Narrative:

We were heading as assigned (approximately 240 degrees) to intercept the localizer and to maintain 3800 ft until established on it. The heading would intercept the localizer just outside of swatt. Just prior to intercept at 3800 ft we got a GPWS warning (pull up terrain). Since it was at night, we initiated a climb and immediately advised approach control of same. At approximately 4200 ft, the warning ceased and, by 4500 ft, the climb was stopped. Apparently the 2791 ft tower (approximately 1000 ft below our intercept altitude) had set it off. Once on the ground, I talked to the approach control supervisor about the situation and he stated that we were where we were supposed to be (i.e., on the assigned heading at 3800 ft) and that the minimum vectoring altitude was in fact 3800 ft. I asked, 'then why did we get the warning?' I was told that not often, but occasionally, at 3800 ft an aircraft with a sensitive GPWS will get the warning. For obvious reasons, this is potentially dangerous situation. I would suggest a higher minimum vectoring altitude at this location to avoid similar, albeit occasional, sits in the future. Supplemental information from acn 275248: there is a small hill with a tower on it designated on the approach chart at 2791 ft MSL that I believe set off the warning. I believe that, if a base leg cannot be completed inside swatt at 3800 ft that the downwind should extend past that tower before turning base.

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Original NASA ASRS Text

Title: ACR MLG PERFORMS A MISSED APCH PROC ON THE GPWS ALERTING IN A NIGHT OP AT SAN ARPT.

Narrative: WE WERE HDG AS ASSIGNED (APPROX 240 DEGS) TO INTERCEPT THE LOC AND TO MAINTAIN 3800 FT UNTIL ESTABLISHED ON IT. THE HDG WOULD INTERCEPT THE LOC JUST OUTSIDE OF SWATT. JUST PRIOR TO INTERCEPT AT 3800 FT WE GOT A GPWS WARNING (PULL UP TERRAIN). SINCE IT WAS AT NIGHT, WE INITIATED A CLB AND IMMEDIATELY ADVISED APCH CTL OF SAME. AT APPROX 4200 FT, THE WARNING CEASED AND, BY 4500 FT, THE CLB WAS STOPPED. APPARENTLY THE 2791 FT TWR (APPROX 1000 FT BELOW OUR INTERCEPT ALT) HAD SET IT OFF. ONCE ON THE GND, I TALKED TO THE APCH CTL SUPVR ABOUT THE SIT AND HE STATED THAT WE WERE WHERE WE WERE SUPPOSED TO BE (I.E., ON THE ASSIGNED HDG AT 3800 FT) AND THAT THE MINIMUM VECTORING ALT WAS IN FACT 3800 FT. I ASKED, 'THEN WHY DID WE GET THE WARNING?' I WAS TOLD THAT NOT OFTEN, BUT OCCASIONALLY, AT 3800 FT AN ACFT WITH A SENSITIVE GPWS WILL GET THE WARNING. FOR OBVIOUS REASONS, THIS IS POTENTIALLY DANGEROUS SIT. I WOULD SUGGEST A HIGHER MINIMUM VECTORING ALT AT THIS LOCATION TO AVOID SIMILAR, ALBEIT OCCASIONAL, SITS IN THE FUTURE. SUPPLEMENTAL INFO FROM ACN 275248: THERE IS A SMALL HILL WITH A TWR ON IT DESIGNATED ON THE APCH CHART AT 2791 FT MSL THAT I BELIEVE SET OFF THE WARNING. I BELIEVE THAT, IF A BASE LEG CANNOT BE COMPLETED INSIDE SWATT AT 3800 FT THAT THE DOWNWIND SHOULD EXTEND PAST THAT TWR BEFORE TURNING BASE.

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.