An ARTCC radar controller mistakenly gave a descent clearance to an occupied altitude.

Attributes
ACN	303264
Time
Date	199504
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : lit
State Reference	AR
Altitude	msl bound lower : 28600 msl bound upper : 29000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Route In Use	enroute airway : j101
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	other : unknown
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : cfi
ASRS Report	303264
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 17000 flight time type : 4000
ASRS Report	303709
Events
Anomaly	conflict : airborne less severe non adherence : far non adherence : required legal separation other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	controller : issued new clearance flight crew : returned to intended course or assigned course flight crew : took evasive action
Consequence	Other
Miss Distance	vertical : 600
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

ZME cleared air carrier X to descend from FL290 to FL270. We replied, 'air carrier X descend to FL270.' again, ZME cleared us to descend to FL270 and we replied, 'descend to FL270.' at FL286 ZME cleared us to maintain FL290. We replied with 'air carrier X, maintain FL290.' at this time we received a TCASII TA alert at 3 O'clock and 600 ft below us. We immediately transitioned from a descent to a maximum performance climb, back to FL290. In the process, ATC made several xmissions concerned with our altitude. We replied, maintain FL290. Upon reaching FL290 the TA alert was resolved without receiving and RA from the TCASII. The problem was solved and ZME apologized. The horizontal distance of the traffic was hard to determine, because we had the WX radar turned on.

Original NASA ASRS Text

Title: AN ARTCC RADAR CTLR MISTAKENLY GAVE A DSCNT CLRNC TO AN OCCUPIED ALT.

Narrative: ZME CLRED ACR X TO DSND FROM FL290 TO FL270. WE REPLIED, 'ACR X DSND TO FL270.' AGAIN, ZME CLRED US TO DSND TO FL270 AND WE REPLIED, 'DSND TO FL270.' AT FL286 ZME CLRED US TO MAINTAIN FL290. WE REPLIED WITH 'ACR X, MAINTAIN FL290.' AT THIS TIME WE RECEIVED A TCASII TA ALERT AT 3 O'CLOCK AND 600 FT BELOW US. WE IMMEDIATELY TRANSITIONED FROM A DSCNT TO A MAX PERFORMANCE CLB, BACK TO FL290. IN THE PROCESS, ATC MADE SEVERAL XMISSIONS CONCERNED WITH OUR ALT. WE REPLIED, MAINTAIN FL290. UPON REACHING FL290 THE TA ALERT WAS RESOLVED WITHOUT RECEIVING AND RA FROM THE TCASII. THE PROB WAS SOLVED AND ZME APOLOGIZED. THE HORIZ DISTANCE OF THE TFC WAS HARD TO DETERMINE, BECAUSE WE HAD THE WX RADAR TURNED ON.

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.