Air carrier X had less than standard separation from air carrier Y. System error.

Attributes
ACN	163906
Time
Date	199011
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : ozn
State Reference	FO
Altitude	msl bound lower : 33000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : czqx
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute : other oceanic enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 220 flight time total : 6045 flight time type : 1685
ASRS Report	163906
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : nmac non adherence : published procedure non adherence : required legal separation
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	vertical : 500
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

While flying from the fix whale to color via NA39, we received our oceanic clearance which changed our initial outbnd fix from 47N 50W to 46N 50W. We were level FL330 which was also our crossing altitude. Upon return to gander center frequency with confirmation of clearance, we were cleared direct 46N 50W. Our position at that time was prior to color. Gander center then queried if our transponder was being interrogated. Our reply was affirmative and gander confirmed contact. At a point beyond a position a beam of color, gander informed us that we would have to descend to FL310 due to crossing traffic. He then instructed us to descend to FL310. After we had started our descent, gander again queried if we were descending. Again we replied affirmative. Our heading was approximately 125 degree. Gander then instructed us to turn left to a heading of 070 degree for vectors. During the turning descent, I saw air carrier Y, widebody transport, at the 2 O'clock position, high, on a collision course. I disengaged the autoplt and increased the rate of descent. The other aircraft passed overhead approximately 500'. The conditions were VMC and night. We informed gander of what had occurred and leveled at FL310. Gander informed us that we were on radar and reclred us on course to 46N 50W. During the starboard turn, gander again asked if we were turning. When established on course direct, gander reclred us to FL330. The time of the incident was at position 4630N 5135W recorded immediately after the aircraft xed flight paths.

Original NASA ASRS Text

Title: ACR X HAD LESS THAN STANDARD SEPARATION FROM ACR Y. SYSTEM ERROR.

Narrative: WHILE FLYING FROM THE FIX WHALE TO COLOR VIA NA39, WE RECEIVED OUR OCEANIC CLRNC WHICH CHANGED OUR INITIAL OUTBND FIX FROM 47N 50W TO 46N 50W. WE WERE LEVEL FL330 WHICH WAS ALSO OUR XING ALT. UPON RETURN TO GANDER CTR FREQ WITH CONFIRMATION OF CLRNC, WE WERE CLRED DIRECT 46N 50W. OUR POS AT THAT TIME WAS PRIOR TO COLOR. GANDER CTR THEN QUERIED IF OUR XPONDER WAS BEING INTERROGATED. OUR REPLY WAS AFFIRMATIVE AND GANDER CONFIRMED CONTACT. AT A POINT BEYOND A POS A BEAM OF COLOR, GANDER INFORMED US THAT WE WOULD HAVE TO DSND TO FL310 DUE TO XING TFC. HE THEN INSTRUCTED US TO DSND TO FL310. AFTER WE HAD STARTED OUR DSNT, GANDER AGAIN QUERIED IF WE WERE DSNDING. AGAIN WE REPLIED AFFIRMATIVE. OUR HDG WAS APPROX 125 DEG. GANDER THEN INSTRUCTED US TO TURN L TO A HDG OF 070 DEG FOR VECTORS. DURING THE TURNING DSNT, I SAW ACR Y, WDB, AT THE 2 O'CLOCK POS, HIGH, ON A COLLISION COURSE. I DISENGAGED THE AUTOPLT AND INCREASED THE RATE OF DSNT. THE OTHER ACFT PASSED OVERHEAD APPROX 500'. THE CONDITIONS WERE VMC AND NIGHT. WE INFORMED GANDER OF WHAT HAD OCCURRED AND LEVELED AT FL310. GANDER INFORMED US THAT WE WERE ON RADAR AND RECLRED US ON COURSE TO 46N 50W. DURING THE STARBOARD TURN, GANDER AGAIN ASKED IF WE WERE TURNING. WHEN ESTABLISHED ON COURSE DIRECT, GANDER RECLRED US TO FL330. THE TIME OF THE INCIDENT WAS AT POS 4630N 5135W RECORDED IMMEDIATELY AFTER THE ACFT XED FLT PATHS.

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.