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TCAS - Easy 4DD France, today

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TCAS - Easy 4DD France, today

Old 14th Mar 2004, 01:38
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TCAS - Easy 4DD France, today

In the vague hope that the crew (Capt?) of the above flight might read this, could I just point out what a good job you did of bringing our profession into disrepute today, with your angry exchange on the radio to french ATC after your TCAS non-event.

For those who didnt hear it, the aircraft turned in response to a TA (not an RA), and when queried by ATC as to why the turn had ocurred, replied that they "had to manoevure due to a yellow TCAS".

Poor French lady was at some difficulty with non-standard language but kept trying to understand why the LATERAL manoevure had taken place even though a/c were 5 miles apart.

She also tried to point out that the turn had reduced spearation between 4DD and another a/c.

Instead she gets a torrent of angry invective from our so called professional colleague who obviously is not aware that:-

1) You dont manoeuvre in response to a TA - certainly not laterally
2)TCAS isnt accurate in azimuth anyway (I have seen a/c at 11 o'clock which TCAS 'thinks' are at 2 o'clock).

I would imagine the FO's face was doing a sterling job of imitating a radiant heater - poor chap.

And before you ask - no - I am not an "Easy-hater", they didnt turn me down for a job etc etc.

Still, your eventual insistence on filing a report should at least bring some justice - I just wonder if you are man enought to apologise. If not, I understand that Aeroflot have a vacancy on their cross-Swiss route.

Rant over

Last edited by livingdead; 14th Mar 2004 at 07:24.
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Old 14th Mar 2004, 02:52
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Apologise for sounding naive and ignorant what is 4DD?

Rwy in Sight
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Old 14th Mar 2004, 03:08
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sorry if it wasnt clear - Easy 4DD was the callsign!
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Old 14th Mar 2004, 03:22
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Shirley the crew could have at least informed my French colleagues as to what it was they were doing since it was "only" a TA they were reacting to - not waiting until after the (non) event.

I've seen replay upon replay of incidents whereby crews have taken separation into their own hands in the lateral plane (tee hee etc etc) - when given a TA by their little on-board box - often with a resultant actual loss of separation (one particularly nasty incident involving two cargo aircraft coincidentally over France springs to mind).

As livingdead rightly says TCAS doesn't work well on the lateral plane at all - you're offered a very very very distorted picture on the FD thanks to the vagries of airborne radar, moving targets and all that sort of stuff.

I'm sure when the chap / chappess files the incident it'll all come out in the wash
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Old 14th Mar 2004, 03:36
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Livingdead,

Perhaps you'd like to read the Boeing QRH for the Boeing 737.

I quote:

"Traffic Aviodance

Immediately accomplish the following recall whenever a TCAS traffic advisory (TA) or resolution advisory (RA) occurs.

<snip>

For TA:

Look for traffic using traffic display as a guide. Call out any conflicting traffic.

If traffic is sighted, maneuver as required,

For RA:

<snip>."

Boeing QRH certainly differs to you knowledge of TCAS.

Our ops manual backs this up too.

So just maybe the said Captain saw something he didn't like and therefore maneuvered as appropriate?
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Old 14th Mar 2004, 03:39
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If it was a visual sighting I suppose it's a different kettle of fish.
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Old 14th Mar 2004, 04:26
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Sure, IF it was a visual sighting. To repeat what has already been said here, TCAS is intended to assist IN THE VERTICAL PLANE ONLY as horizontal accuracy is limited, to say the least. If you guys start monoeuvering all over the place horizontally based on what you think you see on TCAS then we may as well throw away the radar and leave you to it.
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Old 14th Mar 2004, 04:29
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Scottie:
the manouvers from the QRH you've been telling us about are indeed correct,but: the FCTM says this
'Manouvers based solely on a TA may result in reduced separation and are not recommended'
As livingdead said TACS is not accurate in azymuth
Also the TCAS/ACASII (Change 7) at response to a TA says:
" Conduct a visual seach for the intruder.If succesful,maintain visual acquisition to ensure safe separation."
As we see,no manouvre.Just look out.If it won't be safe separation ,the TA will change to RA -then ,and only then you should make the TCAS demanded vertical avoiding manouvre.
We should trust the instruments ,TCAS is one of them,we have some sad examples of not doing it.
Brgds
Alex
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Old 14th Mar 2004, 05:11
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ALexban,

Well my FCTM says slightly different!

