Buster,

I believe that the accuracy of cuurent TCAS is not good enough to issue a heading for collision avoidance, but is certainly good enough, based on mode C, to tell you whether to climb or descend.

Also, as I have read from a study done in the 80's, I believe, turning away actually increases the chance of a collision over simply climbing or descending wings level, because the wings suddenly take up more area vertically as the A/C banks in an attempt to turn away.

Jeez,

They might be able to assemble a decent television, but it sounds as though they are about 30 years behind in the Flight Safety department. Prosecute first, investigate later. Wow, what a concept! Perhaps all captains should be provided with a knife so they can do the honourable thing after an in flight-incident.
Me thinks,not the place you'd want to do this job. :cool:

Avoidance Manoeuvres
 

OK, let's start from the beginning!

Separation between aircraft operating for commercial air transport is, for the most part, arranged by the air traffic service provider. Generally, this works pretty well, but separation can break down either when an incorrect instruction is given or when a pilot fails to comply, eg through misunderstanding or a self-generated manoeuvre.

It follows that the last thing a pilot should do - unless he has visually sighted a conflicting aircraft and has absolutely no doubt whatsoever that if he/she does nothing a collision will result - is to initiate a climb, descent or turn. If the pilot does this, separation may well be eroded with a third aircraft, and of course the controller's tactical plan will have been upset.

Even the latest version of TCAS II (Version 7) cannot display accurately the relative position of a proximate aircraft in the horizontal plane, so pilots are still instructed not to initiate turn manoeuvres on the basis of what the TCAS display shows them.

Since its introduction, TCAS II has worked well: the modern version is extremely reliable and - to the best of my knowledge - all reported 'compatible' events (where a 'climb' advisory is posted to one crew and a 'descend' advisory to the other) have been exactly as programmed to provide the maximum vertical margin as the aircraft pass their 'closest point of approach'. The algorithms in TCAS II Version 7 have removed many of the 'nuisance' alerts that were evident in earlier versions. What really matters is that pilots should all be trained to the same rules - as described in my earlier post.

TCAS III, that included horizontal advisories, never quite got past the 'breadboard' stage. Thanks to the FAA, I was able to 'fly' this trials version in one of their B727s (many years ago), and it worked impressively well during encounter scenarios, but certification of this product was a long way off. The historical record of TCAS II shows that it works so well (though of course it isn't perfect) that there simply is no case for requiring aircraft operators to pay for a TCAS III.

Also, it often happens that ATC like to achieve separation by requiring one aeroplane to change altitude/flight level when there is plenty of time before both conflicting aircraft get near to one another, but to require a change of heading when time to 'closest point of approach' is short, which is when TCAS II Resolution Advisories may be posted. In such circumstances (ATC turn instruction, TCAS II climb/descend advisory) there is no conflict between the two and so a pilot can execute both simultaneously.

Except for the fact that TCAS procedures require the pilot to level the wings and execute the climb/descent!

Turning in the maneuvre will decrease your max climbrate (though it will increase descentrate) and the G-forces required to turn and pull the nose up will make the maneuvre uncomfortable and possible dangerous for the cabin. Also, systems where the RA requirement is displayed on the EADI (horizon) are based on wings level.

So a turn and TCAS are actually in conflict with each other procedure-wise.

Thanks for explaining that guys. I'll just stay on the ground here then & pass the loadsheets on to you guys, if that's okay???:ooh: :ooh: ;)

Maybe it's about time that areas which mandate the carriage of TCAS, also make it compulsory to obery a TCAS RA ahead of any contradictory ATC instruction. Then these incidents/accidents would not occur.

It beggars belief that some pilots are still manoeuvring in direct contradiction to their TCAS RA (this JAL incident, the crash over Germany). How many more people need to die before this gets sorted out??? :*

Apparently more pilots than you think!!!!
 

There was a heap of discussion about this sort of thing here
recently.
Very sad that this still isn't crystal clear :hmm:

Sorry to show my lack of experience but from what I have been taught so far if everyone always followed TCAS and ignored ATC instructions then the a/c is safer than vice versa.

Surely if the TCAS is not reliable enough that we still need to interpret its RA and TAs then it is just giving us confusing information at a time when we should have absolute clarity.

I mean if that is the case then aren't we better of without it.

Are there any examples of accidents that have been caused by following the TCAS?

If there aren't any then surely if it says tfc tfc climb climb I'd have thought that climbing might get me out of the problem.

Whilst I did see threads that suggest you may want to do otherwise if you can positively visually seee the conflicting tfc this does not take into account the full chain.

What if there are three ac involved. You could be in the situation where thinking you can see the conflicting traffic and actaully seeing the third a/c.

Not saying that computers are infallible but they are unlikely to make this mistake and we are. So isn't this why we have TCAS?

VT

Does anyone know if the report is available in english on the web?

You have got to be kidding, right? It's not even available in Japanese.

Look, the J's are secretive about everything. The official report will read like a Readers Digest article when it is published.

I was working there at the time. The CA did screw up royally, and we got all kinds of TCAS memoes afterwards. Put this to rest. In Japan, it's a crime to violate a reg, period. They had two years to study the incident for safety sake. Now, it's time to prosecute. The end.

FlyMD I'm kinda with you on this, but more specifically I am amazed that the trainee is facing charges. Certainly within Maastricht trainees work without a license of their own, they work using the license of their coach at the time. Therefore all responsibility for the safety of air navigation lies with the coach. While training a student a couple of years ago, we had a situation leading to a loss of separation (4.7NM) and, quite rightly the ensuing investigation was centred, from an ATC perspective at least, around me as coach. I can't see under what grounds the Japanese authorities can hold the trainee responsible.

Mind you, I can't see that there was any criminal negligence here anyway. Poor controlling, yes, but criminal? As far as the TCAS/ATC discussion is concerned, I was under the impression, (please correct me if I am wrong, for I often am) that different operating agencies had different guidelines for this, which was a factor in the Swiss mid-air.