Narrative:

ATC facility: regional approach control. Location: 5 NM northwest kagle on bowie 7 arrival, arrival on the bowie 7N arrival. Approaching kagle from 5 NM to the northwest with ATC clearance to cross kagle at 11000 ft and 250 KTS. Descending through 11800 ft, received first series of TCASII event RA messages -- 'monitor vertical speed,' then 'monitor vertical speed,' then 'don't climb.' then 'don't climb,' then 'descend,' then 'descend,' then 'descend now.' the first officer followed the TCASII RA and I notified ATC of the RA event. ATC advised a following aircraft was maintaining visual separation, a B737. As we began to level off at 11000 ft, we received a second series of a TCASII RA event. On the 5 NM scale of TCASII, a red square +400 ft followed TCASII RA instructions, and I advised ATC of TCASII RA and our intentions. Exercising emergency captain's authority/authorized, I ordered first officer to break out right turn or south of course as we descended to get lateral separation and acquire visually the other aircraft. When TCASII advisory said clear of conflict, I spotted the other air carrier B737 aircraft. We rejoined arrival and climbed to return to assigned altitude, 11000 ft. I spotted B737 aircraft directly over the top of us as we began to clear the arrival stream. After second TCASII RA event series and lack of intervention by ATC I could not take the chance the other B737 aircraft didn't really have our aircraft visually. Conditions were: daytime, clear sky, unrestr visibility. Why doesn't TCASII give lateral escape instructions?

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Original NASA ASRS Text

Title: NMAC OCCUR BTWN 2 ACR ACFT WHEN A B737 IS ALLOWED A VISUAL SEPARATION ON A PRECEDING B757 BUT LOSES SIGHT OF IT ON THE BOWIE ARR AT KAGLE INTXN, TX.

Narrative: ATC FACILITY: REGIONAL APCH CTL. LOCATION: 5 NM NW KAGLE ON BOWIE 7 ARR, ARR ON THE BOWIE 7N ARR. APCHING KAGLE FROM 5 NM TO THE NW WITH ATC CLRNC TO CROSS KAGLE AT 11000 FT AND 250 KTS. DSNDING THROUGH 11800 FT, RECEIVED FIRST SERIES OF TCASII EVENT RA MESSAGES -- 'MONITOR VERT SPD,' THEN 'MONITOR VERT SPD,' THEN 'DON'T CLB.' THEN 'DON'T CLB,' THEN 'DSND,' THEN 'DSND,' THEN 'DSND NOW.' THE FO FOLLOWED THE TCASII RA AND I NOTIFIED ATC OF THE RA EVENT. ATC ADVISED A FOLLOWING ACFT WAS MAINTAINING VISUAL SEPARATION, A B737. AS WE BEGAN TO LEVEL OFF AT 11000 FT, WE RECEIVED A SECOND SERIES OF A TCASII RA EVENT. ON THE 5 NM SCALE OF TCASII, A RED SQUARE +400 FT FOLLOWED TCASII RA INSTRUCTIONS, AND I ADVISED ATC OF TCASII RA AND OUR INTENTIONS. EXERCISING EMER CAPT'S AUTH, I ORDERED FO TO BREAK OUT R TURN OR S OF COURSE AS WE DSNDED TO GET LATERAL SEPARATION AND ACQUIRE VISUALLY THE OTHER ACFT. WHEN TCASII ADVISORY SAID CLR OF CONFLICT, I SPOTTED THE OTHER ACR B737 ACFT. WE REJOINED ARR AND CLBED TO RETURN TO ASSIGNED ALT, 11000 FT. I SPOTTED B737 ACFT DIRECTLY OVER THE TOP OF US AS WE BEGAN TO CLR THE ARR STREAM. AFTER SECOND TCASII RA EVENT SERIES AND LACK OF INTERVENTION BY ATC I COULD NOT TAKE THE CHANCE THE OTHER B737 ACFT DIDN'T REALLY HAVE OUR ACFT VISUALLY. CONDITIONS WERE: DAYTIME, CLR SKY, UNRESTR VISIBILITY. WHY DOESN'T TCASII GIVE LATERAL ESCAPE INSTRUCTIONS?

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.