"<skip>
Look for traffic using the traffic display as an aid
Call out any conflicting traffic
Do not maneuver unless visual contact confirms that separation is not adequate.

Maneuvers based solely on a TA may result in reduced separation and are not recommended"

Sure nothing should be done on a TA when not visual, wait for the RA and follow it. But if he was visual it is a completely different story.

I'm not saying the Captain was right to do what he did, in fact I'm not commenting at all on his actions. But the QRH, FCTM and Ops manual give him the latitude to act.

Since none of us knows what really happened we'd best leave it at that eh?
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Old 14th Mar 2004, 07:23
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for info:-

In the ensuing exchange between ATC and the aircraft, they stated that they had manoeuveured BECAUSE they were IMC and had not acquired visual contact.

Further, I'm first to admit that I'm not perfect and make many a mistake and I dont have perfect recall of every technical item I have evr studied, so my real "beef" was not the fact that a manoeveur had taken place but the quite appalling way in which he tried to browbeat the French ATCO, who couldnt understand and was seeking an explanation as to whether it was normal to take avoiding action for a TA, and was trying to explain that 5nm separation had been maintained etc.

I wouldnt dare to have posted here on the subject had I not heard the comments from others who witnessed the exchange, who clearly endorsed my feelings!

Of course all this was taking up valuable RT time; if he was unhappy he should have simply stated that he was filing a report and not argued the toss on the RT

MY TCAS manual says
"Manoeuvere soley on receipt of a TA is not permitted"
MY Flight Manual says
"Manoeuveres should not be made on the basis of the traffic display alone; this display is provided solely to aid visual acquisition of intruders"

Last edited by livingdead; 14th Mar 2004 at 07:34.
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Old 14th Mar 2004, 08:29
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Argueing and/or being angry on the RTF towards ATC/pilots (depending on where you are sat) is highly unprofessional and only likely to force the receiver into pursuing paperwork more. If this Captain took the decision upon himself to provide lateral separation based on a TA then I hope he has a superb excuse otherwise I hope that EasyJet seriously repremand him (as the French Investigation Unit certainly will be chasing his tail). At the least if he was unhappy then an initial call to the controller could either a) assure him separation will be maintained; or b) alert the controller to provide neccessary avioding action. As has been said and proved, taking your own avoiding action laterally can seriously compromise a separation elsewhere. I for one am not looking forward to the new generation of TCAS that is going to provide headings as well as vertical calls when an RA is triggered, ATC avoiding action will have to become a thing of the past to try and ensure there are no contradictions that may lead to the inevitable.

By all means have queiries, but NEVER vent anger or frustrations, its all recorded and WILL come back to haunt you.....
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Old 14th Mar 2004, 10:43
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And how do you KNOW that the a/c you are visual with is the one you are getting a TCAS from? Answer - you dont.
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Old 14th Mar 2004, 11:08
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by livingdead:

If not, I understand that Aeroflot have a vacancy on their cross-Swiss route.
Presumably this is a reference to the Bassersdorf, Switzerland accident in 2002. One of the two aircraft involved was a Bashkirian Airways Tu154. Nothing to do with Aeroflot. Rather like saying that this recent radio exchange you are describing involved BA.
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Old 14th Mar 2004, 12:43
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point taken, although your analogy isnt quite that accurate in as amuch as easy was never part of BA - now had you said GO, that would have been a better example!

However, the point stands - ignore TCAS/take your own avoiding action (other than visually) at your peril.

To be fair to the crew involved, ref postings above, he did say that RT frequency was blocked at time he took "avoiding" action.
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Old 14th Mar 2004, 12:54
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Exclamation

You should not change your profile solely in response to a TA, the other aircraft may well be in an RA and coordinated against you. Avoiding action generated by TCAS RAs is in the vertical plane only, manoeuvring laterally could compromise that avoiding action.
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Old 14th Mar 2004, 13:05
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However, the point stands - ignore TCAS/take your own avoiding action (other than visually) at your peril.
Totally agree with you livingdead!
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Old 14th Mar 2004, 22:10
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It does, however, raise an interesting question. Say you are cleared to climb and you get a TA for traffic above you. You're IMC, and the TA "appears" to be on your lateral and vertical path. The frequency is busy. So what would you do?

I think of all the options I'd be tempted to level off momentarily even though this is against ATC instructions. How about you lot?

