TCAS - Friend or Foe?

[FooFighter]

Just out of inteerst, ho wmany ATCOs get completely USELESS reports from aircraft either :
(1) asking what traffic is that they can see on their TCAS or
(2) You ask them to report visual with traffic and you get "we've got him in TCAS"?

(1) is completely opintless apart from as a way of announcing to anyone else on freq that YOU have TCAS and you;r egoing to damn well use it and (2) has yet to be approved by SRG as a method of separation.

Last time I checked TCAS was not a airborne intercept radar and the pilots in question did not fly cheap fighter jets and wear big watches (well, the latter might be true...)

Fine, so TCAS shows other traffic. Don't forget about the non-sqawkers boys... the traffic your gizmo shows may be a C172 a thousand feet below with no Mode C - but the traffic you NEED to know about is a non-squawking Tornado about to tear-**** through your windshield... that's where air traffic control came in I think...

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Foo Man Shoot

[Asda]

TCAS Friend or Foe?. Definitely a friend - anything that increases safety is a benefit. Remember TCAS is designed as a 'final defence'. We shouldn't have to have it, but everyone's glad we actually do.

Pilots, as a controller I do need to know when you've had an TCAS advisory and I definitely need to know if you've had a TCAS resolution. It may be a spurious report but even so, officially I'm not allowed to, and I'm not going to try to, stop you responding to it. But then I've been briefed that any vertical deviation from level flight should not exceed 300 feet. Is this reasonable? There have been cases of spurious TCAS reports in holding stacks setting off a ripple effect with many aircraft having to make altitude changes.

No, I'm not happy to be asked what the 'traffic' is. Mostly this is because I'm too busy to start transmitting a description of what I'm doing or why. If you think you're losing or have lost separation tell me and I'll be happy to discuss it, honest. I've had a few, and only a few, pilots ask me what the reason is for a heading or altitude change is and what their traffic is. I don't make transmissions because I like the sound of my own voice, there is always a reason. Just remember I can be looking at aircraft that are up to 100 miles away from you now but will be traffic to you soon and this is my way of pre-empting a problem in a simple and effective manner. Those few pilots I mentioned above would help me if they remembered that the world can be a lot bigger than the TCAS display in the cockpit.

[This message has been edited by Asda (edited 28 April 2000).]

[jjj]

I dont mind being asked at all. But I hate when I ask if they sight an aircraft they reply "we have them on TCAS". Absolutely useless for separatiion. Maybe a good tool for you so you know where to start looking. As a controller I think of it as my friend cause it's nice to know there is a backup in case I fvck it up.

[InspectorGadget]

TCAS is a nightmare !!

It means that you can't bull**** about the 'pop up contact in yr 12 o'clock, 2 miles' that you forgot about!!!

Normally the reply is 'Yep, been watching that for the last 20 miles!'

DOH!!!

Seriously, anything that checks my six is good news.

IG

[Hamrah]

Definitely Friend.

Having said that, I feel some elements of the pilot community must learn to use it properly. As you controllers point out, it is not approved for seperation, it can be relied on too heavily, and has a number of traps. In one case recently, I know of a case where an aircraft was advised by ATC of traffic BELOW him in the descent which may give him a TCAS warning. So he reduced his rate of descent, only to trigger a TCAS warning from the traffic ABOVE him descending to 1000ft above his cleared level. Confusion allround.

The next level of TCAS needs some sort of predicitive ability. It should be able to take the Cleared Level input from the Mode Control Panel and use that information to know when an aircraft is planned to level off.

But at the moment, it's better than nothing, having had three Real TCAS RA's over the past year.

Cheers

H

[surface wind]

I fu!ked up once. After giving avoiding action the pilot replied; "I've been watching him for the last 20NM and wondered when you were going to do something about it!!!!". Thanks mate.

[10W]

Definitely a friend. And a lot of the problems such as the "Dallas Bump" where alerts are given by traffic descending in stacks should disappear as the Version 7 software is rolled out to everyone. It will also eradicate RVSM problems with excessive TAs.

Never had it used in anger during my time on the scopes but seen plenty examples where it has been in various incidents and Airprox events.

As for the "We have him on TCAS" line, gave avoiding action to a couple of aircraft a few weeks back (one came off the assigned heading and turned to follow the STAR - doh !!) and one of the pilots replied "It's OK, we have him on ACARS." Now that version I have to see :)


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10 West
UK ATC'er
[email protected]

[Grandad Flyer]

FooFighter, well, I agree with part (2) but not part (1). As has been seen on the previous postings, very, very occasionally one of you guys may screw up.
Generally, if we see something (on TCAS or visually) that looks a little close or perhaps getting closer or looking like we may be crossing, we may ask you for details of the traffic. You see, we just like to be diplomatic. If you are busy and maybe hadn't seen that separation was going to be lost, I would think that it may be nice to get a little reminder.
Its a bit like when we say something like "do you wish us to continue on this heading" when we've passed the traffic and have been on heading for absolutely ages. I think almost every time I have asked that I get a "no, you may fly direct to....".
What would you like us to say? "Hey we think you've forgotten about us being on this heading going in the wrong direction, have you?".
If you really are convinced you won't make an error and there will never be a near miss then we will be very happy not to ask for details of the traffic. But when there is a closing speed of around 1200 mph we don't get much time to "see and avoid" and if you can give us the info we need, ie. tell us that the traffic we can see is not a threat, then it helps lower our blood pressure a little.

[Billy Doyle]

FooFighter

Your attitude sucks! Try and show some respect, especially when it comes to a safety issue such as TCAS.

Yes I've had a couple of 'useless' TA reports but Pilots are entitled to request traffic information on a TA. It may be 'useless' to you and I but to a Pilot flying at 220kts in IMC its probably quite important.

As for 'we've got him on TCAS'- of course thats what they will reply, its an obvious answer unless the guy has a good working knowledge of Mats 1 and knows he must actually see the other aircraft before we can apply reduced seperation.

Try and make some effort to understand how the other half operates, it may help you to stay cool when your next TCAS report is an RA.

[identnospeed]

TCAS - invaluable !!

As radar controllers we may not have made a mistake, but if one a/c busts its level and things start getting tasty, at least TCAS gives you a chance of not watching an incident (accident?) on your sector.
Re: level deviation on an RA, I've seen as much as 1800 feet. Alarming when you're only expecting abt 700 ft.

INS

[U R NumberOne]

I think this really is one of those aspects of aviation where there are good and bad sides for both ATC and aircrew. I was always unsure (or untrusting maybe?) of TCAS until I did a jumpseat to Greece - 'nuff said I guess! Thankfully I've never had to be rescued by TCAS, but I have been on the receiving end of lots of TA-induced questions, requests for info and in one case abuse (resulting in a request to call my supervisor :mad: ).

Before we go critising each others views though, depending on the type of airspace and services you provide in it will determine how good or bad TCAS is for you. En-route in controlled airspace, with very rigid forms of separation and greatly increasing traffic levels - an excellent back-up for the ATCOs skills. Approach and Tower where separations can be quite legally reduced - a potential nightmare. Outside controlled airspace in either phase of flight - a potential lifesaver.

The bottom line has to be if TCAS improves safety, it has to be a good thing, but what of our closest rival - the SMF (separation monitoring function). Again, OK in an en-route environment, but our Approach unit is in the process of installing it - I can see big problems with this - any other airfield units using it already?

Still unsure about TCAS? Take a look at the Flabergasted thread in ATC issues - a prime example where pilots turn into controllers when they have TCAS. Fair play to the guy in the left seat for his comments on the RT.

[This message has been edited by U R NumberOne (edited 01 May 2000).]

[Spotter]

The airfield I work at is just installing SMF too, but the place I used to work at had it up & running. It's all very well, but it only comes into play after the event. That's all very well as a management too for analysing incidents. Most of the time it's just an extra burden on management time anyway as the conflicting traffic turns out to have been VFR, or reduced separation in the vicinity of a/d. I really don't think that the times when a genuine loss of separation occurs that it would have gone unnoticed by all concerned. (especially now we have TCAS out there). My verdict is OK it does what it was designed to do. But the designers were barking up the wrong tree. Conflict alert is where they should have spent the money, to try to prevent the separation loss in the first place. Incidentally is it just NATS that is using it, or do others too?

