Traffic!

[Fabo 213]

You shouldn't get a warning when on approach. If I'm not mistaken, (off the top of my head here) on approach TCAS switches to TA ONLY. You will see the traffic on the display but won't get any audible indications. Same goes for takeoff. These are both high workload periods of flight and having the TCAS shouting at you wouldn't be helpful..

 

No, no, no and no.

TCAS switches to TA only mode. But this has nothing to do with high/low workload or whatever. It has to do with the fact, that when you are already descending into ground, it cannot resolve conflict by telling you to fly into the ground a bit more. It turns Resolution Advisory off because there is no resolution to give.

However, Traffic Advisory stays on, and the TCAS will happily shout at you TRAFFIC TRAFFIC! if it sees fit and it will be helpful because you will know that something is happening and to watch out.

 

ATC is responsible for maintaing separation in these situations if IFR. It's also the pilot's job to maintain eyes on other aircraft in VFR.

 

Except the very reason for the existence of TCAS is to save the day when neither of this worked.

This one here, for example, might have ended badly. http://avherald.com/h?article=458921a5&opt=0

It was the responsibility of ATC to maintain separation, they did not. TCAS issued resolution advisory, crew complied, everybody went home.

 

Similarly with the VFR pilots, TCAS is not meant to protect you from the ones that look out the window and keep out the way, but from the ones that are burried in their sectionals and drifting into your way.

[Chemanuel 8]

However, Traffic Advisory stays on, and the TCAS will happily shout at you TRAFFIC TRAFFIC! if it sees fit and it will be helpful because you will know that something is happening and to watch out.

 

Exactly!, I got videos of aircrafts on approach a 380 and all of a sudden the tcas started screaming!, and the Captain blasted the approach control over not giving them warning up to the last moment. The captain saying "THAT WAS TOO LATE"...

 

Again only once in over a year I've gotten a TRAFFIC! warning and I almost have a heart attack since it was the first time I've heard it... and that was also the last. Lately I 've been cruising at 19,500 feet with about 6 more aircraft and everybody is living happily ever after

 

Chemanuel

[scandinavian13 5,192]

Similarly with the VFR pilots, TCAS is not meant to protect you from the ones that look out the window and keep out the way, but from the ones that are burried in their sectionals and drifting into your way.

 

Yep:

http://articles.washingtonpost.com/2012-05-29/local/35458034_1_private-planes-warrenton-fauquier-airport-corinne-geller

 

Other articles show their credentials. You wouldn't expect this to come of pilots of that "vintage," if you will, but sometimes experience begets complacency.

[A320FAN 370]

Nice pics ! UT2 ?

[tf51d 284]

A couple of screen shots of a near miss at 36,000 over the UK. Interestingly I didn't get a traffic warning annunciation. The crossing aircraft was about 1000 above. Great repaint by Ricardo De Luca.

 

 

You thinks that's close!! :lol:

 

[WhiteKnuckle 11]

You thinks that's close!! :lol:

 

 

That looks fairly intimate! But still no annunciation?

 

A couple more screen shots of another encounter, same flight...

 

[Hillblom86 3]

As mentioned previously TCAS works by calculating if any transponder-equipped aircraft will come "to close" to the protected volume of airspace around your aircraft. If it predicts an aircraft will do so it calculates in how long time the collision may/will occur.

Around 30 to 60 seconds before possible impact you get a TA.

Less then 30 seconds you get a RA.

I'm not hundred percent sure about the time intervals but something around those numbers.

 

This is why you can be really close without getting a TA or RA if your flying at about the same direction and speed as another aircraft, even though the ATC separation has been busted already. The time before possible collision is over a minute.

On the other side you could get a TA or even a RA but ATC separation exists all the time. Imaging you are flying leveled flight at 10' 000 feet. And a "rocket climber" gets cleared to 9' 000 feet right below you. TCAS detects the rocket climber closing fast and calculates the time for collision to be less than satisfactory and issues a TA, it may be followed by a RA if he climbs real fast.

I heard that a fighter pilot did just this when he got cleared to a level just below a commercial jet. For fun he squeezed everything he got out of the fighter jet and shot up to his assigned level. The pilots in the jet got a RA-climb and responded accordingly. They were not so happy about that and made that clear to the fighter pilot. ^_^

[scandinavian13 5,192]

On the other side you could get a TA or even a RA but ATC separation exists all the time. Imaging you are flying leveled flight at 10' 000 feet. And a "rocket climber" gets cleared to 9' 000 feet right below you. TCAS detects the rocket climber closing fast and calculates the time for collision to be less than satisfactory and issues a TA, it may be followed by a RA if he climbs real fast.

 

Yep!

 

If anyone is interested in aviation, TRACON by Paul McElroy is a well-written book. There's a sizable portion of the book that discusses some of the issues when TCAS first came into play. In fact, if I'm remembering the book correctly, it's almost the exact situation Stefan described.

[WhiteKnuckle 11]

Yep!

 

If anyone is interested in aviation, TRACON by Paul McElroy is a well-written book. There's a sizable portion of the book that discusses some of the issues when TCAS first came into play. In fact, if I'm remembering the book correctly, it's almost the exact situation Stefan described.

 

Just checked "TRACON" in iBooks store (sorry I mostly use the iPad for reading these days - eyesight deterioration with age) and got " A Plan for the future: 10 Year Strategy for the Air Traffic Control Workforce..". by David N. Spires (what a name - is this for real?). $6.99 so I might just buy it.

 

A book I would recommend which I have (hardback) but haven' read yet (only recommending since it had good reviews so I bought it) is "Jet Age" by Sam Howe Verhovek. It includes some nice historic images.

[JC75 22]

Yes the present version of tcas is dumb, it has no clue what the intentions of the other aircraft are, so it is a bit like a back seat driver in that it starts to over react to situations it gets jumpy about, like the examples given above of high rate climbs. Other one it often gets tetchy about is non mode c equipped aircraft when you are at a lower level. It can't work out what altitude they are as they not using c but just a and thus it will often give traffic warnings against them even though they may be 1000s of feet below. Another down side is it lures pilots into a false sense of security, especially pilots operating into airports outside of controlled airspace, tcas only shows transponding equipped aircraft, so anything without a transponder, will not be seen, and there an awful lot of aircraft fling around without one(or pilots who don't turn it on) watching tcas instead of looking out the window in these situations is a bad thing to be doing.

 

Many ATC radars consoles have a similar tool to tcas called stca short term conflict alert, it's just has stupid in it doesn't know what the planes are doing, so again descending plane a and climbing plane b on top of each other will often set it off...it will produce amber then red targets. More modern radars have systems now that can calculate conflicts 100s of miles off based on aircraft performance and actually what the aircraft I doing.

 

For clarification radar separation is 1000ft vertically or either 3 miles or 5 miles horizontally depending on unit and radars used. There are times when greater separation is needed(think infringers and services outside controlled airspace) but tcas isn't trying to provide radar separation it's simply a predict tool that try's to prevent collision and its using a speed time separation really rather than a physical constraint.

[WhiteKnuckle 11]

Here's a situation where I did actually get the annunciation...a bit close for comfort! (Credit to Michael Lim for the repaint)