TCAS saves the day again - or not...

[FlexibleResponse]

Let's try keep this discussion on track. Please review the topic if necessary to avoid making embarrassing statements. I found some of the following links helped me.


Interesting TCAS Overview:

http://www.caasd.org/proj/tcas/


Good Site for easy navigation on TCAS (ACAS)

http://www.eurocontrol.int/acas/index.html


ICAO Annex 2 Rules of the Air

c) in the event of an RA, pilots shall:
1) respond immediately by following the RA as indicated, unless doing so would jeopardize the safety of the aeroplane;

http://www.eurocontrol.int/acas/Oper...rocedures.html


Honeywell site with links:

http://www.honeywelltcas.com/organizations.htm

[ferris]

Yet none of those links advise what to do when responding to an RA generated in response to an incorrect modeC. You seem to be under the impression that RPT aircraft will only encounter other RPT aircraft, who's transponders are checked daily, nay, every leg. I am sorry to have to warn you that in aus under the changes as of Nov 27, RPT jets will daily encounter VFR aircraft operating without clearances in classE. These VFR aircraft don't necessarily have their transponders on, have them in verified condition, or even be on the same frequency as yourself (note-see recent incident DJ737 vs C421 near CANTY nth of MEL at FL175). Now, take the same situation and have it occur at Alice Springs or some other non-radar classE, and tell me again how TCAS will help you then?

You are no longer only worried about controller stuff-ups. You now need to worry about perfectly legal VFR operations (or simply blunderers), as well.

Post all the links you like about TCAS- it doesn't do jack if the other guy doesn't have a working, accurate, switched-on transponder.

[Aus ATC]

If both aircraft had followed their respective TCAS RAs the accident would not have happened.

But

If both aircraft had complied with their respective ATC clearances the accident would not have happened either. The Russian aircraft in all probability would have passed beneath DHL.

[Philthy]

It's a bit off-topic, but since Uberlingen came up, here's some more information about TCAS in this incident from Burt Ruitenberg at the Manly Symposium (I hope I'm quoting accurately!):

In the conflict the Bashkyrian Tu 154's TCAS was the Master and the DHL's the Slave. When the Tu 154 descended in response to ATC instructions, its TCAS did not detect the fact that own-ship was non-compliant with the RA and therefore command a sense-reversal.

If, on the other hand, the DHL had been the Master it would have sensed non-compliance with the RA by the Tu 154 and would possibly have commanded a sense-reversal in the own-ship RA.

[TAY 611]

Quite simple really TCAS (RA) like GPWS Warnings mean Pilots must be disciplined to react to allow the system to work. Ignoring or delaying reactions or trying to outsmart or second guess the system on TCAS or GPWS will be at your own peril!

[AirNoServicesAustralia]

I agree with the majority of sentiment in here. In response to a TA, by all means ask the ATC or other pilot whats going on and sort something out if need be. But when you get an RA, I as an ATC will be basing my response on the assumption that both aircraft are responding as commanded by TCAS and as such I will not give any instructions that may contradict the TCAS. Too many cooks spoil the broth, and in this case a couple of TCAS units chatting to each other and working things out is more than enough cooks.

I understand Ferris, about all the limitations of TCAS, and I have had my fair share of false RA's making aircraft under my control climb or descend unneccessarily, but on balance I think with the time constraints we are talking about, and the consequences of not getting it right, I say follow the TCAS and follow it properly and swiftly.

I do not believe an airspace system should ever be designed with it as one of the safety features as it is and for the foreseeeable future will be, a net that saves the day if everything else goes wrong. But thanks to the wisdom of Smith and Anderson, we have a system that will on a regular basis rely on TCAS (and most likely in cases where noone has done anything wrong!), so we all better make sure we are all on the same page when it comes to responding always to TCAS or not. So whats it gonna be???

[ferris]

Haven't you got anything better to do on this eve of a non-muslim religious festival?

I say follow the TCAS and follow it properly and swiftly

When have I said different? I agree totally. Just that some people need reminding that TCAS is only as good as it's weakest link- which is now daily encounters with unverified, not talking, no clearance GA VFR lighties. Follow the RA by all means, but I'd be following those instructions that say "visually aquire the intruder" like never before.

"It's a safer system". Minister John Anderson. (I'd like to see Dick Smith drink a glass of water while John says it, though).