Narrative:

Level at 10000 ft MSL on the locke 1 arrival to sfo at locke we were vectored to a 280 degree heading to intercept the runway 19L localizer at sfo. Shortly thereafter we were cleared to descend from 10000 ft to 7000 ft. At approximately 8000 ft we received a GPWS warning 'pull up' 'too low terrain.' we accomplished our SOP emergency. Procedure (maximum power 15 degree pitch up) passing through approximately 9500 ft the warning stopped and ATC was informed of our terrain warning and climb. ATC told us the minimum vector altitude at our position was 5000 ft. He then cleared us to 7000 ft again and we experienced almost the exact same event. This time the controller told us the minimum vector altitude was 3000 ft. After further evaluation we accepted another vector to ILS runway 19L sfo and landed without event. Maintenance checked the GPWS computer and found it operational. We would not take the aircraft unless the computer was replaced as we were to fly 2 more legs in the sfo area in heavy WX. The aircraft was then taken OTS. We talked to the controller on the phone and he again assured us that we were clear of all terrain. We explained that we had to follow our procedures and climb, which he accepted. