating the RA
or that you will not be
b) causing another RA because you are turning towards traffic that would otherwise not have been a factor?

There is a nice example on record (that happened in UK airspace) of an incident where a pilot thinking he knew better, because of his interpretation of the inherently innacurate azimuth information on TCAS, decided that he was going to be in conflict with an aircraft. The pilot initiated his own turn, without telling ATC, to position his aircraft to cross behind the 'intruder'. He then had an airprox.

The controller had set the 2 aircraft on headings which would have acheived about 12 miles separation, and then went on to concentrate on more pressing matters. He did not see the aircraft make its 'unauthorised' turn and the first he knew about it was when the pilot called an RA descent.

The controller, as is the way, was immediately suspended, subsequently cleared after investigation.

ATCOs are instructed not to pass turn instructions on receipt of an RA call from a pilot - even though they are far more aware of other traffic that may affect the aircraft in question... unless a pilot sees a clear indication of an imminent collision, he/she should restrict themself to a climb/descent. if it's really that close, then your probably too late anyways, or reacting milliseconds after the the a/c has passed the CPA.

The time you are supposed to visually acquire the intruder is on receipt on a TA, and thats when you should be preparing yourself to initiate a manoeuvre to comply with any subsequent RA... during which you should surely be watching the instruments to in sure you keep in the green zone to give yourself the best chance to ge the most separation, not looking out the window relying on reflexes which, at the closure rates involved, will be lagging behind the facts anyway!

In the unlikely event your manouver creates a new RA-generating conflict,....
not so unlikely - there is another incident, again in UK airspace, whereby multiple - more than just 2 or 3 - RA's were triggered because of the density of traffic around an aircraft that was complying with the original RA... we still have the R/T and radar replays in the training department of our unit (along with other incidents to be used as training aids).
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Old 11th Nov 2007, 22:24
  #46 (permalink)  
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Until TCAS/ACARS III becomes a reality the recommended TCAS maneuver for a RA is for vertical separation only. Or am I missing something.
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Old 11th Nov 2007, 22:37
  #47 (permalink)  
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Last couple of posts...

Lateral Mvre during an RA I think is unworkable... From my Sim training, and for real, during an RA the priority must be to follow it 100% - that takes some drills, 2 crew co-operation in aircraft handling and ATC calls.

My comments above were directed at the posts seemingly implying you cannot look out of the window and avoid - but sit there dumbly awaiting the RA TCAS might be great, but is not infallible.

Whilst TCAS is great vertically (where visual judgement is weak), eyeball lateral separation is relatively easy, and TCAS not involved in. Anyone who thinks a single turn of say 30degrees for 15 seconds will see them hit another aircraft or mountain is living at rather a high stress level

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Old 11th Nov 2007, 23:35
  #48 (permalink)  
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I have read the entire thread but am unclear if these aircraft were on reciprocal or converging tracks?

I did get quite a fright once in Eastern Europe and then became a very willing proponent of the 'one mile right offset', not possible when on radar vectors, climbing, descending etc. but otherwise not a bad idea.
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Old 12th Nov 2007, 00:14
  #49 (permalink)  
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Good points, anotherthing.

I concede you would never know to a certainty that the aircraft you were visually avoiding is the one triggering the RA in a high density environment. You can't either be sure to a certainty that the other aircraft is complying with his RA against you.

Let me be clear that I don't advocate not complying with the RA vertical command first and foremost to any other action. Once you do, though, unless you are IMC, a set of eyeballs, assuming a two-place aircraft, should be back outside looking once RA compliance is assured.

Your point about turning into other traffic is valid, too. But I'm not suggesting a sustained course alteration but a turning maneuver of short duration; one just adequate to quell the conflict, which I wouldn't think would displace course by more than a mile at most, and would not, I hope, be likely to cause loss of traffic separation if course is then quickly resumed.

I've only had a few RAs, the last one on approach to Newark 22L last year while being line checked. The trigger was a fast climbing bizjet out of Teterboro whose rate of climb on departure broke into the RA equation even though he leveled off 1,000' below as cleared. Never saw him, but I was definitely looking for him once the VSI was in the green. The check airman didn't seem to mind.

I didn't know for sure the other guy was going to level off. But I damn sure would have turned if I'd spotted him coming at me.
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Old 12th Nov 2007, 02:36
  #50 (permalink)  
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I have read the entire thread but am unclear if these aircraft were on reciprocal or converging tracks?
That's a bit thats confusing me because if the flight turned one would have to hope the crew had a visual on the other aircraft but then the idiot reporter states the SLF in the rear of the aircraft saw the other aircraft approaching.
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Old 12th Nov 2007, 09:54
  #51 (permalink)  
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This thread appears to be going in circles, yet as far as i'm concerned there isn't even an argument.

So why the last paragraph?

