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

Attributes
ACN	123708
Time
Date	198909
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : zbw
State Reference	MA
Altitude	msl bound lower : 20400 msl bound upper : 21000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zbw
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Widebody Transport
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
ASRS Report	123708
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
Resolutory Action	controller : issued new clearance
Consequence	faa : investigated
Miss Distance	vertical : 600
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was working 2 aircraft that were involved in a possible operational error/pilot deviation. The call signs were air carrier X and air carrier Y. Air carrier Y checked on leaving FL200 climbing to FL230. The aircraft was instructed to maintain FL200. His response: 'leveling at 200.' I then asked air carrier X to verify leaving FL210. His reply was, 'roger, leaving 210 for 260.' I had therefore established 1000' vertical sep. 2 radar hits later air carrier Y's altitude read FL204. I asked the aircraft to verify level at FL200. His response was, 'yeah, we're level. We overshot a bit; we're gettin' back to it.' I was then removed from the radar position and the investigation began into the operational error/pilot deviation.

Original NASA ASRS Text

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

Narrative: I WAS WORKING 2 ACFT THAT WERE INVOLVED IN A POSSIBLE OPERROR/PLTDEV. THE CALL SIGNS WERE ACR X AND ACR Y. ACR Y CHKED ON LEAVING FL200 CLBING TO FL230. THE ACFT WAS INSTRUCTED TO MAINTAIN FL200. HIS RESPONSE: 'LEVELING AT 200.' I THEN ASKED ACR X TO VERIFY LEAVING FL210. HIS REPLY WAS, 'ROGER, LEAVING 210 FOR 260.' I HAD THEREFORE ESTABLISHED 1000' VERT SEP. 2 RADAR HITS LATER ACR Y'S ALT READ FL204. I ASKED THE ACFT TO VERIFY LEVEL AT FL200. HIS RESPONSE WAS, 'YEAH, WE'RE LEVEL. WE OVERSHOT A BIT; WE'RE GETTIN' BACK TO IT.' I WAS THEN REMOVED FROM THE RADAR POS AND THE INVESTIGATION BEGAN INTO THE OPERROR/PLT DEV.

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.