Narrative:

After being taken off our first approach due to inadequate spacing with preceding traffic we were given extensive vectors to an ILS runway 24R at lax. We finally joined the localizer at an assigned altitude of 2500 ft MSL approximately 25 NM from the airport. Shortly after that, our GPWS activated with the warning 'terrain' (mode 2). I immediately applied takeoff go around thrust and began a climb. When the warning ceased I leveled the aircraft at 3500 ft MSL. We told ATC of our GPWS climb and he stated that terrain should not have been a factor for us. I immediately descended back to 2500 ft MSL while the captain confirmed with ATC that this is what they wanted us to do. We were still on the localizer and we were reclred for the approach to runway 24R. The captain later stated that he saw a reading of approximately 1300 ft on the radar altimeter right after the GPWS activated. Later close examination of the commercial approach chart for ILS runway 24R at lax reveals a terrain feature approximately 21 NM from lax under the 24R localizer with a marked elevation of 1388 ft MSL. This terrain may have been the cause of our GPWS activation. GPWS pull-ups in crowded airspace (GPWS takes priority over TCASII) are hazardous and ATC should be aware of terrain features in their area which may trigger these events.

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Original NASA ASRS Text

Title: GPWS CAUSES ACFT TO CLB 1000 FT DURING APCH.

Narrative: AFTER BEING TAKEN OFF OUR FIRST APCH DUE TO INADEQUATE SPACING WITH PRECEDING TFC WE WERE GIVEN EXTENSIVE VECTORS TO AN ILS RWY 24R AT LAX. WE FINALLY JOINED THE LOC AT AN ASSIGNED ALT OF 2500 FT MSL APPROX 25 NM FROM THE ARPT. SHORTLY AFTER THAT, OUR GPWS ACTIVATED WITH THE WARNING 'TERRAIN' (MODE 2). I IMMEDIATELY APPLIED TKOF GAR THRUST AND BEGAN A CLB. WHEN THE WARNING CEASED I LEVELED THE ACFT AT 3500 FT MSL. WE TOLD ATC OF OUR GPWS CLB AND HE STATED THAT TERRAIN SHOULD NOT HAVE BEEN A FACTOR FOR US. I IMMEDIATELY DSNDED BACK TO 2500 FT MSL WHILE THE CAPT CONFIRMED WITH ATC THAT THIS IS WHAT THEY WANTED US TO DO. WE WERE STILL ON THE LOC AND WE WERE RECLRED FOR THE APCH TO RWY 24R. THE CAPT LATER STATED THAT HE SAW A READING OF APPROX 1300 FT ON THE RADAR ALTIMETER RIGHT AFTER THE GPWS ACTIVATED. LATER CLOSE EXAMINATION OF THE COMMERCIAL APCH CHART FOR ILS RWY 24R AT LAX REVEALS A TERRAIN FEATURE APPROX 21 NM FROM LAX UNDER THE 24R LOC WITH A MARKED ELEVATION OF 1388 FT MSL. THIS TERRAIN MAY HAVE BEEN THE CAUSE OF OUR GPWS ACTIVATION. GPWS PULL-UPS IN CROWDED AIRSPACE (GPWS TAKES PRIORITY OVER TCASII) ARE HAZARDOUS AND ATC SHOULD BE AWARE OF TERRAIN FEATURES IN THEIR AREA WHICH MAY TRIGGER THESE EVENTS.

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.