Narrative:

We were being vectored for the runway 27 localizer approach. Our position was the standard downwind vector at 5000 ft, north of and parallel to the 272 degree radial inbound course. We had deviated once to avoid a rain shower and there were more further east. Approximately 15-16 mi east of the airport we were given a right turn to a 180 degree heading (base turn). Shortly thereafter ATC turned us back to 090 degrees. He stated this was a vector outside class B airspace for inbound emergency traffic into north island NAS. I put boing LMM (NAVAID for the MSA) in the fix page and selected a 25 NM arc. This gave us a picture of the MSA limits to the east (5200 ft). I also checked the terrain on the departure area chart and noted that the terrain did in fact rise further east, but didn't appear to be dangerously high. I have flown into san a number of times in VFR conditions and felt we were safe inside the MSA at 5000 ft. Shortly before crossing the 25 NM arc ATC turned us to south to 180 degrees. While on that heading the GPWS terrain-pullup alert sounded. I initiated a hand flown climb and told the first officer to radio ATC that we were climbing due to the terrain alert. ATC at first seemed confused on our traffic call, no doubt he was also working the emergency into north island. He stated we were safe at 5000 ft and turned us toward the airport, with a 240 degree intercept heading to the localizer. By this time I had climbed to 5500 ft and the terrain warning had ceased. To say that I was agitated by the alert would be an understatement. The air carrier CFIT accident in columbia was certainly on my mind. I started a descent back to 5000 ft. At this point I was distracted (by what I still can't recall). The next transmission from ATC stated we were only cleared to 5000 ft. We were descending through 4500 ft. I immediately climbed back to 5000 ft. After getting back on altitude the rest of the approach was flown uneventfully. Contributing factors: this was my first trip after a 1 month vacation. The day had been somewhat lengthened by WX delays. There were rain showers and thunderstorms in the area. The only conclusion I can come to is that I was tired and became distracted by the 'terrain alert' and failed to maintain my situational awareness. As my first officer said, this approach had all the elements for a lesson in CFIT exposure.

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Original NASA ASRS Text

Title: AN ACR FLC RECEIVED A GPWS TERRAIN AND PULLUP WARNING IN IMC, WHILE BEING VECTORED OUTSIDE CLASS B AIRSPACE. THE FLC RESPONDED TO THE ALERT AND NOTIFIED ATC. AS THEY WERE VECTORED INBOUND, AGAIN, THE FLC INADVERTENTLY DSNDED BELOW THE CLRNC ALT. CTLED FLT TOWARD TERRAIN. ALTDEV ALT EXCURSION.

Narrative: WE WERE BEING VECTORED FOR THE RWY 27 LOC APCH. OUR POS WAS THE STANDARD DOWNWIND VECTOR AT 5000 FT, N OF AND PARALLEL TO THE 272 DEG RADIAL INBOUND COURSE. WE HAD DEVIATED ONCE TO AVOID A RAIN SHOWER AND THERE WERE MORE FURTHER E. APPROX 15-16 MI E OF THE ARPT WE WERE GIVEN A R TURN TO A 180 DEG HDG (BASE TURN). SHORTLY THEREAFTER ATC TURNED US BACK TO 090 DEGS. HE STATED THIS WAS A VECTOR OUTSIDE CLASS B AIRSPACE FOR INBOUND EMER TFC INTO NORTH ISLAND NAS. I PUT BOING LMM (NAVAID FOR THE MSA) IN THE FIX PAGE AND SELECTED A 25 NM ARC. THIS GAVE US A PICTURE OF THE MSA LIMITS TO THE E (5200 FT). I ALSO CHKED THE TERRAIN ON THE DEP AREA CHART AND NOTED THAT THE TERRAIN DID IN FACT RISE FURTHER E, BUT DIDN'T APPEAR TO BE DANGEROUSLY HIGH. I HAVE FLOWN INTO SAN A NUMBER OF TIMES IN VFR CONDITIONS AND FELT WE WERE SAFE INSIDE THE MSA AT 5000 FT. SHORTLY BEFORE XING THE 25 NM ARC ATC TURNED US TO S TO 180 DEGS. WHILE ON THAT HDG THE GPWS TERRAIN-PULLUP ALERT SOUNDED. I INITIATED A HAND FLOWN CLB AND TOLD THE FO TO RADIO ATC THAT WE WERE CLBING DUE TO THE TERRAIN ALERT. ATC AT FIRST SEEMED CONFUSED ON OUR TFC CALL, NO DOUBT HE WAS ALSO WORKING THE EMER INTO NORTH ISLAND. HE STATED WE WERE SAFE AT 5000 FT AND TURNED US TOWARD THE ARPT, WITH A 240 DEG INTERCEPT HEADING TO THE LOC. BY THIS TIME I HAD CLBED TO 5500 FT AND THE TERRAIN WARNING HAD CEASED. TO SAY THAT I WAS AGITATED BY THE ALERT WOULD BE AN UNDERSTATEMENT. THE ACR CFIT ACCIDENT IN COLUMBIA WAS CERTAINLY ON MY MIND. I STARTED A DSCNT BACK TO 5000 FT. AT THIS POINT I WAS DISTRACTED (BY WHAT I STILL CAN'T RECALL). THE NEXT XMISSION FROM ATC STATED WE WERE ONLY CLRED TO 5000 FT. WE WERE DSNDING THROUGH 4500 FT. I IMMEDIATELY CLBED BACK TO 5000 FT. AFTER GETTING BACK ON ALT THE REST OF THE APCH WAS FLOWN UNEVENTFULLY. CONTRIBUTING FACTORS: THIS WAS MY FIRST TRIP AFTER A 1 MONTH VACATION. THE DAY HAD BEEN SOMEWHAT LENGTHENED BY WX DELAYS. THERE WERE RAIN SHOWERS AND TSTMS IN THE AREA. THE ONLY CONCLUSION I CAN COME TO IS THAT I WAS TIRED AND BECAME DISTRACTED BY THE 'TERRAIN ALERT' AND FAILED TO MAINTAIN MY SITUATIONAL AWARENESS. AS MY FO SAID, THIS APCH HAD ALL THE ELEMENTS FOR A LESSON IN CFIT EXPOSURE.

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.