Agree with the previous posts - emotive reprimands should never be heard on frequency. Sort it out on the ground. It makes me cringe every time I hear it.
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Old 14th Mar 2004, 22:55
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Kite
Don't do it.
You are now on the slippery slope of doing your own separation.
What if the azimuth is wrong (as previously attested)?
What if the controller is actually climbing you over someone else, not yet apparent on the display (remember- not every target is displayed- in fact, very few compared to what the controller is looking at.)
What if the controller previously assessed that you would comfortably climb over this traffic, missing laterally the intruder displayed to you as the TA?
You have now levelled off.
The controller is busy elsewhere.
The (now) true intruder's pilot is from a state that still affords TCAS commands a lower priority than ATC.
Do you get where this is going? We can all think up a zillion situations, but the thing that will save anyone's arse is if everyone follows standard rules in regards TCAS ie. DON"T MANOUVRE IN RESPONSE TO TA.

Not following a standard set of rules led to Bodensee. How many times do we have to learn a lesson?
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Old 15th Mar 2004, 11:57
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If not, I understand that Aeroflot have a vacancy on their cross-Swiss route.
Not the most appropriate (or accurate) sentiment to finish with, but otherwise a topic that should be of interest and concern to pilots and ATCOs everywhere, in the light of recent events.

I'm in agreement with 5milesbaby that the pilot should receive a severe reprimand for his actions. TCAS is there to help pilots prevent a collision with another aircraft, and used properly (ie following the verbal instructions in an RA situation) it works superbly.

The TA warning is solely there to prepare pilots should the situation deteriorate to the extent that an RA is required to resolve it. Generally, there's a 15 second gap to allow the crew to try to acquire the traffic visually (if in VMC). An RA gives (or should give) BOTH pilots involved a 30 second interval to take appropriate VERTICAL avoiding action before a collision occurs. If the ATCO also realises that a loss of separation is imminent, then s/he should also provide avoiding action - best practice is to give TURNS to complement the vertical solution provided by TCAS.

So there should be no lateral avoiding action unless provided by ATC. Simple as that. A pilot taking horizontal separation into his own hands risks an airmiss with other traffic, especially in a busy terminal environment where such traffic could be on a parallel heading as little as 3 miles away.

I suspect the female controller in the EZY4DD incident went through a range of emotions after the unnecessary actions of the pilot and the unnecessary tirade that followed. Doubt, fear, and probably later on a dash of anger. I know I'd have been furious if a pilot had done that to me.

Kite - if you find yourself in such a situation and you want to reduce your climb rate to 500ft per minute, feel free. Those would be the actions of an intelligent pilot who doesn't want to get involved in a nuisance RA situation. Trained ATCOs make very few mistakes (believe it or not) and the traffic you see is probably going to pass 1000ft above you. Of course, if the frequency is busy, the ATCO may not have time to call the traffic to you. However, if at all possible, the ATCO should pass traffic and reiterate the cleared level: "c/s, maintain FLxxx upon reaching, traffic in your 1 o'clock, 12 miles, crossing right to left, 1000ft above". Pilots from certain carriers will acknowledge the traffic info - "Roger, got him on TCAS", and then, instead of levelling off at a nice gentle 500fpm, proceed to climb/descend towards the traffic at the fastest possible rate. So, 15 seconds later: "London, c/s - TCAS descent". Honestly, it happens all the time. It would be laughable if it wasn't so annoying. Do pilots get some sort of bizarre kudos for flying their aircraft into the maximum number of nuisance RA situations?

LTP


One last thing:
Presumably this is a reference to the Bassersdorf, Switzerland accident in 2002.
WHBM, presumably not. More likely to be a reference to Uberlingen, which is in Germany. The Bassersdorf accident, in 2001, involved a single Crossair aircraft in what appears to have been CFIT. See this thread.
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Old 15th Mar 2004, 14:15
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Thumbs up

Very well said LTP, could not agree with you more.

What is frightening , and keep on surprising me , especially after Ueberlingen and the Nov 2003 ICAO ammendement to TCAS procedures, is that still today apparently, there are still many diffrent SOPs in cockpits regarding ACAS procedures, and so much lack of training regarding ACAS manoeuvres.

Remember : what ever you decide :
Never manoeuvre on a TA,
Never maneuvre in the opposite direction of an RA,
In case of doubt, or of conflicting ATC clearance, always follow the RA.
These 3 things might save your life one day...

Also remember that not everyone has TCAS, not everyone has a mode S transponder, some other routes may be as little as 5 NM away from you, so what you see on your ACAS display might not be the complete picture , and as said here already many times , TCAS is very bad in azimuth .... never was made for it.
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