DEN ATCT LCL CTLR CONFUSES CALL SIGNS OF AN LR35 AND C340; PUTTING THE WRONG ACFT INTO CONFLICT WITH A B737 ON FINAL APCH.

Narrative

WHILE ON AN 8 MI FINAL APCH TO RWY 35L AT DENVER INTL ARPT; THE CTL TWR OPERATOR RADIOED 'ACFT X MAKE A R TURN TO HDG 095 DEGS AND CLB TO 8000 FT.' I ACKNOWLEDGED THE CALL BY READING BACK THE INSTRUCTIONS AND USING OUR CALL SIGN; ACFT X. UPON COMPLETING THE TURN TO 095 DEGS; WE COULD NOW SEE A B737 (Y) ON APCH TO RWY 35R. WE CONTINUED THE CLB TO 8000 FT AND PASSED WITHIN 300 FT OF THE DSNDING B737. I THEN RADIOED THE CTL TWR AND REQUESTED FURTHER INSTRUCTIONS. THE TWR OPERATOR STATED THAT THE TURN AND CLB HAD BEEN FOR ANOTHER ACFT. THE TWR THEN HANDED US OFF TO APCH CTL AND WE WERE VECTORED BACK TO AN APCH AND LNDG ON RWY 35L. WE IMMEDIATELY CONTACTED THE CTL TWR AND TRACON APCH BY TELEPHONE TO DISCUSS THIS INCIDENT. THE TWR CHIEF HAD ALREADY LISTENED TO THE AUDIO TAPES OF THE 2-WAY RADIO COMS AND HAD DETERMINED THAT THE TWR CTLR HAD ERRONEOUSLY CALLED ACFT X WHEN THE INSTRUCTIONS WERE FOR ACFT Z (C340). HAD THE INSTRUCTIONS NOT BEEN GIVEN WITH A TONE OF URGENCY; I WOULD HAVE QUERIED THE TWR OPERATOR BEFORE ACKNOWLEDGING THE INSTRUCTIONS. THE INFLECTION OF VOICE INDICATED TO ME A CONFLICT OF SOME KIND THAT NEEDED IMMEDIATE ATTN WITHOUT EXPLANATION. READING BACK THE INSTRUCTIONS VERBATIM; AS THEY WERE GIVEN TO ME; ALONG WITH OUR CALL SIGN WAS A FINAL OPPORTUNITY FOR THE TWR CTLR TO REALIZE THAT THE ACFT RESPONDING WAS NOT THE ACFT THAT THE CTLR ACTUALLY INTENDED TO TURN AND CLB.