A B757 received a TCASII RA while on approach to dfw.

Attributes
ACN	433175
Time
Date	199903
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : dfw.airport
State Reference	TX
Altitude	msl bound lower : 3000 msl bound upper : 4700
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : dfw.tower
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 295
Route In Use	approach : instrument precision
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tower : dfw.tower
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 250 flight time total : 18000 flight time type : 1800
ASRS Report	433175
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne critical non adherence : published procedure
Independent Detector	aircraft equipment : tcas other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : took precautionary avoidance action
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

At 1 mi south of ILS runway 36L final fix, a TCASII RA sounded with a climb command. The RA target was a 'pop-up' at our altitude of 3000 ft MSL. During the evasive climb, there was no vertical separation indicated, so I increased the climb attitude and rate as I assumed the target was climbing also. After 1200 ft of climb, the first officer stated the target symbol altitude changed to a -1500 ft indication. I stopped the climb at 4700 ft MSL. The dfw tower was advised of the RA as I began the evasive climb. We got vectors for a second approach and a normal arrival. I believe the RA event was either a software glitch or a spurious computer anomaly. I tracked the localizer course during the climb and do not believe safety of the dfw airspace was compromised. The 'pop-up' nature of the event was startling as there was no white or yellow symbol preceding the red RA symbol.

Original NASA ASRS Text

Title: A B757 RECEIVED A TCASII RA WHILE ON APCH TO DFW.

Narrative: AT 1 MI S OF ILS RWY 36L FINAL FIX, A TCASII RA SOUNDED WITH A CLB COMMAND. THE RA TARGET WAS A 'POP-UP' AT OUR ALT OF 3000 FT MSL. DURING THE EVASIVE CLB, THERE WAS NO VERT SEPARATION INDICATED, SO I INCREASED THE CLB ATTITUDE AND RATE AS I ASSUMED THE TARGET WAS CLBING ALSO. AFTER 1200 FT OF CLB, THE FO STATED THE TARGET SYMBOL ALT CHANGED TO A -1500 FT INDICATION. I STOPPED THE CLB AT 4700 FT MSL. THE DFW TWR WAS ADVISED OF THE RA AS I BEGAN THE EVASIVE CLB. WE GOT VECTORS FOR A SECOND APCH AND A NORMAL ARR. I BELIEVE THE RA EVENT WAS EITHER A SOFTWARE GLITCH OR A SPURIOUS COMPUTER ANOMALY. I TRACKED THE LOC COURSE DURING THE CLB AND DO NOT BELIEVE SAFETY OF THE DFW AIRSPACE WAS COMPROMISED. THE 'POP-UP' NATURE OF THE EVENT WAS STARTLING AS THERE WAS NO WHITE OR YELLOW SYMBOL PRECEDING THE RED RA SYMBOL.

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.