EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 2, posted (12 years 6 months 2 weeks 13 hours ago) and read 2175 times:
TCAS will provide verbal "TAs" and "RAs".
TA = traffic alert; the verbal is "Traffic" with the symbology presented on the TCAS. It is simply advisory; most of the time no action is taken. It could become an RA:
RA = resolution advisory, which has several verbal commands, one of which sounds like "Climb. Climb now!" along with a graphic display of the traffic and vertical speed. In short, an RA commands a response and most 121 ops (Canada? Botswanna? don't know!) require compliance with the RA. Typically, a response is made to ATC after the avoidance maneuver. The only routine exception is on PRM approaches (MSP, Philly), in which an a/c can impede on the protection envelope of another a/c. In this case, typically only "TA" mode is selected.
Jetguy From , joined Dec 1969, posts, RR:
Reply 4, posted (12 years 6 months 2 weeks 10 hours ago) and read 2150 times:
I've got a question for EssentialPowr and any other pilot flying TCAS equipped aircraft...
How often have you personally received a "TCAS" climb or descent? I had two last week. The first one was when we were being vectored for the approach at FTY (Atlanta - Fulton County) We were in marginal VFR conditions. A yoyo in a Bonanza wasn't talking to anyone and busted Atlanta's Class B airspace. We saw him coming and started the climb just as we received the RA. We never saw the second one and have no idea what type of aircraft it was. We were flying into Knoxville and had to "get in line" to fly through an opening in a line of T-storms. We were descending out of about 15,000" - solid IFR - and, all of a sudden, there was another idiot squawking 1200 at our altitude and we got a RA to climb. Like I said, we never saw him and center had no idea who he was. They were tracking him, but I have no idea if they ever figured out who he was.
I have only had one other RA in my life, but I have heard a few called out on the radio. If I get too many more of those I think that I will simply pull the breaker on the box. After all, what you can't see can't hurt you.
FredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 7, posted (12 years 6 months 2 weeks 10 hours ago) and read 2131 times:
On 2nd thought... Technically, you could have TCAS without having a transponder of your own, although to agree on an RA you'd still need to talk through something capable of speaking Mode S transponder lingo. It would be rather daft not to have a transponder to go with it though. There are some devices for GA which will somehow passively use the return from the transponders of other aircraft without interrogating itself, although I never checked it out in detail.
No, couldn't leave it clear and simple.
I thought I was doing good trying to avoid those airport hotels... and look at me now.
Airplay From , joined Dec 1969, posts, RR:
Reply 11, posted (12 years 6 months 2 weeks 5 hours ago) and read 2102 times:
TCAS II relies on the coordination provided through the Mode S transponders when it is processing an RA against another aircraft with Mode S. Theoretically, you can still operate without this coordination but the alerts may not be as efficient. In the real world, you can't operate TCAS II without a mode S transponder. The way many systems are configured, they won't activate without the Transponder system enabled in A/C mode. It also relies on other aircraft to have a mode S or mode A/C transponder to detect traffic. TCAS cannot "see" aircraft that are not equipped with transponders.
TCAS I which only gives TAs does not need a transponder on board to work, but again it can't detect aircraft not equipped with a mode S or mode A/C transponder.
I'm not a pilot but I often participate in system certification flight tests. The one and only RA I have ever witnessed was during EGPWS testing in Arizona adjacent to an MOA. Just as we heard the warning, two "warthogs" flew by us. I was sort of surprised that a military aircraft would be equipped with a transponder compatable with TCAS.
Bjones From United States of America, joined Feb 2002, 123 posts, RR: 0
Reply 14, posted (12 years 6 months 1 week 3 hours ago) and read 2028 times:
With TCAS II you don't need the other aircraft to have Mode S for an RA to occur. Mode S is only required for their to be coordination between RAs so that both aircraft will get different commands on their TCAS. Any aircraft using mode C can result in an RA for you.
Regarding US military aircraft all of them have mode C and some do have mode S although I doubt the A-10s you saw did.