TCAS in an Emergency Descent

[Lead Sled]

or "yeah, we're lookin". Looking at what? The hot stew? I always understood "traffic in sight" or "negative contact". Just a pet peeve.

Along those same lines how about the guys who call "Talley Ho"? I'
m with Avbug, you've either got them with your eyeballs or you don't.

'Sled

 

[FN FAL]

Here is a question for you guys. Today I had a NWA DC9 lose pressurization over IRQ (Colliers) at FL340. The first sign I get of it is him telling me.

First, you had a DC9 lose pressurization, then they had the nerve, telling you about it first?

You had them lose the pressurization...you had them do this? Then you get mad about them telling you about what you had them do? Gawd...you guys are confusing. Is this a gay thing or am I just missing out on the new hip lingo you kids are using these days?

 

[FN FAL]

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 ??

extrapolates? sounds like the mall rat has been doing his homework.

 

[Jim]

Aircraft squawking don't always appear on TCAS...I stated that a week or so ago here on another thread, and folks tried to say it isn't so...it is so. Traffic doesn't always appear, and folks sometimes become a little too complacent.

No you said an aircraft has to equipped with a Mode S transponder to appear on TCAS. That is not true.

However, I agree aircraft do not always show up. That they do not has nothing to do with their having Mode A or C transponders instead of Mode S. Radio wave propogation is not perfect.

Man you have an ego.

 

[ISaidRightTurns]

First, you had a DC9 lose pressurization, then they had the nerve, telling you about it first?


You had them lose the pressurization...you had them do this? Then you get mad about them telling you about what you had them do? Gawd...you guys are confusing. Is this a gay thing or am I just missing out on the new hip lingo you kids are using these days?

Where the hell did that come from? Freak.

 

[avbug]

Now jimmyboy, you quoted me, and then stated that the quote showed I have an ego. I made a statement of fact, and fact is without ego. Can you dispute that fact? You cannot. Wherein then is the ego, in your own self righteous
indignation?

No you said an aircraft has to equipped with a Mode S transponder to appear on TCAS. That is not true.

In that much, you are correct...Mode C as well as mode S. However, the thrust of my comment, which you missed entirely in your response, was that often traffic doesn't appear. I've met far too many pigheaded pilots who let their gagetry do their thinking for them, especially the TCAS. The idea that it will even pick up the majority of the traffic out there is flawed. A handy tool, but a limited one, and it should be treated and thought of in that way. Lots of non-talking, non-sqawking traffic out there, and even the traffic that is squawking frequently doesn't show up.

We tend to think of the TCAS as expanding our circle of awareness...after all, isn't it amazing how much traffic it helps us spot that we would have missed, otherwise? Of course it is. Lots of traffic. Conversely, however, often it leads to complacency when we think in these terms. While it's great that the box picks up traffic, perhaps we would be better served by thinking in terms of everything it isn't seeing.

TCAS looks up/down something like 2500' when in "normal" Above/Below is 9900'.

Now that depends on the installation. Some are 2,000 up and down with 6,000 in above and below. Mine presently is two thousand up and down with eight thousand when assigned "above" and "below." Not that it really matters.

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.

Rant complete, and as always, entirely beside the point, and without significance. At least you're consistant.

At what time have I ever said I don't use the TCAS? Never. At what time have I ever said it's a useless device? Never.

What I did say is that attempting to respond to an ATC announcement of a traffic alert or traffic in general with "gottem' on TCAS" is pointless. ATC cannot base any action on weather or not you see traffic on TCAS, it doesn't help anybody out to tell them that...and you may not even be seeing the correct traffic. Therefore, keep your trap shut until you have visual contact...because for ATC purposes, and AIM purposes, and traffic avoidance in general, you haven't "got traffic" when it's on the fish finder. You've got a dot on the screen with a differential altitude readout (maybe). That's all.

Point of fact: I use TCAS all the time, and it's a regular part of my scan, inside and out. I don't spout out ignorant statements like "Got him on TCAS," however. If you'd bothered to read my comments previously, you'd understand that. Other posters did read my comments, and virtually all agreed...except you...you who spends much more time finding little ways to invent an in for a personal attack than contributing to any conversation. As I said, at least you're consistant. Not worth spit on a pig, but consistant. Play again.

 

[eddie]

I always felt that saying "have them on tcas...we're looking" let the controller know that at least we were looking in the right direction. To be followed up by "traffic in sight". oh well.

 

[TR4A]

Got'em on the Disney Channel. Roger Wilco Over and Out!

 

[Hugh Jorgan]

I don't spout out ignorant statements like "Got him on TCAS," .

There you have it folks. We're all ignorant if we don't see perfectly eye-to-eye with bukkake-breath here. I don't think anyone would agree that saying you have a contact on TCAS means you see them and are done looking to ensure separation. I bet it's great to sit next to you and watch you fester and seeth everytime you hear that call. Or is it more like seeing you puff up your chest as you are confirmed in your conviction that you sit atop a perch of knowledge and wisdom akin to that of the Dalai Lama? I think probably the latter.

virtually all agreed...except you...you who spends much more time finding little ways to invent an in for a personal attack than contributing to any conversation.

