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

Attributes
ACN	132249
Time
Date	198912
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : msp
State Reference	MN
Altitude	msl bound lower : 6000 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : msp artcc : zdc
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
Experience	controller military : 4 controller radar : 10
ASRS Report	132249
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
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 1200 vertical : 900
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Working departure radar. Only had 2 airplanes. The first one, am medium large transport, turned to a southwest heading. The second, an medium large transport. The air carrier X was 1500 above the air carrier Y and out-climbing air carrier Y. I turned the air carrier Y to a ssw heading and turned for a minute to join a conversation. When I turned back to the scope, the air carrier Y was turning inside air carrier X and catching him in altitude. I leveled off the air carrier Y and issued traffic. What happened? I thought the air carrier X, medium large transport, would way out-perform the air carrier Y, medium large transport. It didn't happen that way. Lesson: pay more attention when slow. Don't assume anything.

Original NASA ASRS Text

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

Narrative: WORKING DEP RADAR. ONLY HAD 2 AIRPLANES. THE FIRST ONE, AM MLG, TURNED TO A SW HDG. THE SECOND, AN MLG. THE ACR X WAS 1500 ABOVE THE ACR Y AND OUT-CLIMBING ACR Y. I TURNED THE ACR Y TO A SSW HDG AND TURNED FOR A MINUTE TO JOIN A CONVERSATION. WHEN I TURNED BACK TO THE SCOPE, THE ACR Y WAS TURNING INSIDE ACR X AND CATCHING HIM IN ALT. I LEVELED OFF THE ACR Y AND ISSUED TFC. WHAT HAPPENED? I THOUGHT THE ACR X, MLG, WOULD WAY OUT-PERFORM THE ACR Y, MLG. IT DIDN'T HAPPEN THAT WAY. LESSON: PAY MORE ATTN WHEN SLOW. DON'T ASSUME ANYTHING.

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.