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

Attributes
ACN	195707
Time
Date	199112
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : mke
State Reference	WI
Altitude	msl bound lower : 4000 msl bound upper : 4000
Environment
Flight Conditions	Mixed
Light	Night
Aircraft 1
Controlling Facilities	tracon : mke
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller non radar : 2 controller radar : 7
ASRS Report	195707
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Miss Distance	horizontal : 12000 vertical : 500
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error Intra Facility Coordination Failure

Narrative:

It was a 3 aircraft control problem. My air carrier Z was on the localizer in the clouds. The other controller had 2 mlgs, one on left base and the other on left downwind. It was my job to determine the sequence. I said I'd follow air carrier Y on base. The other controller determined he could get the downwind air carrier X on the ground #1 and not jeopardize the given sequence. Both the medium large transport's were VMC. Air carrier X on ldw was cleared for a visual approach and turned base 5 northeast of the field, farther than anticipated by the controller. This forced air carrier Y on base leg to go through the final to maintain spacing. When I was told this by the controller, I did not take immediate action. Should I turn left, to where the traffic was, or right, where he would soon be? In retrospect, I believe I preferred the loss of separation in this controled situation to ordering the captain to make an abrupt maneuver which would highlight our poor technique. The situation was finally resolved with one s-turn vector for air carrier Z.

Original NASA ASRS Text

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

Narrative: IT WAS A 3 ACFT CTL PROBLEM. MY ACR Z WAS ON THE LOC IN THE CLOUDS. THE OTHER CTLR HAD 2 MLGS, ONE ON L BASE AND THE OTHER ON L DOWNWIND. IT WAS MY JOB TO DETERMINE THE SEQUENCE. I SAID I'D FOLLOW ACR Y ON BASE. THE OTHER CTLR DETERMINED HE COULD GET THE DOWNWIND ACR X ON THE GND #1 AND NOT JEOPARDIZE THE GIVEN SEQUENCE. BOTH THE MLG'S WERE VMC. ACR X ON LDW WAS CLRED FOR A VISUAL APCH AND TURNED BASE 5 NE OF THE FIELD, FARTHER THAN ANTICIPATED BY THE CTLR. THIS FORCED ACR Y ON BASE LEG TO GO THROUGH THE FINAL TO MAINTAIN SPACING. WHEN I WAS TOLD THIS BY THE CTLR, I DID NOT TAKE IMMEDIATE ACTION. SHOULD I TURN L, TO WHERE THE TFC WAS, OR R, WHERE HE WOULD SOON BE? IN RETROSPECT, I BELIEVE I PREFERRED THE LOSS OF SEPARATION IN THIS CTLED SITUATION TO ORDERING THE CAPT TO MAKE AN ABRUPT MANEUVER WHICH WOULD HIGHLIGHT OUR POOR TECHNIQUE. THE SITUATION WAS FINALLY RESOLVED WITH ONE S-TURN VECTOR FOR ACR Z.

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.