Narrative:

While being radar vectored for ILS 5L at rdu we were cleared to descend to 4000 ft MSL, traffic was right to left VFR, small GA aircraft reported by ATC at 5500 ft MSL. Suddenly 5500 ft traffic made an unexpected left turn, off assigned heading. TCASII gave us an RA -- basically telling us to maintain our current rate of descent (+/- 1200 FPM). TCASII worked well.

Google
 

Original NASA ASRS Text

Title: ACR HAS CLOSE PROX WITH SMA. TCASII RA.

Narrative: WHILE BEING RADAR VECTORED FOR ILS 5L AT RDU WE WERE CLRED TO DSND TO 4000 FT MSL, TFC WAS R TO L VFR, SMALL GA ACFT RPTED BY ATC AT 5500 FT MSL. SUDDENLY 5500 FT TFC MADE AN UNEXPECTED L TURN, OFF ASSIGNED HDG. TCASII GAVE US AN RA -- BASICALLY TELLING US TO MAINTAIN OUR CURRENT RATE OF DSCNT (+/- 1200 FPM). TCASII WORKED WELL.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.