Last week while listening to liveatc.net and tuning to the KSFO tower frequency, the following situation peaked my interest. JBU1432 was on short final for 28R or L (I truly don't recall), and radioed the Tower they needed to perform a go-around. The controller on duty was quite busy, you could tell, and asked 1432 "what's the reason for the go-around", Captain or FO replied and she didn't hear him while handling other traffic... she asked him again more formally when re-directing her attention to it, and he repeated "DUE TO AN RA, M'AAM!".... You could tell he was somewhat annoyed at having to repeat the reason (they were also probably busy handling the specifics of executing the go-around). Can anybody shed light on what an 'R.A.' is and how it affects a go-around decision?? To my best research, it seems to be related to TCAS somehow...but can't find any clear info. Thanks very much. ~Alan

It's a TCAS resolution advisory. It happens when another aircraft enters your safety bubble around your own aircraft (or the other way around, but it doesn't really matter) and you're getting dangerously close to each other, eventually leading to a near miss (or more) within about 20 or 30 seconds. I don't have the exact specs in mind that will trigger it so don't hit on me if that's not really accurate (because it's probably not). Anyways, an RA kinda tells you where to go in a unmistakable manner. Could be something like "CLIMB, CLIMB" and you eventually get red areas on your ADI and VSI, depending on the aircraft you fly, that tell you where to stay away from in order to clear the conflicting traffic. Look here for an example. Plus the conflicting traffic on the TCAS display will turn into a red square symbol. As for the G/A, I'm not sure but I believe when you have an RA it usually has priority over most other things, and following the Überlingen accident back in 2002 it also supercedes any order from ATC. However, RAs are usually inhibited at low radio altitude, so he could not have been on very short final I believe. I think this is really because ATCOs will often have a very tight separation on final approach (like 2.5 NM) that would eventually trigger an RA under normal circumstances. But this is intended in rush hours and people shouldn't have to go around all the time on final, so the most you'll get below approx 1000' AGL is a traffic advisory ("TRAFFIC, TRAFFIC") and a yellow circle on your TCAS display. On a side note the phraseology to notify ATC is indeed just "TCAS RA". An active tower controller at a major intl airport (former approach radar controller) told me that's the only thing they need to know anyways, simply because they can't and shouldn't intervene during the RA. The ATCO also doesn't know about it as long as you don't tell him. Anyone with better references please join in but I hope this helps somewhat.

RA's are usually auto disabled,or selected to TA only, below 1000 feet to avoid nuisance call outs on takeoff and landing.