ARTCC radar controller issued wrong altitude to an air carrier A320 and then handed the aircraft off to the next sector. The data block showed FL330, but the aircraft reported in descending to FL310. The receiving controller caught the error and corrected the altitude assignment, but not before less than standard separation occurred.

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Attributes
ACN	361380
Time
Date	199702
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : air
State Reference	OH
Altitude	msl bound lower : 31000 msl bound upper : 32200
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zob
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 3 controller radar : 4
ASRS Report	361380
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 3 controller radar : 5
ASRS Report	361384
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 19500 vertical : 1200
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Aircraft #1 was coordinated at FL330 for traffic below at FL310. When aircraft #1 checked in, he was stepped on by another aircraft reading back a clearance. I couldn't understand either aircraft so I answered the aircraft I had given the clearance to. When aircraft #1 checked in again, he reported leaving FL327 for FL310. I immediately climbed aircraft #1 back to FL330 but separation was lost. The tapes indicated that the previous controller had erroneously cleared aircraft #1 to FL310, not FL330 as coordinated. Supplemental information from acn 361384: aircraft #2 was in level flight at FL310 2 mi behind aircraft #1. Aircraft #1 was issued pilot's discretion to FL330. Later aircraft #1 was asked to descend to FL310 and read back FL310. Controller had FL330 in data block, but issued FL310 by mistake and missed readback. Controller wanted aircraft #1 to descend only to FL330 -- had FL330 in data block and thought he said FL330.

Original NASA ASRS Text

Title: ARTCC RADAR CTLR ISSUED WRONG ALT TO AN ACR A320 AND THEN HANDED THE ACFT OFF TO THE NEXT SECTOR. THE DATA BLOCK SHOWED FL330, BUT THE ACFT RPTED IN DSNDING TO FL310. THE RECEIVING CTLR CAUGHT THE ERROR AND CORRECTED THE ALT ASSIGNMENT, BUT NOT BEFORE LTSS OCCURRED.

Narrative: ACFT #1 WAS COORDINATED AT FL330 FOR TFC BELOW AT FL310. WHEN ACFT #1 CHKED IN, HE WAS STEPPED ON BY ANOTHER ACFT READING BACK A CLRNC. I COULDN'T UNDERSTAND EITHER ACFT SO I ANSWERED THE ACFT I HAD GIVEN THE CLRNC TO. WHEN ACFT #1 CHKED IN AGAIN, HE RPTED LEAVING FL327 FOR FL310. I IMMEDIATELY CLBED ACFT #1 BACK TO FL330 BUT SEPARATION WAS LOST. THE TAPES INDICATED THAT THE PREVIOUS CTLR HAD ERRONEOUSLY CLRED ACFT #1 TO FL310, NOT FL330 AS COORDINATED. SUPPLEMENTAL INFO FROM ACN 361384: ACFT #2 WAS IN LEVEL FLT AT FL310 2 MI BEHIND ACFT #1. ACFT #1 WAS ISSUED PLT'S DISCRETION TO FL330. LATER ACFT #1 WAS ASKED TO DSND TO FL310 AND READ BACK FL310. CTLR HAD FL330 IN DATA BLOCK, BUT ISSUED FL310 BY MISTAKE AND MISSED READBACK. CTLR WANTED ACFT #1 TO DSND ONLY TO FL330 -- HAD FL330 IN DATA BLOCK AND THOUGHT HE SAID FL330.

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.