TCASII false warning.

Attributes
ACN	232165
Time
Date	199301
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : dag
State Reference	CA
Altitude	msl bound lower : 37000 msl bound upper : 37000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla artcc : zoa
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi pilot : commercial pilot : flight engineer pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 9000 flight time type : 2000
ASRS Report	232165
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : nmac other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action flight crew : returned to intended course or assigned course
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 0 vertical : 200
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

While in level cruise FL370 (cleared direct dag) we were asked by ZLA to turn 15 degrees left for traffic. Another aircraft was asked to turn 20 degrees right for traffic. Since there was some urgency in the controller's voice, we were keeping a close eye on the TCASII. I expanded my range to about the 40 mi scale. We observed 1 aircraft at 8 O'clock, about 20 mi, FL370, approximately same direction. Another aircraft was 1 O'clock, 15-20 mi, FL350, approximately opposite direction, passing on our right. (Neither of these aircraft appeared to be any factor.) suddenly, a target popped up at 9 O'clock, 2 or 3 mi, at FL370. It immediately turned yellow, with a TCASII 'traffic, traffic' TA. We were unable to spot the aircraft visually, and just a few seconds later the target turned red and we got a 'climb, climb' TCASII RA. We initiated a climb, and watched the target cross directly under us, and then out the right side, until at about our 4 O'clock position 1-2 mi, the target abruptly disappeared. We never got a clear of conflict message, nor did we ever see the aircraft visually. I was looking primarily outside (PNF). The captain stated that the maximum altitude he observed during our TCASII directed RA maneuver was 37200 ft. Center said they had no aircraft in the area that corresponded to our intruder. To the best of our knowledge, the target did not climb with us, but we are not sure on that. We had some problems early on with false targets appearing on TCASII. Most of these were due to the TCASII tracking your own transponder. These would usually pop up exactly at your position, and follow your track as well as your climbs and dscnts. I believe the software has been fixed to cure that problem. One other source of false targets I've heard of are 'parrots,' or ATC ground based xponders used to calibrate radar scopes. I would expect one of those to remain in a stationary ground location, and not pass under us from left to right.

Original NASA ASRS Text

Title: TCASII FALSE WARNING.

Narrative: WHILE IN LEVEL CRUISE FL370 (CLRED DIRECT DAG) WE WERE ASKED BY ZLA TO TURN 15 DEGS L FOR TFC. ANOTHER ACFT WAS ASKED TO TURN 20 DEGS R FOR TFC. SINCE THERE WAS SOME URGENCY IN THE CTLR'S VOICE, WE WERE KEEPING A CLOSE EYE ON THE TCASII. I EXPANDED MY RANGE TO ABOUT THE 40 MI SCALE. WE OBSERVED 1 ACFT AT 8 O'CLOCK, ABOUT 20 MI, FL370, APPROX SAME DIRECTION. ANOTHER ACFT WAS 1 O'CLOCK, 15-20 MI, FL350, APPROX OPPOSITE DIRECTION, PASSING ON OUR R. (NEITHER OF THESE ACFT APPEARED TO BE ANY FACTOR.) SUDDENLY, A TARGET POPPED UP AT 9 O'CLOCK, 2 OR 3 MI, AT FL370. IT IMMEDIATELY TURNED YELLOW, WITH A TCASII 'TFC, TFC' TA. WE WERE UNABLE TO SPOT THE ACFT VISUALLY, AND JUST A FEW SECONDS LATER THE TARGET TURNED RED AND WE GOT A 'CLB, CLB' TCASII RA. WE INITIATED A CLB, AND WATCHED THE TARGET CROSS DIRECTLY UNDER US, AND THEN OUT THE R SIDE, UNTIL AT ABOUT OUR 4 O'CLOCK POS 1-2 MI, THE TARGET ABRUPTLY DISAPPEARED. WE NEVER GOT A CLR OF CONFLICT MESSAGE, NOR DID WE EVER SEE THE ACFT VISUALLY. I WAS LOOKING PRIMARILY OUTSIDE (PNF). THE CAPT STATED THAT THE MAX ALT HE OBSERVED DURING OUR TCASII DIRECTED RA MANEUVER WAS 37200 FT. CTR SAID THEY HAD NO ACFT IN THE AREA THAT CORRESPONDED TO OUR INTRUDER. TO THE BEST OF OUR KNOWLEDGE, THE TARGET DID NOT CLB WITH US, BUT WE ARE NOT SURE ON THAT. WE HAD SOME PROBS EARLY ON WITH FALSE TARGETS APPEARING ON TCASII. MOST OF THESE WERE DUE TO THE TCASII TRACKING YOUR OWN XPONDER. THESE WOULD USUALLY POP UP EXACTLY AT YOUR POS, AND FOLLOW YOUR TRACK AS WELL AS YOUR CLBS AND DSCNTS. I BELIEVE THE SOFTWARE HAS BEEN FIXED TO CURE THAT PROB. ONE OTHER SOURCE OF FALSE TARGETS I'VE HEARD OF ARE 'PARROTS,' OR ATC GND BASED XPONDERS USED TO CALIBRATE RADAR SCOPES. I WOULD EXPECT ONE OF THOSE TO REMAIN IN A STATIONARY GND LOCATION, AND NOT PASS UNDER US FROM L TO R.

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.