Air carrier takes another aircraft's clearance and descends resulting in a TCASII RA.

Attributes
ACN	455948
Time
Date	199911
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : cvg.vortac
State Reference	OH
Altitude	msl bound lower : 23000 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Dawn
Aircraft 1
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Route In Use	arrival star : cince 3
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : atp
Experience	flight time last 90 days : 110 flight time total : 12000 flight time type : 800
ASRS Report	455948
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : multi engine
Experience	flight time last 90 days : 240 flight time total : 2980 flight time type : 800
ASRS Report	455946
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : published procedure non adherence : company policies
Independent Detector	aircraft equipment : tcas other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : took precautionary avoidance action flight crew : took evasive action
Miss Distance	horizontal : 18000 vertical : 1000
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

At FL240, ZID issued a descent clearance. Thinking it was ours, my first officer read it back and I started the descent. Shortly thereafter we received a TA then an RA, when ATC cleared us back up to FL240. The traffic was a DC8 climbing. We had the traffic in sight when we received the TA and could see that it would pass safely to our left. Thinking controller error, we thought nothing more of it until we were parked at the gate and were given a phone number to call. We found out later that we had answered another flight's descent clearance.

Original NASA ASRS Text

Title: ACR TAKES ANOTHER ACFT'S CLRNC AND DSNDS RESULTING IN A TCASII RA.

Narrative: AT FL240, ZID ISSUED A DSCNT CLRNC. THINKING IT WAS OURS, MY FO READ IT BACK AND I STARTED THE DSCNT. SHORTLY THEREAFTER WE RECEIVED A TA THEN AN RA, WHEN ATC CLRED US BACK UP TO FL240. THE TFC WAS A DC8 CLBING. WE HAD THE TFC IN SIGHT WHEN WE RECEIVED THE TA AND COULD SEE THAT IT WOULD PASS SAFELY TO OUR L. THINKING CTLR ERROR, WE THOUGHT NOTHING MORE OF IT UNTIL WE WERE PARKED AT THE GATE AND WERE GIVEN A PHONE NUMBER TO CALL. WE FOUND OUT LATER THAT WE HAD ANSWERED ANOTHER FLT'S DSCNT CLRNC.

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.