Less than standard separation between air carrier X and small transport Y. System error.

Attributes
ACN	126598
Time
Date	198909
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : oma
State Reference	NE
Altitude	msl bound lower : 4000 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : oma
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Transport
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 7
ASRS Report	126598
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 flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew faa : investigated
Miss Distance	horizontal : 2000 vertical : 200
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X was assigned an altitude of 4000' with an small transport Y in its flight path also at 4000'. I thought I had assigned the air carrier X 5000', but my strip indicated 4000' and the pilot also confirmed I had said 4000'. This problem could have been avoided by me listening to the readback, scanning both the scope and strips better.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN ACR X AND SMT Y. SYSTEM ERROR.

Narrative: ACR X WAS ASSIGNED AN ALT OF 4000' WITH AN SMT Y IN ITS FLT PATH ALSO AT 4000'. I THOUGHT I HAD ASSIGNED THE ACR X 5000', BUT MY STRIP INDICATED 4000' AND THE PLT ALSO CONFIRMED I HAD SAID 4000'. THIS PROB COULD HAVE BEEN AVOIDED BY ME LISTENING TO THE READBACK, SCANNING BOTH THE SCOPE AND STRIPS BETTER.

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.