TCAS in an Emergency Descent

[ISaidRightTurns]

My understanding is that it extrapolates data based on the 3A transponder, which is what we use for civilians in ATC. Is that not right? Is there a different box, antenna, whole set-up for TCAS? Where does it get its altitude information and is it accurate to the foot, 10 feet, 100 feet ??

 

[2000flyer]

No question that TCAS will occasionally miss other A/C. Regarding the original post, I have my doubts whether TCAS would give sufficient warning to targets of potential conflict when decent rates approach or exceed 10,000 fpm, as was likely the case here.

TCAS should pick up an aircraft if it's resolution presents a conflict. TCAS looks up/down something like 2500' when in "normal" Above/Below is 9900'. When it doesn't appear on the screen the TCAS determines no conflict exsist and won't show the target. However, if the aircraft is 1100 +/- your altitude and goes back and forth 1000-1100, it will appear because TCAS is seeing a climb/descend. Same holds true if it's 900' +/- your altitude. Even though it's not climbing or descending, it's still in your protected cone so it's trying to give you a head up.

I'd have to get the books out and ask some questions regarding a high rate of descent. I don't think TCAS will give you a resolution requiring you to meet or exceed your conflicts descent rate when execisive.

I've seen TCAS TA/RA when a military a/c is climbing near vertical below me, even though it leveled off 5000' below me.

Maybe Isaidrightturns can clarify, but I don't think ATC gives a rats *** if you have them on TCAS or not. I know they won't clear you to "maintain visual contact" when you only have them on TCAS.

 

[Cardinal]

Mode C for the altitude information, coming from the same encoder. Another directional antenna is installed to sort out where the replies came from after the TCAS box broadcasts a query. Same box as the transponder for most TCAS II installations, I believe. Our ghetto TCAS I setup utlizes two separate systems. It updates about every 2 seconds. One would presume that altitude accuracy is about the same as for your purposes, coded in 100 foot intervals, since that's how it's displayed.

 

[ISaidRightTurns]

No, I don't care if you see him on TCAS or not. Above FL180, I don't care if you see him at all really, because I can't use visual seperation. The only reason I do it is because I have been up there and seen someone fly over head a 1000 feet above, its a creepy feeling, even if you are seperated. And I'm required to if the targets will merge.

I can use a form of visual seperation above FL180, but the paths must be diverging by more than 135 degrees, then you can report passing and descend someone on the backside.

 

[2000flyer]

I can use a form of visual seperation above FL180, but the paths must be diverging by more than 135 degrees, then you can report passing and descend someone on the backside.

I always wondered why sometimes I get a climb/descend and other times I wouldn't!

 

[TR4A]

"we got him on TCAS."

I quess you wouldn't like "got'em on the fish finder" either.

 

[LarryinTN]

I always understood "traffic in sight" or "negative contact". Just a pet peeve.

I was starting to think that I was the only one who used the AIM phraseology.

 

[Bandit60]

or "yeah, we're lookin". Looking at what? The hot stew? I always understood "traffic in sight" or "negative contact". Just a pet peeve. Not a big deal I suppose.

Mr. I.

My pet peeve are guys that have pet peeves like this and then say "three" instead of "tree".
Lighten up

 

[TR4A]

I was starting to think that I was the only one who used the AIM phraseology.

(d) the word "Over" if required.

You don't hear this phraseology very often.

 

[Hugh Jorgan]

I'm sick to death of hearing folks respond to traffic alerts by saying "we got him on TCAS." Nobody cares. Got him visually? No? Then you haven't "got" him at all.

The hell you don't. Tell me, Mr. King$hit know-it-all, how many times when traffic has been called to you, and it DOES happen to show up on the TCAS, and you have YET to see it visually, that you relied on your eyeballs (that happen to be superior to any electronic device known to man) without once looking back down at the TCAS to help guide your visual scan to pick up that traffic? If you say never, then you are full of $hit. If you are honest and say "usually", then you have something to work with in assisting you in acquiring visual contact sooner than you would have otherwise. Oh yeah, what was it that alerted you to the traffic when it was 12 miles out to begin with? A radio? Say it isn't so. See and avoid is great. See and avoid with a little help from technology is even better. Rant complete.