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

Attributes
ACN	178086
Time
Date	199105
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : sea
State Reference	WA
Altitude	msl bound lower : 5000 msl bound upper : 6000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sea
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 14
ASRS Report	178086
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : clearance non adherence : published procedure non adherence : required legal separation
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 16800 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was vectoring air carrier X 25 mi southwest of sea for an ILS approach to sea. I was also vectoring air carrier Y from the southeast to follow air carrier X. Air carrier Z came on my frequency and reported sea in sight. I turned air carrier Z to the east to see traffic planning a visual approach to runway 34L. At this time I asked air carrier X (but I was looking at and thinking air carrier Z) if he saw the traffic for the right runway. Air carrier X said no and that they did not have the runway at sea either. I then turned air carrier X (still thinking air carrier Z) to a right turn heading 160. This placed air carrier X in conflict with air carrier Y. I realized my error and attempted to separate air carrier X and air carrier Y. Air carrier Y refused to take one of my instructions because they were getting an onboard TCAS alarm. I recall waiting forever for each radar sweep to update because one aircraft was in coast so I could give additional instructions. The aircraft separated and landed normal. A review by both pilots and myself as we listen to the tape might be helpful, since air carrier Y had information I did not (TCAS). Similar call signs might have contributed. Callback conversation with reporter revealed the following information: the reporter stated both aircraft had gone into coast status. Air carrier Y refused a descent clearance because of a TCASII traffic alert not a resolution alert. The turn south to air carrier X turned air carrier X into air carrier Y. Investigation revealed 2.8 mi at same altitude.

Original NASA ASRS Text

Title: ACR X HAD LTSS FROM ACR Y. SYS ERROR.

Narrative: I WAS VECTORING ACR X 25 MI SW OF SEA FOR AN ILS APCH TO SEA. I WAS ALSO VECTORING ACR Y FROM THE SE TO FOLLOW ACR X. ACR Z CAME ON MY FREQ AND RPTED SEA IN SIGHT. I TURNED ACR Z TO THE E TO SEE TFC PLANNING A VISUAL APCH TO RWY 34L. AT THIS TIME I ASKED ACR X (BUT I WAS LOOKING AT AND THINKING ACR Z) IF HE SAW THE TFC FOR THE R RWY. ACR X SAID NO AND THAT THEY DID NOT HAVE THE RWY AT SEA EITHER. I THEN TURNED ACR X (STILL THINKING ACR Z) TO A R TURN HDG 160. THIS PLACED ACR X IN CONFLICT WITH ACR Y. I REALIZED MY ERROR AND ATTEMPTED TO SEPARATE ACR X AND ACR Y. ACR Y REFUSED TO TAKE ONE OF MY INSTRUCTIONS BECAUSE THEY WERE GETTING AN ONBOARD TCAS ALARM. I RECALL WAITING FOREVER FOR EACH RADAR SWEEP TO UPDATE BECAUSE ONE ACFT WAS IN COAST SO I COULD GIVE ADDITIONAL INSTRUCTIONS. THE ACFT SEPARATED AND LANDED NORMAL. A REVIEW BY BOTH PLTS AND MYSELF AS WE LISTEN TO THE TAPE MIGHT BE HELPFUL, SINCE ACR Y HAD INFO I DID NOT (TCAS). SIMILAR CALL SIGNS MIGHT HAVE CONTRIBUTED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFORMATION: THE RPTR STATED BOTH ACFT HAD GONE INTO COAST STATUS. ACR Y REFUSED A DSCNT CLRNC BECAUSE OF A TCASII TFC ALERT NOT A RESOLUTION ALERT. THE TURN S TO ACR X TURNED ACR X INTO ACR Y. INVESTIGATION REVEALED 2.8 MI AT SAME ALT.

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.