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

Attributes
ACN	138806
Time
Date	199003
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : bwi
State Reference	MD
Altitude	msl bound lower : 4000 msl bound upper : 5000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bwi
Operator	common carrier : air carrier
Make Model Name	Medium Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other descent other
Route In Use	arrival other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	climbout : intermediate altitude
Route In Use	departure other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 1
ASRS Report	138806
Person 2
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 3000 vertical : 300
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Intra Facility Coordination Failure Operational Error

Narrative:

I controled an arriving air carrier X mdt on a base leg for runway 33L. I expected the air carrier X to be handed off to me at 4000' by SOP and failed to ensure the aircraft would be level or below 400' at the proper airspace boundary. Eventually air carrier X conflicted with an air carrier Y departure, but not before I noticed the potential conflict with legal sep. After all control instructions were issued, final sep decreased to approximately 1/2 mi/300'. The position (south final) was combined and working (north final) traffic due to maintenance problems. Traffic was moderate-heavy during this inbound rush. Air carrier X was handed off by a training controller and another controller also observed air carrier X at 5000', but failed to bring it to my attention. These factors along with my own failure to recognize the situation is timely fashion are responsible for the error.

Original NASA ASRS Text

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

Narrative: I CTLED AN ARRIVING ACR X MDT ON A BASE LEG FOR RWY 33L. I EXPECTED THE ACR X TO BE HANDED OFF TO ME AT 4000' BY SOP AND FAILED TO ENSURE THE ACFT WOULD BE LEVEL OR BELOW 400' AT THE PROPER AIRSPACE BOUNDARY. EVENTUALLY ACR X CONFLICTED WITH AN ACR Y DEP, BUT NOT BEFORE I NOTICED THE POTENTIAL CONFLICT WITH LEGAL SEP. AFTER ALL CTL INSTRUCTIONS WERE ISSUED, FINAL SEP DECREASED TO APPROX 1/2 MI/300'. THE POS (S FINAL) WAS COMBINED AND WORKING (N FINAL) TFC DUE TO MAINT PROBS. TFC WAS MODERATE-HVY DURING THIS INBND RUSH. ACR X WAS HANDED OFF BY A TRNING CTLR AND ANOTHER CTLR ALSO OBSERVED ACR X AT 5000', BUT FAILED TO BRING IT TO MY ATTN. THESE FACTORS ALONG WITH MY OWN FAILURE TO RECOGNIZE THE SITUATION IS TIMELY FASHION ARE RESPONSIBLE FOR THE ERROR.

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.