Narrative:

Approximately 6 mi east of runway 25L at las perfectly established on GS for runway 25L with runway in sight (night VMC; no significant WX); received terrain caution followed by terrain pull up warning. All parameters were double-checked at the initial caution. Situational awareness showed full compliance with ILS stabilized parameters (both ILS's tuned; verified; visual) with runway showed proper 'picture' at 6 mi east of runway. Altitude was correct for that distance. All indications pointed to malfunctioning GPWS system. After evaluating all data decision was made to continue approach. Realize this is in contradiction with procedures; but weighed this against risks of rocketing up at 20 degrees nose up with emergency thrust close to airport with possible other traffic in vicinity plus other considerations that would have resulted from this emergency maneuver. Passed malfunction incident on to maintenance for the terminator and they were going to check it out. I did not write it in the book; and I believe I should have in retrospect. Called our union following morning and related incident. He was going to have GPWS unit pulled for honeywell investigation. In retrospect; we have procedures and we have guidance to evaluate the entire situation and take appropriate action. The training center has done an excellent job impressing upon us the reaction required in a pull-up situation and it is easy to armchair quarterback this one; but in reality; it was not an easy call. Perhaps I made the wrong call; but in this particular case; I believe I would probably do the same again.

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Original NASA ASRS Text

Title: A B737 GPWS ALERTED 6 NM EAST OF LAS ON THE RWY 25L ILS. THE CREW DID NOT CONDUCT THE ESCAPE MANEUVER BECAUSE THEY WERE VISUALLY CLEAR.

Narrative: APPROX 6 MI E OF RWY 25L AT LAS PERFECTLY ESTABLISHED ON GS FOR RWY 25L WITH RWY IN SIGHT (NIGHT VMC; NO SIGNIFICANT WX); RECEIVED TERRAIN CAUTION FOLLOWED BY TERRAIN PULL UP WARNING. ALL PARAMETERS WERE DOUBLE-CHKED AT THE INITIAL CAUTION. SITUATIONAL AWARENESS SHOWED FULL COMPLIANCE WITH ILS STABILIZED PARAMETERS (BOTH ILS'S TUNED; VERIFIED; VISUAL) WITH RWY SHOWED PROPER 'PICTURE' AT 6 MI E OF RWY. ALT WAS CORRECT FOR THAT DISTANCE. ALL INDICATIONS POINTED TO MALFUNCTIONING GPWS SYS. AFTER EVALUATING ALL DATA DECISION WAS MADE TO CONTINUE APCH. REALIZE THIS IS IN CONTRADICTION WITH PROCS; BUT WEIGHED THIS AGAINST RISKS OF ROCKETING UP AT 20 DEGS NOSE UP WITH EMER THRUST CLOSE TO ARPT WITH POSSIBLE OTHER TFC IN VICINITY PLUS OTHER CONSIDERATIONS THAT WOULD HAVE RESULTED FROM THIS EMER MANEUVER. PASSED MALFUNCTION INCIDENT ON TO MAINT FOR THE TERMINATOR AND THEY WERE GOING TO CHK IT OUT. I DID NOT WRITE IT IN THE BOOK; AND I BELIEVE I SHOULD HAVE IN RETROSPECT. CALLED OUR UNION FOLLOWING MORNING AND RELATED INCIDENT. HE WAS GOING TO HAVE GPWS UNIT PULLED FOR HONEYWELL INVESTIGATION. IN RETROSPECT; WE HAVE PROCS AND WE HAVE GUIDANCE TO EVAL THE ENTIRE SITUATION AND TAKE APPROPRIATE ACTION. THE TRAINING CTR HAS DONE AN EXCELLENT JOB IMPRESSING UPON US THE REACTION REQUIRED IN A PULL-UP SITUATION AND IT IS EASY TO ARMCHAIR QUARTERBACK THIS ONE; BUT IN REALITY; IT WAS NOT AN EASY CALL. PERHAPS I MADE THE WRONG CALL; BUT IN THIS PARTICULAR CASE; I BELIEVE I WOULD PROBABLY DO THE SAME AGAIN.

Data retrieved from NASA's ASRS site as of May 2009 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.