DC8-71 crew had TCASII RA's from a malfunctioning TCASII system.

Attributes
ACN	574960
Time
Date	200302
Day	Sun
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : sjc.airport
State Reference	CA
Altitude	msl single value : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa.artcc
Operator	common carrier : air carrier
Make Model Name	DC-8 70
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Route In Use	departure : on vectors enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 10300 flight time type : 4000
ASRS Report	574960
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	aircraft equipment : tcas other flight crewa other flight crewb
Resolutory Action	controller : issued advisory flight crew : returned to assigned altitude flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Level flight, TCASII sounds RA to descend at 2500 FPM to avoid traffic displayed at '00' distance from our aircraft. No traffic previously reported by ATC. Advised ATC while responding to descent command. In process, ATC advised no traffic and of terrain in area. About 4000 ft MSL, TCASII RA and commanded climb at better than 2000 FPM. Advised ATC and at same time responded, still with '00' target displayed on TCASII screen. Again, ATC said nothing about a traffic target anywhere near us. Proceeded on vector to concord VOR, then destination. TCASII checked ok on preflight and postflt, logbook entry for possible false command on arrival at destination. Captain talked to ATC on phone and advised them of what happened, ATC said no traffic conflict occurred on their side, and we attributed it to a false command by onboard equipment malfunction. The recent aircraft TCASII incident was mentioned in our debrief amongst our crew that led us to fly the command and talk as we reacted.

Original NASA ASRS Text

Title: DC8-71 CREW HAD TCASII RA'S FROM A MALFUNCTIONING TCASII SYS.

Narrative: LEVEL FLT, TCASII SOUNDS RA TO DSND AT 2500 FPM TO AVOID TFC DISPLAYED AT '00' DISTANCE FROM OUR ACFT. NO TFC PREVIOUSLY RPTED BY ATC. ADVISED ATC WHILE RESPONDING TO DSCNT COMMAND. IN PROCESS, ATC ADVISED NO TFC AND OF TERRAIN IN AREA. ABOUT 4000 FT MSL, TCASII RA AND COMMANDED CLB AT BETTER THAN 2000 FPM. ADVISED ATC AND AT SAME TIME RESPONDED, STILL WITH '00' TARGET DISPLAYED ON TCASII SCREEN. AGAIN, ATC SAID NOTHING ABOUT A TFC TARGET ANYWHERE NEAR US. PROCEEDED ON VECTOR TO CONCORD VOR, THEN DEST. TCASII CHKED OK ON PREFLT AND POSTFLT, LOGBOOK ENTRY FOR POSSIBLE FALSE COMMAND ON ARR AT DEST. CAPT TALKED TO ATC ON PHONE AND ADVISED THEM OF WHAT HAPPENED, ATC SAID NO TFC CONFLICT OCCURRED ON THEIR SIDE, AND WE ATTRIBUTED IT TO A FALSE COMMAND BY ONBOARD EQUIP MALFUNCTION. THE RECENT ACFT TCASII INCIDENT WAS MENTIONED IN OUR DEBRIEF AMONGST OUR CREW THAT LED US TO FLY THE COMMAND AND TALK AS WE REACTED.

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.