Medium large transport aircraft in cruise received TCASII RA, followed it and then the flight crew realized that the target stayed in the same relative position. Investigation revealed that the TCASII had been written up 3 times recently.

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Attributes
ACN	363071
Time
Date	199703
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : vbg
State Reference	CA
Altitude	msl bound lower : 33500 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	enroute airway : j501
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : commercial pilot : flight engineer pilot : cfi pilot : atp
Experience	flight time last 90 days : 150 flight time total : 10000 flight time type : 2000
ASRS Report	363071
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : excursion from assigned altitude other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

We were level FL350, received TCASII TA 12 O'clock position and 1 mi, then descend RA, zero altitude difference. Responded -- had to descend to FL335. Target stayed merged with us. Switched xponders at FL335 and target disappeared. Suspect false RA. Further investigation revealed that TCASII had been written up 3 times recently for same problem.

Original NASA ASRS Text

Title: MLG ACFT IN CRUISE RECEIVED TCASII RA, FOLLOWED IT AND THEN THE FLC REALIZED THAT THE TARGET STAYED IN THE SAME RELATIVE POS. INVESTIGATION REVEALED THAT THE TCASII HAD BEEN WRITTEN UP 3 TIMES RECENTLY.

Narrative: WE WERE LEVEL FL350, RECEIVED TCASII TA 12 O'CLOCK POS AND 1 MI, THEN DSND RA, ZERO ALT DIFFERENCE. RESPONDED -- HAD TO DSND TO FL335. TARGET STAYED MERGED WITH US. SWITCHED XPONDERS AT FL335 AND TARGET DISAPPEARED. SUSPECT FALSE RA. FURTHER INVESTIGATION REVEALED THAT TCASII HAD BEEN WRITTEN UP 3 TIMES RECENTLY FOR SAME PROB.

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.