For me, what comes out of this thread are there are some pilots who want to interpret this scenario as never, ever turn during a TCAS event as per SOPs. There are others being a bit more pragmatic and saying while they would always follow SOPs and never, in theory, turn during an RA, they are willing to concede that TCAS will not save you 100% of the time and visual aquisition of the traffic, if possible may allow a back up plan.
I don't think it comes down to a lck of trust in ATC though standards around the world are obviously very different.

NoD's example of 30 degrees off track for 15 seconds wouldn't erode other separation by more than a half a mile. (I've seen several pilots avoid weather by more without asking first.)
And I'm not advocating that for every TA in the LTMA but I have to wonder if a visual aquisiton and turn might just save another incident like Brasil or Lake Constance.

Still what do I know, you don't believe I'm really air traffic
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Old 12th Nov 2007, 10:22
  #52 (permalink)  
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Wizz makes a good point about the difference in preference given to TCAS alerts.
The main reason the DHL disaster came about was that westerners tend to obey alerts whereas Russian pilots for example tend to be trained to obey ATC commands......thereby creating another conflict.

The whole point of separation is worthless if we are not all on the same Datum.
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Old 12th Nov 2007, 10:24
  #53 (permalink)  
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But apart from that, in general terms, there is no inherent reason why you shouldn't be turning just as long as you aren't doing so based on looking at your traffic display.

I must admit, along with others I am sure, some of what I read on here concerns me somewhat.

IF you are a genuine pilot, it concerns me that I might be unlucky enough to be flying above/below you when you respond to an RA and decide it appropriate to throw in a turn for good measure. God forbid I ever am.

Oh, and by the way, there is an inherent reason why you should not turn...

because the procedures say you don't.

How hard is that to understand?!

Well, I'm going to have to rise to that one.

Project pilot during the implementation of TCAS at a substantial UK airline as a matter of fact. I spent months studying the system and looking at historical incidents from the FAA TCAS transition Program, as well as undergoing training with avionics manufacturers, and liasing with the ATC operational training guys so that our trainees would appreciate what was going on at the other end of the radio.

What you've done is selectively quote me, and ignore the caveat in the preceding part of my post.

You keep banging on about the fact that 'the procedure' says don't turn. It may or may not, depending on the manufacturer and the operator. If it does say 'don't turn' the major factor there is likely to be performance. (Because contrary to perceived opinion, TCAS RA inhibition based on performance is pretty rough and ready, you may well not be able to achieve the RA, and turning in those circumstances isn't going to help. But you don't want to know that do you, after all, I can't possibly be a professional pilot, and can't possibly be better informed than you.)

The bottom line is this:

You have an arsenal of tools at your disposal to avoid hitting another aircraft (6 in fact). None of them are flawless. A truly professional pilot would strive to identify the relative merits of the different methods, so that he or she would appreciate the driving force behind a set of SOPs, rather than just blindly following them in a 'one size fits all' manner.

A turn for collision avoidance has a number of strengths, as well as weaknesses (some of which you have alluded too). I don't suggest that its a flawless method. I certainly don't think people should be throwing in turns willy nilly just because they think its a good idea. But I'm concerned that you seem to insist that no one else must ever consider it, just because your type at your airline has a procedure.

And I reitereate, for the avoidance of any doubt, turns must never be initiated based on the traffic display.

We're falling into the beancounters trap here folks. They don't want to spend money training you to appreciate the systems you work with. They just want to give you a single sentence SOP and would have you believe that all situations can be solved by it. God forbid you might have to exhibit some professional judgement.


2) RAs are only effective if BOTH pilots react to them,
Not so. Most RAs are quite adequate to achieve safe separation by themselves, whether the other aircraft manouevres or not. (The only substantial exception to this is where RA inhibitions are present, and both aircraft are inhibited in the same sense.) All that is required is that the other aircraft does not manouevre in the opposite direction. If you look at the alerting times, the flight path changes, and the target separation, either aircraft can generate a vertical miss in most scenarios.

None of which detracts from the virtue of the rest of your post, that I wholeheartedly agree with.

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Old 12th Nov 2007, 10:27
  #54 (permalink)  
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You posted while I was typing. Having read your last post I don't think we're that far apart.

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Old 12th Nov 2007, 10:48
  #55 (permalink)  
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Thanks very much for the input. Very much as I understand things.

The quote from me was meant to cover the very senerio you mention, one aircraft following the RA, whilst the other climbs or descends in contravention of it, possibly to follow an ATC command. Just this happened in both the DHL crash and the JAL near-miss.

The other one people seem not willing to touch is the case of mode A only. In this case you won't GET an RA. You can hit the other aircraft and will not have recieved anything more than a TA. As for "Letting ATC do its job", THEY won't have an Altitude read-out either. Thus, with an ATC on duty and an Airliner with two professtional pilots on board, seperation relies on the first-solo guy in his 152 not busting his cleared altitude.


