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Tcas Questions  
User currently offlineMarkBoston From United States of America, joined Oct 2001, 80 posts, RR: 0
Posted (13 years 10 months 3 weeks 6 days 23 hours ago) and read 1771 times:

If the TCAS system on board an aircraft advises the pilot to take evasive action, is this "order" also transmitted to air traffic control?

Regarding the recent collision over Germany, would the Swiss air traffic controller have received information from the TCAS on both aircraft?

6 replies: All unread, jump to last
User currently offlineFrequentFlyKid From United States of America, joined Nov 2001, 1206 posts, RR: 1
Reply 1, posted (13 years 10 months 3 weeks 6 days 23 hours ago) and read 1766 times:

I was going to ask something similiar in the Tech/Ops forum, but I guess I will just further his question here.....

If two planes get close enough where TCAS has to kick in, is the system somehow linked, for lack of a better word, to the other? What I mean is will both TCAS say climb or will they intentionally differ so they don't just climb (or descend) into each other?

User currently offlineJapanguy From United States of America, joined Nov 2001, 81 posts, RR: 1
Reply 2, posted (13 years 10 months 3 weeks 6 days 23 hours ago) and read 1757 times:


The TCAS do "talk" to each other, so that they do not give the same order.

User currently offlineN79969 From , joined Dec 1969, posts, RR:
Reply 3, posted (13 years 10 months 3 weeks 6 days 23 hours ago) and read 1754 times:

The TCAS, when operating correctly, will coordinate their commands. One TCAS will tell its a/c to climb and the other TCAS will tell its a/c to descend. But they don't always work correctly. I think TCAS is only audible in cockpit and thus would be picked up on the CVR. I don't think a controller would know if a TCAS were to go off.

User currently offlineSpitfire From France, joined Feb 2001, 801 posts, RR: 6
Reply 4, posted (13 years 10 months 3 weeks 6 days 22 hours ago) and read 1743 times:

TCAS do NOT send information to ATC, only to the pilots.

Sabena ... Never to be forgotten (12 years already , what a shame !! )
User currently offlineBroke From United States of America, joined Apr 2002, 1325 posts, RR: 3
Reply 5, posted (13 years 10 months 3 weeks 6 days 22 hours ago) and read 1738 times:

The TCAS system has in its data base the service ceiling of the airplane and its registration number. If neither airplane is near its service ceiling, the system uses the registration number to decide which airplane will receive a climb indication and which one will receive a descend indication. Since the system between airplanes "talk" to each other through the transponders, each "knows" what the other's command is. It appears the system work as it should and the crew followed ATC instructions instead of the TCAS alert. ATC does not receive this information and I don't know what it would take to receive it. One of the problems, in a heavy air traffic zone, is that the screens are so cluttered with data, it makes reading the screens difficult at times.

User currently offlineBackfire From Germany, joined Oct 2006, 0 posts, RR: 0
Reply 6, posted (13 years 10 months 3 weeks 6 days 22 hours ago) and read 1731 times:

TCAS presently does not downlink to ATC. And while the next generation of ATM (enhanced surveillance, etc) is expecting to make greater use of intent data, I don't believe that TCAS orders would be downlinked -- if TCAS is going off there simply isn't the time to let ATC make a decision on evasion. That's why TCAS automatically allocates the climb/descent RA.

IMO the only exception to blindly following TCAS should be in cases where the pilot has visual contact with the conflicting traffic and decides that to follow TCAS would be less safe than to opt for an alternative manoeuvre.

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