It doesn't take even the dimmest one any more time to see an "in" for a personal attack on you than you spend on your non-contributory personal attacks. I spend more time picking out toilet paper than trying to find a reason to toss a slight your way, so don't flatter yourself.

Not worth spit on a pig,

http://members.fortunecity.com/wavjunky/swl-a/admirer.wav
Good one. I'll keep it.

 

[LarryinTN]

(d) the word "Over" if required.

You don't hear this phraseology very often.

With VHF radio's it's very rarely required.

 

[TR4A]

With VHF radio's it's very rarely required.LJ-ABXQuote:
Originally Posted by Mr. Irrelevant
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.

It's in the AIM. Just pointing it out.

 

[Av8rPHX]

How ironic, was reading this thread while listening to PHX ATC, heard a guy in a small aircraft come on and say "uhh we're lookin', we got him on TCAS tho"...

 

[ISaidRightTurns]

Soooo - From what I gather from some of the actual replies,

TCAS in a normal mode only scans +/- 2k, so it wouldn't see the conflict until about 10 seconds before the a/c passes through your altitude.

Unless you have it in Up/Down mode, then it would give you about 30 seconds warning.

Is that about the jist of it?

 

[LarryinTN]

TCAS in a normal mode only scans +/- 2k, so it wouldn't see the conflict until about 10 seconds before the a/c passes through your altitude.

Unless you have it in Up/Down mode, then it would give you about 30 seconds warning.

NO! TCAS scans it's full range all of the time. The option that controls the display effects only what's displayed on the screen.

 

[Kingairrick]

See, there you go. You read through all the "mine's bigger than yours" BS, and you can learn something here...I just did. Thanks LJ!

 

[ISaidRightTurns]

So in a situation like I had, if the emergency aircraft was SB and a conflict a/c was NB, what would the resolution be? I would imagine that the emergency a/c's TCAS would be issuing an RA to reduce the rate of descent, or climb, which wouldn't really be an option. After a few updates and the descending a/c doesn't seem to be responding, will it come up with a new resolution that works in the emergency a/cs descent?


Sorry for the technical questions, just trying to get a hold of how this works.

 

[LJ45]

looking got him on TCAS

"looking for traffic got him on TCAS "I say this to save ATC the constant updates of the traffic while we look visually.

Is this not a good idea to save the constant updates and help ATC?

 

[ISaidRightTurns]

If I need it, I'll keep calling. Even pull out the ol 7110.65 "Do you have it in sight?". If one or the other says they are in the soup, I leave it alone and go to plan B. Which with me is normally plan M or N.

 

[LarryinTN]

So in a situation like I had, if the emergency aircraft was SB and a conflict a/c was NB, what would the resolution be?

That would depend on the unique geometry of the encounter. The TCAS software is biased against an altitude crossing RA but if the ROC/ROD is sufficient it will give a crossing RA.

I would imagine that the emergency a/c's TCAS would be issuing an RA to reduce the rate of descent, or climb, which wouldn't really be an option.

Why wouldn't it be an option? An extra few seconds at altitude is a lot better than a collision. If I was in a descent after losing pressurization I'd certainly follow any RA that I received. Both pilots are on oxygen.

 

[Snoopy58]

The two TCAS's will coordinate a plan of action with each other that keeps the planes apart... but that theory depends on BOTH AIRCRAFT ADHERING TO THE RA. Obvious problem: guys with an emergency descent may or may not do everything that the RA is telling them to do. What we're told as pilots is that no, the software does not have time to "realize" that one plane isn't doing what it's supposed to & then formulate an alternate plan. To avoid false alarms (like the guy zooming up to 10, while you're level at 11), the software waits until it's pretty sure that there really is a conflict, which means that you no longer have time to "see" if the other aircraft is doing its thing.

There was a crash over Europe (I think) a while back, where TCAS told the jets to do one thing (X goes up, Y goes down) but ATC had the opposite plan in mind & was giving it over the radio about the same time. Sure enough, one jet did what ATC said, the other did what TCAS said, both did the same thing, and they collided. Outcome, we're now told that TCAS takes precedence over the controllers, since you're guaranteed that both TCAS's are one the same sheet of music (they coordinate with each other over Mode S), but both aircraft may or may not be hearing the same controller, etc.

The solution to your scenario is straightforward enough, but probably not in the checklist: the emergency descent aircraft should switch his TCAS from TA/RA to TA only. This means that they don't get an RA and during the "coordination" the other jet's TCAS does what it needs to do in order to avoid the collision WITHOUT any action by the emergency aircraft. Of course, a rapid decompression isn't the ideal time for guys to be considering stuff beyond what's in their checklist, and I don't know if it's common to include "Transponder - TA only" as a step in the rapid descent checklist. It IS in our engine shutdown in flight checklist (and I understand that this is pretty common) -- if we're down to single engine performance, you don't want somebody's TCAS calculating a mutual solution that we don't have the power to give perform!

If you're screaming down with the cabin altitude horn blowing & your ears popping, wearing an O2 mask with the adrenaline flowing, and then you get a the "monitor vertical speed" RA, that's another oh %$#& moment in a day that's already going pretty crummy.