Yes, some airports now have a ground system, (hence post #4) so there are different requirements..
In regards to altitude, for TCAS II, (which all should be using)...
INCREASE DESCENT (Resolution Advisories) RAs are inhibited below 1,450 feet radio altitude while descending and 1,650 feet while climbing.
DESCEND RAs are inhibited below 1,000 feet radio altitude when descending, and below 1,200 feet radio altitude when climbing.
All RAs are inhibited below 900 feet radio altitude when descending, and below 1,100 feet radio altitude when climbing.
TCAS voice alerts are inhibited below 500 feet radio altitude.
EGPWS (Enhanced Ground Proximity Warning System), wind-shear and stall warnings will take precedence over TCAS II RAs. TCAS II will automatically switch to the TA-only mode of operation once one of the above mentioned warnings has been generated. It will remain in TA-only mode for 10 seconds after the GPWS/TAWS or wind shear warning is removed.
Last edited by FlightPathOBN; 12th May 2013 at 21:15.