I'm sorry this debate descended into name calling, but, as you can see many "Actual Professtional Pilots" have similar ideas to me (and some disagree, whilst backing their arguments with logical, respectful comments). Do you " Hope I never have to fly" with all of them?
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Old 12th Nov 2007, 11:40
  #56 (permalink)  
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Another poitn worthy of throwing in here is that I think some of the TCAS learning points have got a bit muddled.

There is a very valid point that the aircraft you can see may not be the one that you are getting the RA about. There was a wonderful (from a training reinforcement point of view - I'm sure the blokes shat themselves) incident back in the early days. (Bear in mind the SOPs of the day permited an RA to be disregarded based on a visual spot.)

In a nutshell: The crew had two RAs in quick succession against two different aircraft. They saw the first target as they got the RA against the second one (still unseen). They assessed the second RA as being unnecessary but elected to fly it anyway, and then had aircraft 2 flash directly overhead (i.e.no horizontal miss, TCAS generated vertical miss).

The point is, don't let a visual spot throw you off making the RA vertical manoeuvre.

Misuses of the traffic display, with folks generating their own turns based on it - sometimes way in advance of an RA, and sometimes even turning safe separation into an RA - have a colourful past.

I would argue that if you can see something at constant relative bearing and its getting bigger, then it doesn't matter if its the traffic causing the RA or not; its a collision risk.

Lets also throw in Anotherthings observation:

ATCOs are instructed not to pass turn instructions on receipt of an RA call from a pilot
Yes (though it wasn't always that way). But even so, you'd probably be giving avoiding action up until getting a 'tcas descent (or whatever)' call.

Lets throw in an example. Vectoring in towards a regional airfield, a grobbly day with a fair bit of low level cloud. Lets say 20 miles out, in level flight. Controller suddenly says something like "Callsign! Avoiding action! Turn right heading 090 - pop up traffic from low level". As you thumb the a/p disconnect and start your turn, your TCAS gets about halfway through saying 'Traffic' and then says "Maintain vertical speed - maintain" with a red sector above your current vertical speed (i.e. saying don't climb). What do you do? Surely we'd all maintain the current altitude and fly the turn. Wouldn't we?

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Old 13th Nov 2007, 00:34
  #57 (permalink)  
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Must say I am little scared after reading this thread.

Too many pilots think they allmost have "a radar" in their aircraft these days.
TCAS is a great last option tool...but really also give us ATCO's a LOT of grey hairs too because it's used/misused like a radar by many pilots.

TCAS is not a radar, for sure it shows you about which direction to look for traffic...HOWEVER...it doNOT show you which direction the traffic is moving!!
SO..turning in a RA situation...or even worse..turning to avoid a RA...is not the smart thing to do.

Give you an example...(out of memory from a incident I did read about some time ago).
Pilot see a target on his TCAS approaching him at same level from his 10 o'clock, for the pilot it looks like the traffic is heading direct for him. So with his smart thinking he turns right without telling ATC...to avoid any TCAS RA...result was...yes you guessed correct, a near miss and RA

What the pilot ofcourse couldnt't see on his TCAS was that the target was crossing in front of him with 5nm minimum sep. from left to right about 90degrees on his flightpath. So if he had stayed on course he would had seen the target approach him..then do a arcing movement around him from left to right..and leave behind at his 4 o'clock.

TCAS is NOT the same as RADAR, it do only show direction to target, not which way he is flying...so until TCAS has been improved and works both vertically and horisontally...PLEASE..do not turn according to TCAS RA only!!!


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Old 13th Nov 2007, 14:44
  #58 (permalink)  
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The crew concerned had a turn instruction from ATC followed closely by the RA which explains why they were turning at the time.
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Old 14th Nov 2007, 21:04
  #59 (permalink)  
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Probably some of us haven't seen this:

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Old 17th Nov 2007, 11:08
  #60 (permalink)  
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Now I'm not an airline pilot, and my aircraft doesn't have TCAS - I wish it did, but that's the defence budget for you.
But to me, all that those examples from Eurocontrol demonstrate is that the aircrew did not understand the sole condition for a collision, which is that the target is closing on a constant bearing. This is, incidentally, why see-and-avoid is a poor answer in VMC. The target that's going to hit you is stationary in your field of view (if its in your field of view at all), and evolution has equipped us with a visual system that responds best to movement (it picks up the twitching grass as the sabre-toothed tiger crawls up on you). Change any part of the dynamics and the collision is avoided. For well-thought-out reasons, TCAS uses the vertical as the avoidance dynamic. But on any contact, if the bearing is changing towards the 12 o'clock, the target will pass ahead, and if the bearing is changing towards the 6 o'clock, the target will pass behind.
Sorry if I'm teaching granny to suck eggs.
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