MTR had less than standard separation from aircraft Y. System error.

Attributes
ACN	198810
Time
Date	199201
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mei
State Reference	MS
Altitude	msl bound lower : 7000 msl bound upper : 8000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mei
Operator	other
Make Model Name	Military Trainer
Flight Phase	cruise other descent other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach instruction : instructor
Qualification	controller : radar
ASRS Report	198810
Person 2
Affiliation	government : faa
Function	controller : approach instruction : trainee
Qualification	controller : developmental
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	faa : investigated
Miss Distance	horizontal : 12000 vertical : 700
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was training a developmental on the west sector. We accepted an automated handoff from memphis center on an MTR sbound at 8000 ft. The developmental issued a descent clearance to 5000 ft and advance approach information. He then issued a clearance to MTR to maintain 8000 ft. I observed the altitude readout indicating 7700. I intervened and issued MTR a climb to 8000 ft and called traffic. The altitude readout then indicated 'XXX' (meaning unknown). At no time did I feel I lost 3 mi lateral separation prior to reestablishing 1000 ft vertical separation. MTR reported aircraft Y in sight. I instructed him to maintain visual separation from the traffic. The next mode C (altitude) readout indicated 8000. I was informed that the pilot complained and less than min separation existed. I was decertified on the radar control position pending training and recertification.

Original NASA ASRS Text

Title: MTR HAD LTSS FROM ACFT Y. SYS ERROR.

Narrative: I WAS TRAINING A DEVELOPMENTAL ON THE W SECTOR. WE ACCEPTED AN AUTOMATED HDOF FROM MEMPHIS CENTER ON AN MTR SBOUND AT 8000 FT. THE DEVELOPMENTAL ISSUED A DSCNT CLRNC TO 5000 FT AND ADVANCE APCH INFO. HE THEN ISSUED A CLRNC TO MTR TO MAINTAIN 8000 FT. I OBSERVED THE ALT READOUT INDICATING 7700. I INTERVENED AND ISSUED MTR A CLB TO 8000 FT AND CALLED TFC. THE ALT READOUT THEN INDICATED 'XXX' (MEANING UNKNOWN). AT NO TIME DID I FEEL I LOST 3 MI LATERAL SEPARATION PRIOR TO REESTABLISHING 1000 FT VERT SEPARATION. MTR RPTED ACFT Y IN SIGHT. I INSTRUCTED HIM TO MAINTAIN VISUAL SEPARATION FROM THE TFC. THE NEXT MODE C (ALT) READOUT INDICATED 8000. I WAS INFORMED THAT THE PLT COMPLAINED AND LESS THAN MIN SEPARATION EXISTED. I WAS DECERTIFIED ON THE RADAR CTL POS PENDING TRAINING AND RECERTIFICATION.

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.