Narrative:

Level at 10000 ft, ATC gave TA VFR traffic at 10500 ft, 1 O'clock, approximately 8 NM. Initiated left turn when traffic popped up on TCASII. When traffic was at 5 NM and 400 ft above us on TCASII, initiated descent with TA on TCASII. When traffic was 300 ft above us and 2 NM, TCASII gave RA to descend and I initiated an evasive maneuver of turn and descent at 4000 FPM. Passing 9500 ft, traffic passed overhead at 100-200 ft indicated by RA. Never saw the traffic visually. Passenger in first class on the right side of the aircraft window seat saw an aircraft pass over us directly less than 400 ft. I personally think the traffic probably saw us and initiated a descent thinking he was on collision course. His descent coincided with ours. When we were passing 9500 ft, the TCASII indicated he was 200-100 ft above us before a clear of conflict was issued. We had to deviate from our assigned altitude. Center gave us clearance to 9000 ft when we were passing 9500 ft, the same time the traffic passed overhead. The ATC advisory saved the day because I started a turn with that and initiated a descent with a TA. The TA was given after I already started the descent. I did make an evasive maneuver with the RA. If it weren't for both the ATC advisory and TCASII we probably would have collided.

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Original NASA ASRS Text

Title: AN ACR MLG RESPONDED TO A TCASII ALERT. ARTCC SUPPLEMENTED THE TCASII ALERT WITH A DSCNT CLRNC.

Narrative: LEVEL AT 10000 FT, ATC GAVE TA VFR TFC AT 10500 FT, 1 O'CLOCK, APPROX 8 NM. INITIATED L TURN WHEN TFC POPPED UP ON TCASII. WHEN TFC WAS AT 5 NM AND 400 FT ABOVE US ON TCASII, INITIATED DSCNT WITH TA ON TCASII. WHEN TFC WAS 300 FT ABOVE US AND 2 NM, TCASII GAVE RA TO DSND AND I INITIATED AN EVASIVE MANEUVER OF TURN AND DSCNT AT 4000 FPM. PASSING 9500 FT, TFC PASSED OVERHEAD AT 100-200 FT INDICATED BY RA. NEVER SAW THE TFC VISUALLY. PAX IN FIRST CLASS ON THE R SIDE OF THE ACFT WINDOW SEAT SAW AN ACFT PASS OVER US DIRECTLY LESS THAN 400 FT. I PERSONALLY THINK THE TFC PROBABLY SAW US AND INITIATED A DSCNT THINKING HE WAS ON COLLISION COURSE. HIS DSCNT COINCIDED WITH OURS. WHEN WE WERE PASSING 9500 FT, THE TCASII INDICATED HE WAS 200-100 FT ABOVE US BEFORE A CLR OF CONFLICT WAS ISSUED. WE HAD TO DEVIATE FROM OUR ASSIGNED ALT. CTR GAVE US CLRNC TO 9000 FT WHEN WE WERE PASSING 9500 FT, THE SAME TIME THE TFC PASSED OVERHEAD. THE ATC ADVISORY SAVED THE DAY BECAUSE I STARTED A TURN WITH THAT AND INITIATED A DSCNT WITH A TA. THE TA WAS GIVEN AFTER I ALREADY STARTED THE DSCNT. I DID MAKE AN EVASIVE MANEUVER WITH THE RA. IF IT WEREN'T FOR BOTH THE ATC ADVISORY AND TCASII WE PROBABLY WOULD HAVE COLLIDED.

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.