Originally Posted by CDN ATC
Also TCAS going off and issuing an RA for "Traffic above" when tapes prove neither airplane infringed on the 1000' separation
This is an ACAS versus ACAS-II specification incompatibility. It is also a kit problem, as follows.
This is a known problem with Honeywell's TCAS 2000 V 6.4, which is not ACAS-II-compliant, and is fixed with TCAS 2000 V7, which is ACAS-II-compliant. The issue is that the RVSM altitude-measurement requirements allow some margin for error, and if the aircraft below errs allowably above its true and the aircraft above errs allowably below its true, the vertical separation is less than that required to trigger a V 6.4 RA (but not less than that required to trigger a V7 RA).
I hear rumors that it is taking longer to get away from V6.4 than originally envisaged. Anyone have data?
PBL