Narrative:

At cruise flight at FL280 on radar vectors to tulsa, we received a TA followed seconds later by an RA on TCASII and immediately followed it as per company procedure. I immediately informed the surprised controller of our descent. By the time he understood we had descended to 27500 ft, we had already started a climb back to FL280. The other aircraft was at FL290, in cruise flight, opposite direction. Our TCASII showed the intruder 700 ft above us and descending and within about 4-5 mi. Shortly after the RA, we acquired the aircraft visually and he was not a conflict. This is the first RA I have had in the positive control area and the controller was obviously surprised and concerned that we descended without notifying him, even though our company procedures leave us no other option if the traffic is not in sight. Apparently, there was other traffic below us at the time.

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Original NASA ASRS Text

Title: FLC OF AN MLG ACR ACFT DSNDED FROM ASSIGNED CRUISE ALT IN RESPONSE TO A TCASII RA.

Narrative: AT CRUISE FLT AT FL280 ON RADAR VECTORS TO TULSA, WE RECEIVED A TA FOLLOWED SECONDS LATER BY AN RA ON TCASII AND IMMEDIATELY FOLLOWED IT AS PER COMPANY PROC. I IMMEDIATELY INFORMED THE SURPRISED CTLR OF OUR DSCNT. BY THE TIME HE UNDERSTOOD WE HAD DSNDED TO 27500 FT, WE HAD ALREADY STARTED A CLB BACK TO FL280. THE OTHER ACFT WAS AT FL290, IN CRUISE FLT, OPPOSITE DIRECTION. OUR TCASII SHOWED THE INTRUDER 700 FT ABOVE US AND DSNDING AND WITHIN ABOUT 4-5 MI. SHORTLY AFTER THE RA, WE ACQUIRED THE ACFT VISUALLY AND HE WAS NOT A CONFLICT. THIS IS THE FIRST RA I HAVE HAD IN THE PCA AND THE CTLR WAS OBVIOUSLY SURPRISED AND CONCERNED THAT WE DSNDED WITHOUT NOTIFYING HIM, EVEN THOUGH OUR COMPANY PROCS LEAVE US NO OTHER OPTION IF THE TFC IS NOT IN SIGHT. APPARENTLY, THERE WAS OTHER TFC BELOW US AT THE TIME.

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.