2 MLGS ACR ACFT HAD TCASII RA'S. THE RPTING ACFT HAD AN ALERT TELLING THE ACFT TO CLB INTO A DSNDING ACFT.

Narrative

PREFLT ACTIVITIES INCLUDED A TRANSPONDER/TCASII TEST WHICH WAS NORMAL. THE FLT DEPARTED WITH THE NORMAL FLC PLUS A FLT INSTRUCTOR ON THE JUMPSEAT. THE FLT WAS LEVEL AT FL230 WHEN SOME COM PROBLEMS WITH CTR OCCURRED; MAINLY THE CTR CTLR'S RADIO TRANSMISSIONS BEING GARBLED AS WELL AS THE FLT'S TRANSMISSIONS. THE CTR CTLR STATED THE PROBLEM WAS WITH HIS EQUIP. NO TA'S WERE RECEIVED FROM CTR OR WERE TOO GARBLED TO RECEIVE. THE TRANSPONDER WAS OPERATING IN THE TA/RA MODE AND THE FLT WAS LEVEL AT FL230 WHEN THE TCASII ISSUED A TA. THE TA WAS QUICKLY CHANGED TO AN RA WHICH SAID DSND; BUT THEN CHANGED IMMEDIATELY TO A CLB; CLB. THE VERT SPD INDICATOR SHOWED A RED ARC TO A CLB RATE OF BTWN 1500 AND 2000 FPM WITH THE GREEN 'FLY TO' ARC ABOVE THIS RATE. THE ACFT WAS PLACED INTO A CLB AND ATC ADVISED OF THE RA AND ALT CHANGE. PASSING THROUGH 23200 FT THE TFC WAS SIGHTED VISUALLY. THE TFC WAS AN MLG APPROX 1000 FT ABOVE. REALIZING TCASII HAD GIVEN AN IMPROPER COMMAND; THE CLB WAS STOPPED AND THE ACFT RETURNED TO FL230. THE ALTDEV DID NOT EXCEED 23300 FT. DURING SUBSEQUENT DISCUSSION WITH CTR IT WAS LEARNED THAT THE TFC (MLG) HAD BEEN DSNDING RAPIDLY TO FL240 DUE TO TURB AND ALSO RECEIVED AN RA TO CLB. THE ACFT WERE CONVERGING ON AN ANGLE OF APPROX 45 DEGS. SUPPLEMENTAL INFORMATION FROM ACN 213445: WE HAD BOARDED THIS ACFT IN ATLANTA AND FLEW IT TO SAVANNAH. A SUCCESSFUL TEST OF THE TRANSPONDER/TCASII SYS HAD BEEN PERFORMED. CRUISING AT FL230; WE GOT A TA AURAL WHICH IMMEDIATELY CHANGED TO AN RA ALERT. BEFORE WE COULD CHANGE OUR ALT; THE RA CHANGED FROM DSND TO 'CLB; CLB.' THE FO WHO WAS FLYING THE ACFT INITIATED AN IMMEDIATE CLB AS I WAS ADVISING ATC OF OUR RA. WE WERE CLBING THROUGH FL230.2 WHEN WE THEN ESTABLISHED VISUAL CONTACT WITH OUR TFC ABOVE US. REALIZING TCASII HAD GIVEN US AN IMPROPER COMMAND; WE DSNDED BACK TO FL230. WE FOLLOWED POLICY REGARDING TCASII OPS.