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Loss of seperation????

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Loss of seperation????

Old 2nd Jun 2007, 17:14
  #21 (permalink)  
 
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I don't think any of the controllers are authorised to say anything about these things... I know about ppl who got into trouble for saying something like that here on pprune...
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Old 2nd Jun 2007, 18:16
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MMENCLLBAMAN sounds like he's either a passenger with an over active mind or a journalist on the sniff for a future made up feature in the 'Red Tops'.

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Old 2nd Jun 2007, 19:11
  #23 (permalink)  
 
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jackbauer
Sorry Nigel but the first rule of TCAS procedure is NOT to maneuver based on TA alone. You must wait for the RA to trigger before you do anything
Who said anything about a TA and/or RA
TCAS is a vertical aviodance tool only, as discussed above. I know of no reason or rule not to use lateral avoidance as well if I do not compromise the vertical avoidance. If, and it's a big if, the event was as dramatic as described, then the TCAS "system" had either failed, either the equipment or one or more crews. You are a better man than I if you are going to fly into another aircraft you see and tell your maker "but TCAS said nothing"
As you say, "do not manoeuvre based on TA alone". I would agree... However, a TA action (for us anyway) is to "attempt to see the reported traffic". What is the point of attempting to see the reported traffic if the subsequent drill is to fly into it A TA and/or visual sighting is not "TA alone".
So I am afraid my principles stick. TCAS is a vertical only mode, and judging / achieving vertical seperations is difficult - so let TCAS look after that. TCAS does not look after you laterally, and visually judging / achieving lateral separation is easier. If I felt genuinely threathened by traffic acquired visually, and TCAS appeared incorrect or silent, I would certainly take lateral avoiding action.
On your principle, with the Legacy v 737 midair, you are saying that if either crew saw each other, they should have just folded their arms and waited to die
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Old 2nd Jun 2007, 23:18
  #24 (permalink)  
 
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Indeed chaps, TCAS 2 is vertical gudance only. Best complied with because the information is up to date within milliseconds as opposed to atc instructions. However, the first thing we are told to do in the event fo a TA in VMC is to LOOK for the other aircraft. If spotted all future commands may be disregarded at the pilots discretion.

However, arguing against a TCAS 2 RA in the office or in court afterwards is going to need some real solid justification. Unless the TCAS 2 unit was confirmed to be playing up.

That said, who's to say MMENCLLBAMAN didn't experience one of aviations popular visual illusions.
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Old 3rd Jun 2007, 12:41
  #25 (permalink)  
 
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This was an apparent near-miss in 1965.

Of note: Eerie precursor (interaction between two aircraft, in the same locale) to AA587.
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Old 3rd Jun 2007, 13:28
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I swear I could see the crew in the flight deck at the last moment.
What a load of bo11ocks and you lot have been sucked right in.
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Old 3rd Jun 2007, 13:43
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I agree with VectorLine

Don't feed the troll....
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Old 3rd Jun 2007, 13:50
  #28 (permalink)  
 
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fish 300 metre airmiss!!!

For info to passengers.
Vertical separation in the approach phase is 1000ft.
When banked over in a turn, e.g. whilst holding, you may find yourself looking down or up at a B747 which is only 1000ft away and the illusion is created that the separation is lateral when, in fact, it is vertical.
Looks a lot more punchy than it really is.
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Old 4th Jun 2007, 04:59
  #29 (permalink)  
 
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Aircrafts limited climb capability

TCAS dos not take into account the aircraft weight, or config, so as Basil in post #16 stated TCAC will generate the resolution of climb, but the aircraft might just be unable to climb, then the secondry warning DO not climb, puts both aircraft at risk. As the time delay in "ignoring" the initial instruction.

It should be able to modify the AP FMS to initiate the climb, or descent. After all I can do an emergency descent fully automatically, if depressurised.

Lastly are there any modern aircraft that has the ability to feed SE situations to the TCAS, or must the RA be inhibited.


