Reported loss of separation between reporter's MD11 descending to 6000 ft and another air carrier at...

Attributes
ACN	386532
Time
Date	199711
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : cvc
State Reference	FO
Altitude	msl bound lower : 6200 msl bound upper : 8000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : nrt
Operator	common carrier : air carrier
Make Model Name	MD-11
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other descent other
Route In Use	arrival other enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	386532
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 5999 vertical : 200
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Holding inbound to tokyo's narita airport at aries intersection at 8000 ft. Inbound course is 258 degrees left turns, 7 mi leg. After turning inbound we were given a clearance to continue our turn to heading 160 degrees and descend to 6000 ft. A flight below us had a previous clearance to depart aries on a heading of 160 degrees and was at 6000 ft. As we rolled out on the 160 degree heading and descended below 6500 ft, we received a TCASII TA alert and realized that the other flight was now closely in trail and tracking parallel to us. We leveled off at 6200 ft with a -200 indicated on the TA alert. The other flight was less than 1 mi to our 4-5 O'clock position. ATC was advised and the other flight was directed to turn right to a heading west of our track. The copilot could see it over his shoulder and the flight crew acknowledged seeing us. Apparently ATC misjudged the result of the 2 different clrncs given each flight. My concern is why we never got a TCASII RA alert even though we were within 200 ft altitude and less than 1 mi proximity to the other aircraft. Our TCASII had tested ok and we were getting altitude information from the other aircraft.

Original NASA ASRS Text

Title: RPTED LOSS OF SEPARATION BTWN RPTR'S MD11 DSNDING TO 6000 FT AND ANOTHER ACR AT 6000 FT.

Narrative: HOLDING INBOUND TO TOKYO'S NARITA ARPT AT ARIES INTXN AT 8000 FT. INBOUND COURSE IS 258 DEGS L TURNS, 7 MI LEG. AFTER TURNING INBOUND WE WERE GIVEN A CLRNC TO CONTINUE OUR TURN TO HDG 160 DEGS AND DSND TO 6000 FT. A FLT BELOW US HAD A PREVIOUS CLRNC TO DEPART ARIES ON A HDG OF 160 DEGS AND WAS AT 6000 FT. AS WE ROLLED OUT ON THE 160 DEG HDG AND DSNDED BELOW 6500 FT, WE RECEIVED A TCASII TA ALERT AND REALIZED THAT THE OTHER FLT WAS NOW CLOSELY IN TRAIL AND TRACKING PARALLEL TO US. WE LEVELED OFF AT 6200 FT WITH A -200 INDICATED ON THE TA ALERT. THE OTHER FLT WAS LESS THAN 1 MI TO OUR 4-5 O'CLOCK POS. ATC WAS ADVISED AND THE OTHER FLT WAS DIRECTED TO TURN R TO A HDG W OF OUR TRACK. THE COPLT COULD SEE IT OVER HIS SHOULDER AND THE FLC ACKNOWLEDGED SEEING US. APPARENTLY ATC MISJUDGED THE RESULT OF THE 2 DIFFERENT CLRNCS GIVEN EACH FLT. MY CONCERN IS WHY WE NEVER GOT A TCASII RA ALERT EVEN THOUGH WE WERE WITHIN 200 FT ALT AND LESS THAN 1 MI PROX TO THE OTHER ACFT. OUR TCASII HAD TESTED OK AND WE WERE GETTING ALT INFO FROM THE OTHER 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.

Reported loss of separation between reporter's MD11 descending to 6000 ft and another air carrier at 6000 ft.