Originally Posted by pilotho
after long study i have finally found out what TA/RA stands for, although i have still got a question.
why is there an option to only have TA or RA respectivly when surely TA/RA should be selected all the time.
The only option I'm aware of is TA/RA or TA.
TA/RA is the normal operating mode and provides Traffic Advisories and Resolution Advisories.
TA provides Traffic Advisories only; no Resolution Advisories are issued. This mode prevents TCAS from issuing RAs when the aircraft is intentionally flying close to another aircraft such as closely spaced parallel approaches.
At Radio Altitudes less than 900 ft AGL descending or less than 1,200 ft AGL climbing, TCAS will be silent below these inhibit altitudes and is in TA ONLY mode. No RAs will be displayed, TAs will be displayed on the VSI/TRA but no "TRAFFIC - TRAFFIC" message will be heard. If an RA is active when the aircraft passes into the inhibited radio altitude, the RA (red square) will transition to a TA (amber circle) any red or green arcs displayed will be removed, no "CLEAR OF CONFLICT" message will be announced.