Its windy out
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Old 4th Jun 2007, 13:39
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Just trying to picture this and its not adding up. You'll need to correct me if I'm wrong but assumed that you were flying Cologne to Manchester on Hapag LLoyd Express as I only work in ICAO. You have to bear in mind that around London at all levels there are lots of converging routes, and 1000ft separation used at all levels, which I know looks seriously close and can worry those not used to seeing it. I'm guessing you're looking out of the RHS and seeing traffic coming toward you at between 45 and 135 degree plane, you can't see much more than 45 degs out of a window. Near London you will still be in the cruise so at the speeds you'll be travelling if you "saw the crew in the flightdeck" then I'd expect you to be dead now. TCAS would have activated over half a mile away if it actually did. With all the "knitting" that goes on in the London Upper Sector I suggest you were given a turn and descent at the same time for streaming into Manchester with a speed restriction too hence all the noise, and the turn with descent will just compound the feeling of a high velocity manouvre. I'd say the presence of an aircraft in safe close proximity was just the luck of timing.

Please correct my initial guesswork if I'm wrong and I'll try to think of any other non-life threatening possibilities as there are several more that can explain what happenned.
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Old 4th Jun 2007, 14:19
  #31 (permalink)  
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I'm FQTV SLF with PPL.

Sitting in 1A last week, enjoying view out of the window in the cruise when a jet at slightly lower level went past at 90 degrees like a bat out of hell.

I'm sure that it was 1 or 2,000 (or more) feet below, but the unexpected appearance and the relative speed could well shock anyone who travels infrequently and is not used to such events.

I wonder how many reported near misses are as a result of this... no inplication intended to the first poster on this thread.
 
Old 4th Jun 2007, 17:28
  #32 (permalink)  

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Lots! They look kinda close to us sometimes, even though we know full well from TCAS that there is 1000 separation. Good call, F3G
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Old 5th Jun 2007, 10:52
  #33 (permalink)  
 
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Last year was on a shuttle down the hill from Glasgow to Heathrow. Around the Manchester area a Shamrock passed underneath at 90degrees to us. Was standard separation but at the speed it happens, 1000 feet doesn't look like much! Was interesting to see the perspective from the air after spending all these hours watching it on radar!
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Old 5th Jun 2007, 16:21
  #34 (permalink)  
 
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Two comments.

A very long time ago, pre TCAS, on the jump seat of a 737, we were given a warning 'opposite direction traffic 12 miles 1000 Ft above you, so we all of us looked out to see if we could see it. For a very short period of time, we did see it, and we were very happy that ATC had confirmed the separation, as it went past us directly above us. The entire event ( it wasn't an incident, so I'm being careful here) was over in less than 30 seconds, given the cruise closing speeds, but it was discussed in some detail for a lot longer than 30 seconds.

Another very long time ago, due to a LGW controller suppressing the Dunsfold transponder returns, a DAN AIR 1-11 positioning from Lasham back to LGW after maintenance was put at the bottom of the TMA, effectively at 2500 Ft. At the time, we were also over Dunsfold at 2400 Ft, just below the base of the TMA. I can assure you, as we were standing my twin Com on a wing tip, we DID see the crew members in the 1-11 as they turned left for the continued approach to LGW. I never did find out if the 1-11 crew saw us, the controller at Lasham was considerably less than happy, as he was giving us a RAS at the time, and due to late detection was only able to give us about 20 seconds warning of 'opposite direction traffic at or close to your level'.

The controller filed an airmiss, and that's how we found out that LGW has supresses the Lasham transponder returns and therefore didn't see us on their scope.

Close encounters do happen.

The event in this thread might not have been as close as we first thought, or it could have been a full blown TCAS event, bear in mind that depending on the closing angle, the flight deck might not have even seen it until they got a TCAS alert, it it was closing from behind, it would have been very visible from the cabin, but not from the sharp end!
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Old 6th Jun 2007, 19:23
  #35 (permalink)  
 
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1000 feet planned vertical separation can look very close indeed, especially in a turn. However, as alluded to by Basil earlier, co-ordination and maintenance of separation during potentially conflicting climbs and descents is surely where the greatest risk lies. There is a lot of that going on around London at any given moment!
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Old 6th Jun 2007, 22:46
  #36 (permalink)  
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However, the first thing we are told to do in the event fo a TA in VMC is to LOOK for the other aircraft. If spotted all future commands may be disregarded at the pilots discretion
No longer the recommendation. Check here under "Visual acquisition - Limitations" and the Conclusion.
Bottom line - follow the RA, no exceptions.
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