BEECH KINGAIR 90 FLT CREW HAS CLOSE ENCOUNTER WITH AN AIRBUS DURING SURVEY FLT VICINITY OF MSY.

Narrative

BE90 FLT CONDUCTED UNDER PRIOR APPROVAL AND COORD WITH OPS SUPVR. SURVEY FLT PARALLEL TO LAKE PONTCHARTRAIN -- 1 HR ELAPSED. E AND W PASSES APPROX 15 NM LONG AT 3300 FT MSL. 6 PASSES PREVIOUSLY FLOWN. NEW ORLEANS APCH; VERY FAMILIAR WITH OUR FLT PATH AND INTENTIONS. WBOUND PASS; N OF MSY. AIRBUS ON VISUAL APCH MSY RWY 10; CLRED TO DSND TO 2000 FT MSL; BELOW MY ACFT. BOTH ACFT ADVISED BY APCH CTL; BE90 TFC IN SIGHT. VISUALLY IDENTED THE TFC APPROX 8 NM AT 2 O'CLOCK POS; DSNDING. FLT CREW ANNOUNCED 'TFC IN SIGHT AND MAINTAIN VISUAL SEPARATION.' OBSERVED THE ACFT PASSING THROUGH MY ALT. COCKPIT DISCUSSION: 'ACFT WILL PASS UNDER OUR ACFT; MAINTAIN STRAIGHT AND LEVEL.' AIRBUS STOPPED DSCNT; INITIATED A CLB. BE90 CLBING TURN TO GIVE WAY. AIRBUS ANNOUNCED; 'ACR CLBING TO 3500 FT; TCAS ALERT RECOMMENDED CLB. COMPANY PROC TO CLB.' MSY OFFERED A 360 DEG TURN. CTLR ASKED; 'TFC IN SIGHT?' AIRBUS REPLIED; 'I HAVE HIM IN SIGHT NOW!' NO REPRIMAND FROM APCH CTL. COMMENCED OUR SURVEY FLT 3 HRS AND LANDED. TELEPHONED APCH CTL TO DISCUSS THE INCIDENT. APCH EXPLAINED THAT ACR HAD VISUAL; BUT WAS INSTRUCTED TO CLB BY TCAS. THE TCAS WARNING CAUSED AIRBUS TO CLB; WHICH RESULTED IN A COLLISION COURSE.