ZOB ARTCC controller clears traffic at 16000 ft to 14000 ft with conflicting traffic at 15000 ft.

Attributes
ACN	450736
Time
Date	199910
Day	Fri
Local Time Of Day	0001 To 0600
Place
Locale Reference	atc facility : zob.artcc
State Reference	OH
Altitude	msl bound lower : 15800 msl bound upper : 16000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob.artcc
Operator	common carrier : air carrier
Make Model Name	Beech 1900
Operating Under FAR Part	Part 135
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zob.artcc
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 15
ASRS Report	450736
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	atc equipment : conflict alert aircraft equipment : tcas other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : returned to assigned altitude
Miss Distance	horizontal : 12000 vertical : 700
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier Y was level 15000 ft. Air carrier X was at 16000 ft. I descended air carrier X to 14000 ft, caught the error and told him to maintain 16000 ft. He replied, 'we'll stay at 16000 ft.' then he descended down and back up. I had him verify altitude and he said he was level 16000 ft, but had gone down 200 ft and back up. I had 15 aircraft on frequency, and there was lots of data block overlap. D-side was in the process of briefing and traffic was complex.

Original NASA ASRS Text

Title: ZOB ARTCC CTLR CLRS TFC AT 16000 FT TO 14000 FT WITH CONFLICTING TFC AT 15000 FT.

Narrative: ACR Y WAS LEVEL 15000 FT. ACR X WAS AT 16000 FT. I DSNDED ACR X TO 14000 FT, CAUGHT THE ERROR AND TOLD HIM TO MAINTAIN 16000 FT. HE REPLIED, 'WE'LL STAY AT 16000 FT.' THEN HE DSNDED DOWN AND BACK UP. I HAD HIM VERIFY ALT AND HE SAID HE WAS LEVEL 16000 FT, BUT HAD GONE DOWN 200 FT AND BACK UP. I HAD 15 ACFT ON FREQ, AND THERE WAS LOTS OF DATA BLOCK OVERLAP. D-SIDE WAS IN THE PROCESS OF BRIEFING AND TFC WAS COMPLEX.

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.