[identnospeed]

U R No 1 - is it SMF or STCA (Short Term Conflict Alert)that is being installed at your unit or both ?

SMF just monitors the sepn between a/c and notes any loss of sepn within certain parameters (eg 2nm and/or 600ft), but no alert is given on radar.

STCA, which we get in the TC gives us the pyrotechnics when things look like they might get tight. White flashing blips when it detects a conflict which may result in a loss of sepn (based on a/c climb, descent or track profile).

The blips flash red when you have or are about to lose sepn and there is a danger of collision.

Heathrow, Gatwick and Stansted apprch (based in TC)have STCA already.

INS

[U R NumberOne]

INS,

We are getting SMF. The STCA would be more useful, either instead of or as if often the case running in parallel with the snitch. As has been mentioned in an airfield environment this sort of kit is just going to cause more problems than it will solve. Whether it be IFR against VFR or using reduced separation in the vicinity, the potential to have this thing going off every few minutes is there. I also believe the initial plan was not to block out any airspace from the SMF's view - so VFR joiners and circuit traffic on a squawk would be fair game, although I now understand some areas will be blanked out.

I appreciate the criteria for setting the thing off do constitute a significant loss of separation - but an ATCO does tend to learn from his/her mistakes and that should be enough to worry about without the issue of being invited for a chat with the watch manager or manager ATC (if the loss is a good un! http://www.pprune.org/ubb/NonCGI/eek.gif )

[captlcc]

Agree wholeheartedly with number 1! (But then I ought to working at the same unit) Mixing IFR traffic that can have a ground speed as low as 60kts on base leg with larger jets with 200kts+ off the opposite base (in strong winds) makes for an interesting time! All that these wonders of technology are going to do, once the ATCO's get "singed" a few times, is to increase the separation ie: we'll use 4 or 5 miles instead of the approved 3 and put the fast ones in the hold for longer - who win's then?

[FooFighter]

Thanks to all who responded to his thread, it seems I am not alone in having some "less than productive" experiences with TCAS. Don't get me wrong, anything that is an aid to safety is grand in my book, but I do feel that SOMETIMES (not often) it is perhaps abused - because TCAS gives crews a much better picture of the traffic environment (which has to be good), maybe a crew (or pilot, singular) may feel an advantage (jockeying for position?) can be gained? And certainly sarcastic comments like "do you KNOW where number 1 is?" and "we could have got into the gap, no problem" based on TCAS info are not very helpful (especially for traineess who are alerady working their buns off - I saw this happen to a poor guy today).

Grandad Flyer, I DO understand the other side and you make good points - 99.9% of all TCAS users do it by the book, and we all sleep a little better each night. I don't pretend to know TCAS in detail, but I know enough to be "part of a system" that works - but only as long as we're all playing the same game.

However, the one "circumstance" that I DO find galling is a common event inside our CTR: VFR traffic operating not above 2A, and IFR traffic descending to 3A. MATS1 separation standards mean that if there is going to be a confliction I must pass traffic information to both the IFR and VFR traffic (and traffic avoidance to the IFR if requested by the IFR pilot). So, in theory (yes, mistakes happen) if I say nothing about conflicting VFR traffic, it is because there IS no conflicting traffic. Bottom line, we provide vertical separation until horizontal exists. But that's the way it goes some days.

But if I've got a decent stream of inbounds, operating without the luxury of a Radar 2, the extra calls due to what I undiplomatically referred to as "useless calls" can really derail your train of thought, and cause other problems (good ole domino effect). In days before TCAS, I would not have time to get into "traffic you may see" if it's decent weather, and in these TCAS days I still don't have time to go down a "traffic you may see on TCAS" road (useful to pilots as it might be).

TCAS is definitely a friend - (along with its buddy, GPWS) - but is it the 0.1% of mis-users who are the foe? ;-)

Regards
The Foo Fighter

BTW Bill Doyle - thanks for your reasoned response. ;-) Yeah, right.