B757 flight crew has a TCAS TA during a descent.

Attributes
ACN	699912
Time
Date	200606
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : zab.artcc
State Reference	NM
Altitude	msl single value : 34400
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zab.artcc
Operator	common carrier : air carrier
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zab.artcc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	699912
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	699911
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	aircraft equipment : tcas other flight crewa other flight crewb
Resolutory Action	controller : issued advisory controller : issued new clearance
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	ATC Human Performance

Narrative:

We were descending from FL360 to FL340; when the controller had issued a new descent to FL300 in 4 mins. We read back his instructions and were complying with the new clearance. At FL344 we had a TA; then the controller asked if we were at FL340. He said that we were to be at FL340; which I then disputed. The controller then asked if another flight was descending to FL300; and he said he was not. Apparently the controller had confused our flts with each other. Supplemental information from acn 699911: when passing through FL320 ATC said; 'verify you're level at FL340.' then we heard a new voice on ATC (possibly a supervisor) say to us; 'continue descent to FL300?' the other aircraft was called by ATC and he said over the frequency; 'I heard the entire transmission.' we called ZAB when on the ground. The supervisor confirmed with the captain that the controller had made a mistake and the incident was under investigation.

Original NASA ASRS Text

Title: B757 FLT CREW HAS A TCAS TA DURING A DSCNT.

Narrative: WE WERE DSNDING FROM FL360 TO FL340; WHEN THE CTLR HAD ISSUED A NEW DSCNT TO FL300 IN 4 MINS. WE READ BACK HIS INSTRUCTIONS AND WERE COMPLYING WITH THE NEW CLRNC. AT FL344 WE HAD A TA; THEN THE CTLR ASKED IF WE WERE AT FL340. HE SAID THAT WE WERE TO BE AT FL340; WHICH I THEN DISPUTED. THE CTLR THEN ASKED IF ANOTHER FLT WAS DSNDING TO FL300; AND HE SAID HE WAS NOT. APPARENTLY THE CTLR HAD CONFUSED OUR FLTS WITH EACH OTHER. SUPPLEMENTAL INFO FROM ACN 699911: WHEN PASSING THROUGH FL320 ATC SAID; 'VERIFY YOU'RE LEVEL AT FL340.' THEN WE HEARD A NEW VOICE ON ATC (POSSIBLY A SUPVR) SAY TO US; 'CONTINUE DSCNT TO FL300?' THE OTHER ACFT WAS CALLED BY ATC AND HE SAID OVER THE FREQ; 'I HEARD THE ENTIRE XMISSION.' WE CALLED ZAB WHEN ON THE GND. THE SUPVR CONFIRMED WITH THE CAPT THAT THE CTLR HAD MADE A MISTAKE AND THE INCIDENT WAS UNDER INVESTIGATION.

Data retrieved from NASA's ASRS site as of January 2009 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.