Narrative:

Was on a flight from fll to bwi descending on nottingham 2 arrival into bwi. Passing through 20000 ft, ZDC advised us that we were to cross sabbi intersection at 15000 ft with no speed restriction. 45 seconds later center said to cross sabbi at 15000 ft and 250 KTS. 15 seconds they advised us to contact washington approach on 128.85. After trying to raise approach 2 times on 128.85, without success, returned to center frequency. They informed us that the frequency should have been 128.35. Upon switching to the new frequency, washington approach immediately said to stop our descent at 16000 ft and turn left 90 degrees. At this time we were 15950 ft, descending at 1000 FPM. Having stopped the descent at 15900 ft, the TCASII advised we had traffic off the right side approximately 3 mi and closing, 300 below us and was also descending. The TCASII advised a 900 ft climb, we climbed to 16500 ft before the advisory stopped. We never saw the other traffic, but when I got on the ground at bwi I talked to the other captain of the conflicting airplane. He said that approach advised him to turn right and increase his rate of descent to 15000 ft. He also advised me that he saw me visually turning to his left and climbing. The controller on washington approach was talking to 8- 9 aircraft when we came on his frequency. As far as I can figure out, both aircraft were cleared to sabbi at 15000 ft. Indication was that we were overtaking the other aircraft and the spacing became too close. We were never advised about the other aircraft until we got the TCASII alert. Because of the wrong frequency and the time it took to correct it, plus the approach controller having to work that great number of airplanes, all contributed to the closeness of both aircraft.

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Original NASA ASRS Text

Title: ACR HAS CLOSE PROX WITH MLG ON ARR INTO BWI. TCASII RA.

Narrative: WAS ON A FLT FROM FLL TO BWI DSNDING ON NOTTINGHAM 2 ARR INTO BWI. PASSING THROUGH 20000 FT, ZDC ADVISED US THAT WE WERE TO CROSS SABBI INTXN AT 15000 FT WITH NO SPD RESTRICTION. 45 SECONDS LATER CENTER SAID TO CROSS SABBI AT 15000 FT AND 250 KTS. 15 SECONDS THEY ADVISED US TO CONTACT WASHINGTON APCH ON 128.85. AFTER TRYING TO RAISE APCH 2 TIMES ON 128.85, WITHOUT SUCCESS, RETURNED TO CENTER FREQ. THEY INFORMED US THAT THE FREQ SHOULD HAVE BEEN 128.35. UPON SWITCHING TO THE NEW FREQ, WASHINGTON APCH IMMEDIATELY SAID TO STOP OUR DSCNT AT 16000 FT AND TURN L 90 DEGS. AT THIS TIME WE WERE 15950 FT, DSNDING AT 1000 FPM. HAVING STOPPED THE DSCNT AT 15900 FT, THE TCASII ADVISED WE HAD TFC OFF THE R SIDE APPROX 3 MI AND CLOSING, 300 BELOW US AND WAS ALSO DSNDING. THE TCASII ADVISED A 900 FT CLB, WE CLBED TO 16500 FT BEFORE THE ADVISORY STOPPED. WE NEVER SAW THE OTHER TFC, BUT WHEN I GOT ON THE GND AT BWI I TALKED TO THE OTHER CAPT OF THE CONFLICTING AIRPLANE. HE SAID THAT APCH ADVISED HIM TO TURN R AND INCREASE HIS RATE OF DSCNT TO 15000 FT. HE ALSO ADVISED ME THAT HE SAW ME VISUALLY TURNING TO HIS L AND CLBING. THE CTLR ON WASHINGTON APCH WAS TALKING TO 8- 9 ACFT WHEN WE CAME ON HIS FREQ. AS FAR AS I CAN FIGURE OUT, BOTH ACFT WERE CLRED TO SABBI AT 15000 FT. INDICATION WAS THAT WE WERE OVERTAKING THE OTHER ACFT AND THE SPACING BECAME TOO CLOSE. WE WERE NEVER ADVISED ABOUT THE OTHER ACFT UNTIL WE GOT THE TCASII ALERT. BECAUSE OF THE WRONG FREQ AND THE TIME IT TOOK TO CORRECT IT, PLUS THE APCH CTLR HAVING TO WORK THAT GREAT NUMBER OF AIRPLANES, ALL CONTRIBUTED TO THE CLOSENESS OF BOTH ACFT.

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.