An A320 pilot reports false TCAS targets at cruise altitude leading to RA evasive climb. No traffic in aircraft's vicinity rprted by ATC. Possible TCAS supression bus failure.

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Attributes
ACN	768742
Time
Date	200801
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 36000
Environment
Flight Conditions	VMC
Aircraft 1
Controlling Facilities	artcc : zzz.artcc tower : clt.tower
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 150 flight time total : 15000 flight time type : 3500
ASRS Report	768742
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude
Independent Detector	aircraft equipment : tcas other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : took evasive action
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Received RA 'climb climb' after one 'traffic' at cruise. Responded as trained with immediate climb. ATC said no target; descended back to FL360 and turned TCAS off per maintenance instruction for duration of flight. Phantom target remained on top of our position for about 10 minutes and disappeared. No loss of separation. False TCAS RA.callback conversation with reporter revealed the following information: reporter stated that when the TCAS RA occurred his hand was closest to the controls and therefore he immediately responded to the climb command. Because he had had a real TCAS the previous month he felt primed for this event. The first officer immediately called ATC who replied that there was no traffic in their vicinity. The crew descended to FL360 and contacted maintenance and were advised to turn the TCAS to TA only. Previously the flight crew was watching traffic ahead so when the target appeared they were immediately suspicious but had to respond. The reporter stated that this aircraft did not have a history of TCAS faults up to that flight.

Original NASA ASRS Text

Title: AN A320 PLT RPTS FALSE TCAS TARGETS AT CRUISE ALT LEADING TO RA EVASIVE CLB. NO TFC IN ACFT'S VICINITY RPRTED BY ATC. POSSIBLE TCAS SUPRESSION BUS FAILURE.

Narrative: RECEIVED RA 'CLB CLB' AFTER ONE 'TRAFFIC' AT CRUISE. RESPONDED AS TRAINED WITH IMMEDIATE CLB. ATC SAID NO TARGET; DSNDED BACK TO FL360 AND TURNED TCAS OFF PER MAINT INSTRUCTION FOR DURATION OF FLT. PHANTOM TARGET REMAINED ON TOP OF OUR POSITION FOR ABOUT 10 MINUTES AND DISAPPEARED. NO LOSS OF SEPARATION. FALSE TCAS RA.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT WHEN THE TCAS RA OCCURRED HIS HAND WAS CLOSEST TO THE CTLS AND THEREFORE HE IMMEDIATELY RESPONDED TO THE CLB COMMAND. BECAUSE HE HAD HAD A REAL TCAS THE PREVIOUS MONTH HE FELT PRIMED FOR THIS EVENT. THE FO IMMEDIATELY CALLED ATC WHO REPLIED THAT THERE WAS NO TFC IN THEIR VICINITY. THE CREW DSNDED TO FL360 AND CONTACTED MAINT AND WERE ADVISED TO TURN THE TCAS TO TA ONLY. PREVIOUSLY THE FLT CREW WAS WATCHING TFC AHEAD SO WHEN THE TARGET APPEARED THEY WERE IMMEDIATELY SUSPICIOUS BUT HAD TO RESPOND. THE RPTR STATED THAT THIS ACFT DID NOT HAVE A HISTORY OF TCAS FAULTS UP TO THAT FLT.

Data retrieved from NASA's ASRS site as of May 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.