Air carrier X TCASII TA RA climb evasive action taken from air carrier Y. Possible system error.

Attributes
ACN	227365
Time
Date	199212
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : egpx
State Reference	FO
Altitude	msl bound lower : 29000 msl bound upper : 29000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : egpx tracon : dfw
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 4 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 29500 flight time type : 4000
ASRS Report	227365
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance non adherence : published procedure non adherence : required legal separation
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 1000 vertical : 1000
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	other

Narrative:

Cruising FL290, IMC, air carrier X under radar vector from scottish center frequency 135.85, air carrier X received TCASII TA -- noted red symbol close-in. Approximately 10 second later, received 'climb' command 1500 FPM from TCASII. Noted TCASII altitude differential at minus 700 ft. Disconnected autoplt. Turned right and started immediate climb. Spotted aircraft at 10 O'clock about 1000 ft away (IMC). Appeared to be medium large transport. Climbed to FL293 to resolve conflict. Passed above and ahead of other aircraft. Received 'clear of conflict' signal and returned to FL290 and assigned course. I do not believe we came closer than 1000 ft to the other aircraft but only because of TCASII alert.

Original NASA ASRS Text

Title: ACR X TCASII TA RA CLB EVASIVE ACTION TAKEN FROM ACR Y. POSSIBLE SYS ERROR.

Narrative: CRUISING FL290, IMC, ACR X UNDER RADAR VECTOR FROM SCOTTISH CTR FREQ 135.85, ACR X RECEIVED TCASII TA -- NOTED RED SYMBOL CLOSE-IN. APPROX 10 SEC LATER, RECEIVED 'CLB' COMMAND 1500 FPM FROM TCASII. NOTED TCASII ALT DIFFERENTIAL AT MINUS 700 FT. DISCONNECTED AUTOPLT. TURNED R AND STARTED IMMEDIATE CLB. SPOTTED ACFT AT 10 O'CLOCK ABOUT 1000 FT AWAY (IMC). APPEARED TO BE MLG. CLBED TO FL293 TO RESOLVE CONFLICT. PASSED ABOVE AND AHEAD OF OTHER ACFT. RECEIVED 'CLR OF CONFLICT' SIGNAL AND RETURNED TO FL290 AND ASSIGNED COURSE. I DO NOT BELIEVE WE CAME CLOSER THAN 1000 FT TO THE OTHER ACFT BUT ONLY BECAUSE OF TCASII ALERT.

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.