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

Attributes
ACN	139469
Time
Date	199003
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lvl
State Reference	VA
Altitude	msl bound lower : 16000 msl bound upper : 16000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 2 controller radar : 1
ASRS Report	139469
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : private
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : required legal separation non adherence : published procedure non adherence : clearance
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	none taken : detected after the fact
Consequence	faa : investigated
Miss Distance	horizontal : 15000 vertical : 200
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Aircraft X was southbound over lvl at 16000'. Air carrier Y northbound over lvl needing to land at richmond. Aircraft X was given a clearance to 15000' and later amended to 17000' when it became apparent that the aircraft was not descending fast enough to get below aircraft Y. Same company air carrier called ATC climbing to 10000' off of raleigh-durham. He was cleared to 18000'. Another aircraft was handed off at 17000' in conflict with air carrier similar a/north. I amended similar a/north to 16000' though subsequent playback of the tape recording sounds as if I stated air carrier X in clearance. During the readback of this clearance it was unclear which aircraft took the clearance. Later air carrier X descended to 16000' because he believed that was his assigned altitude. This put the aircraft dangerously close to aircraft X already at 16000'. There was not adequate recognition amongst the controllers or pilots that there were similar sounding call signs. Stronger emphasis on this might have prevented this occurrence. If there is a possibility of air carrier's avoiding similar call signs completely this would be preferable.

Original NASA ASRS Text

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

Narrative: ACFT X WAS SBND OVER LVL AT 16000'. ACR Y NBOUND OVER LVL NEEDING TO LAND AT RICHMOND. ACFT X WAS GIVEN A CLRNC TO 15000' AND LATER AMENDED TO 17000' WHEN IT BECAME APPARENT THAT THE ACFT WAS NOT DSNDING FAST ENOUGH TO GET BELOW ACFT Y. SAME COMPANY ACR CALLED ATC CLBING TO 10000' OFF OF RALEIGH-DURHAM. HE WAS CLRED TO 18000'. ANOTHER ACFT WAS HANDED OFF AT 17000' IN CONFLICT WITH ACR SIMILAR A/N. I AMENDED SIMILAR A/N TO 16000' THOUGH SUBSEQUENT PLAYBACK OF THE TAPE RECORDING SOUNDS AS IF I STATED ACR X IN CLRNC. DURING THE READBACK OF THIS CLRNC IT WAS UNCLEAR WHICH ACFT TOOK THE CLRNC. LATER ACR X DSNDED TO 16000' BECAUSE HE BELIEVED THAT WAS HIS ASSIGNED ALT. THIS PUT THE ACFT DANGEROUSLY CLOSE TO ACFT X ALREADY AT 16000'. THERE WAS NOT ADEQUATE RECOGNITION AMONGST THE CTLRS OR PLTS THAT THERE WERE SIMILAR SOUNDING CALL SIGNS. STRONGER EMPHASIS ON THIS MIGHT HAVE PREVENTED THIS OCCURRENCE. IF THERE IS A POSSIBILITY OF ACR'S AVOIDING SIMILAR CALL SIGNS COMPLETELY THIS WOULD BE PREFERABLE.

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.