B737 FLC CLB IN RESPONSE TO A TCASII RA OF DURING DSCNT AND SUBSEQUENTLY SIGHTED ONE OF THEIR COMPANY'S ACFT CLBING TO THE SAME ALT TO WHICH THEY WERE CLRED.

Narrative

ON VECTORS FOR APCH TO ILS RWY 28 AT PIT IN VISUAL CONDITIONS. VECTOR HDG 090 DEGS; ASSIGNED SPD 210 KTS; CLRED TO DSND TO 5000 FT. PASSING 6000 FT; WE GOT A TA AND VISUALLY SIGHTED A COMPANY AIRBUS HDG APPROX 180 DEGS AND APPARENTLY CLBING. NORMAL INITIAL ALT OUT OF PIT IS 5000 FT AND IT APPEARED THE AIRBUS WAS CLBING TO 5000 FT. AS IT BECAME APPARENT TO US THAT THE AIRBUS AND WE WOULD BE CLOSE AT 5000 FT; WE GOT AN RA. THE RA MERELY STATED 'REDUCE DSCNT.' THAT OCCURRED AT ABOUT 5700 FT. BOTTOMING OUT AT BTWN 5700 FT AND 5600 FT; I CLBED THE ACFT BACK TO 6000 FT UNTIL THE CONFLICT WAS PAT. THEN I BEGAN THE DSCNT AGAIN TO 5000 FT. AT ABOUT 5800 FT THIS TIME APCH CTLR SWITCHED US TO A NEW APCH FREQ. CAPT WAS TALKING AND I WAS FLYING. CAPT ELECTED TO SWITCH FREQS WITHOUT QUERYING THE CTLR ABOUT THE RA. THE CTLR NEVER MENTIONED THE CONFLICT AND; BY INFERENCE; FROM HIS TONE OF VOICE; HE DIDN'T NOTICE A CONFLICT. THE CLBOUT ACFT WOULD HAVE BEEN ON A DIFFERENT FREQ; SO WE DON'T KNOW IF THE ACFT AND CTLR THERE HAD A DISCUSSION ABOUT IT. THE CAPT AND I BOTH FIRMLY BELIEVE WE WERE CLRED TO 5000 FT. WE FOLLOWED OUR COMPANY'S POLICIES RELATED TO ALT AWARENESS. I WOULD NEVER SAY I COULDN'T HAVE MADE A MISTAKE; BUT I DON'T THINK SO IN THIS CASE. THAT WAS FURTHER BACKED UP BY THE INITIAL CONTACT ON THE SECOND APCH CTL FREQ AS THE CAPT RPTED DSNDING TO 5000 FT; WITHOUT ANY ADVERSE REACTION FROM THE CTLR. I AM AT A LOSS OF EXPLAIN WHY THE FIRST APCH CTLR DIDN'T SEE OR SAY SOMETHING. WHILE WE PROBABLY WOULD HAVE MISSED; IF WE HAD CONTINUED RIGHT ON DOWN TO 5000 FT; THE MISS WOULD HAVE BEEN NEAR INDEED.