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

Attributes
ACN	121572
Time
Date	198909
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : eau
State Reference	WI
Altitude	msl bound lower : 27000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zmp
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Heavy Transport, Low Wing, 4 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 4 controller radar : 1
ASRS Report	121572
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	none taken : unable none taken : detected after the fact
Consequence	faa : investigated
Miss Distance	horizontal : 21000 vertical : 700
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X checked on frequency. He was eastbound on J106. I cleared him to FL330. Later I got the handoff on air carrier Y, heavy wbound on J106 at FL310. I reclred air carrier X to FL290. A little while later, air carrier X called asking if I had called him. I said no, thinking I had already gotten the acknowledgement on the altitude change. When the 2 got closer together, I called traffic for both. When they were side by side, I put air carrier X on sector 14's frequency, and saw him leave FL290 right at the end of my transmission. After listening to the tape, it was obvious I did not get the acknowledgement from air carrier X, because aircraft called asking which chicago frequency he was supposed to be on. Callback conversation with reporter revealed the following: air carrier X type aircraft: 3 engine large transport. Reporter's experience: 1 yr radar, 4 yrs non radar. Flight conditions: VMC. Time of occurrence: 2. Place: eau 20 mi east. EST miss: 700' vertical, 21000' horizontal. Reporter stated the facility processed this as a system error. Computer detected error.

Original NASA ASRS Text

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

Narrative: ACR X CHKED ON FREQ. HE WAS EBND ON J106. I CLRED HIM TO FL330. LATER I GOT THE HDOF ON ACR Y, HVY WBOUND ON J106 AT FL310. I RECLRED ACR X TO FL290. A LITTLE WHILE LATER, ACR X CALLED ASKING IF I HAD CALLED HIM. I SAID NO, THINKING I HAD ALREADY GOTTEN THE ACKNOWLEDGEMENT ON THE ALT CHANGE. WHEN THE 2 GOT CLOSER TOGETHER, I CALLED TFC FOR BOTH. WHEN THEY WERE SIDE BY SIDE, I PUT ACR X ON SECTOR 14'S FREQ, AND SAW HIM LEAVE FL290 RIGHT AT THE END OF MY XMISSION. AFTER LISTENING TO THE TAPE, IT WAS OBVIOUS I DID NOT GET THE ACKNOWLEDGEMENT FROM ACR X, BECAUSE ACFT CALLED ASKING WHICH CHICAGO FREQ HE WAS SUPPOSED TO BE ON. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: ACR X TYPE ACFT: 3 ENG LGT. RPTR'S EXPERIENCE: 1 YR RADAR, 4 YRS NON RADAR. FLT CONDITIONS: VMC. TIME OF OCCURRENCE: 2. PLACE: EAU 20 MI E. EST MISS: 700' VERT, 21000' HORIZ. RPTR STATED THE FAC PROCESSED THIS AS A SYS ERROR. COMPUTER DETECTED ERROR.

Data retrieved from NASA's ASRS site as of August 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.