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

Attributes
ACN	145158
Time
Date	199005
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : hyp
State Reference	CA
Altitude	msl bound lower : 34000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 220 flight time total : 12000 flight time type : 3600
ASRS Report	145158
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued new clearance flight crew : took evasive action other
Consequence	faa : reviewed incident with flight crew faa : investigated
Miss Distance	horizontal : 6000 vertical : 1000
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Proceeding direct hyp, air carrier X was in trail of air carrier Y on same routing. A second aircraft proceeding northbound at FL350, our altitude, was to pass well ahead of our aircraft; however, separation was lost for reasons unknown. The northbound air carrier Y passed in front of our aircraft from left to right. We were given a right-hand turn of approximately 30 degrees to avoid conflict. By the time this ATC instruction was issued our turn only compounded the problem, as it kept the northbound aircraft on our nose while we were in the turn. This actually brought the aircraft closer. About the time of our closest encounter we were issued instructions to descend to FL310. We began our descent and at the same time air carrier Y, a widebody transport, climbed up several hundred ft. There was never any danger of a collision as we had visibility contact at all times. I spoke with the controller later by phone. He indicated the problem began when air carrier X was late in turning to a new heading he had issued to avoid a traffic conflict.

Original NASA ASRS Text

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

Narrative: PROCEEDING DIRECT HYP, ACR X WAS IN TRAIL OF ACR Y ON SAME RTING. A SECOND ACFT PROCEEDING NBND AT FL350, OUR ALT, WAS TO PASS WELL AHEAD OF OUR ACFT; HOWEVER, SEPARATION WAS LOST FOR REASONS UNKNOWN. THE NBND ACR Y PASSED IN FRONT OF OUR ACFT FROM LEFT TO RIGHT. WE WERE GIVEN A RIGHT-HAND TURN OF APPROX 30 DEGS TO AVOID CONFLICT. BY THE TIME THIS ATC INSTRUCTION WAS ISSUED OUR TURN ONLY COMPOUNDED THE PROB, AS IT KEPT THE NBND ACFT ON OUR NOSE WHILE WE WERE IN THE TURN. THIS ACTUALLY BROUGHT THE ACFT CLOSER. ABOUT THE TIME OF OUR CLOSEST ENCOUNTER WE WERE ISSUED INSTRUCTIONS TO DSND TO FL310. WE BEGAN OUR DSNT AND AT THE SAME TIME ACR Y, A WDB, CLBED UP SEVERAL HUNDRED FT. THERE WAS NEVER ANY DANGER OF A COLLISION AS WE HAD VIS CONTACT AT ALL TIMES. I SPOKE WITH THE CTLR LATER BY PHONE. HE INDICATED THE PROB BEGAN WHEN ACR X WAS LATE IN TURNING TO A NEW HDG HE HAD ISSUED TO AVOID A TFC CONFLICT.

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.