Narrative:

Aircraft was TCAS equipped and being flown by the first officer. Originally the flight had been cleared for an ILS 23L. The captain requested runway 23R for operational reasons. Clearance was maintain 4000' to clapr and cleared for approach to runway 23R. There was no mention of traffic. The TCAS was set to 10 mi scale with below selected. At approximately the marker (riber) TCAS gave a TA. The scope was checked and it displayed yellow traffic at 12 O'clock, 600'. Both pilots attempted visibility contact but were unable to pickup the traffic. An attempt was made to call tower but frequency was congested. TCAS changed from TA to RA and commanded climb. This occurred around 2600' MSL. A go around was excuted. The lost altitude observed on scope was 400' in red. Considering normal reaction time to a situation like this I feel we may have closed to within 300' vertical sep and possibly overflew aircraft (traffic) on our go around. When the tower was advised of the go around due to TCAS RA he questioned had we been advised of pipeline traffic at 2000'. I feel that TCAS averted a possible mid air due to ATC breakdown in communication. There had been no advisement of the traffic. TCAS still needs to be adjusted and evaluated further. As a result of a number of TA's that were not really a problem I found it difficult to mentally accept the RA/climb command as valid, but followed its directions.

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Original NASA ASRS Text

Title: FLC CREW OF MLG ON APCH TO IND HAD NMAC WITH SMA AT APPROX 2000' MSL.

Narrative: ACFT WAS TCAS EQUIPPED AND BEING FLOWN BY THE F/O. ORIGINALLY THE FLT HAD BEEN CLRED FOR AN ILS 23L. THE CAPT REQUESTED RWY 23R FOR OPERATIONAL REASONS. CLRNC WAS MAINTAIN 4000' TO CLAPR AND CLRED FOR APCH TO RWY 23R. THERE WAS NO MENTION OF TFC. THE TCAS WAS SET TO 10 MI SCALE WITH BELOW SELECTED. AT APPROX THE MARKER (RIBER) TCAS GAVE A TA. THE SCOPE WAS CHKED AND IT DISPLAYED YELLOW TFC AT 12 O'CLOCK, 600'. BOTH PLTS ATTEMPTED VIS CONTACT BUT WERE UNABLE TO PICKUP THE TFC. AN ATTEMPT WAS MADE TO CALL TWR BUT FREQ WAS CONGESTED. TCAS CHANGED FROM TA TO RA AND COMMANDED CLB. THIS OCCURRED AROUND 2600' MSL. A GAR WAS EXCUTED. THE LOST ALT OBSERVED ON SCOPE WAS 400' IN RED. CONSIDERING NORMAL REACTION TIME TO A SITUATION LIKE THIS I FEEL WE MAY HAVE CLOSED TO WITHIN 300' VERT SEP AND POSSIBLY OVERFLEW ACFT (TFC) ON OUR GAR. WHEN THE TWR WAS ADVISED OF THE GAR DUE TO TCAS RA HE QUESTIONED HAD WE BEEN ADVISED OF PIPELINE TFC AT 2000'. I FEEL THAT TCAS AVERTED A POSSIBLE MID AIR DUE TO ATC BREAKDOWN IN COM. THERE HAD BEEN NO ADVISEMENT OF THE TFC. TCAS STILL NEEDS TO BE ADJUSTED AND EVALUATED FURTHER. AS A RESULT OF A NUMBER OF TA'S THAT WERE NOT REALLY A PROB I FOUND IT DIFFICULT TO MENTALLY ACCEPT THE RA/CLB COMMAND AS VALID, BUT FOLLOWED ITS DIRECTIONS.

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.