An air carrier widebody transport climbed in response to a false TCASII warning.

Attributes
ACN	258539
Time
Date	199312
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : pol
State Reference	FO
Altitude	msl bound lower : 28000 msl bound upper : 28500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : egtt
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 3 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer pilot : cfi
Experience	flight time last 90 days : 180 flight time total : 14000 flight time type : 700
ASRS Report	258539
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 0 vertical : 1000
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

We were in level cruise flight at FL280 in london center's airspace flying a widebody transport. TCASII sounded a TA and a TCASII target appeared on our scope that was previously not there. The target showed at our immediate 12 O'clock and less than 1 mi. After about 2 seconds, the TCASII switched to an RA which commanded a 1500 FPM climb. I grabbed the yoke and immediately initiated the climb. Out of about FL285 I saw the other aircraft passing below and to the left away from us. I stopped climbing and began a descent back to FL280. The other aircraft appeared to have been at FL270, and was never a conflict. London center verified this when I contacted them to report the event. I presume this was a false TCASII warning, but the system tested normally and appeared to function normally for the duration of the flight.

Original NASA ASRS Text

Title: AN ACR WDB CLBED IN RESPONSE TO A FALSE TCASII WARNING.

Narrative: WE WERE IN LEVEL CRUISE FLT AT FL280 IN LONDON CTR'S AIRSPACE FLYING A WDB. TCASII SOUNDED A TA AND A TCASII TARGET APPEARED ON OUR SCOPE THAT WAS PREVIOUSLY NOT THERE. THE TARGET SHOWED AT OUR IMMEDIATE 12 O'CLOCK AND LESS THAN 1 MI. AFTER ABOUT 2 SECONDS, THE TCASII SWITCHED TO AN RA WHICH COMMANDED A 1500 FPM CLB. I GRABBED THE YOKE AND IMMEDIATELY INITIATED THE CLB. OUT OF ABOUT FL285 I SAW THE OTHER ACFT PASSING BELOW AND TO THE L AWAY FROM US. I STOPPED CLBING AND BEGAN A DSCNT BACK TO FL280. THE OTHER ACFT APPEARED TO HAVE BEEN AT FL270, AND WAS NEVER A CONFLICT. LONDON CTR VERIFIED THIS WHEN I CONTACTED THEM TO RPT THE EVENT. I PRESUME THIS WAS A FALSE TCASII WARNING, BUT THE SYS TESTED NORMALLY AND APPEARED TO FUNCTION NORMALLY FOR THE DURATION OF THE FLT.

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.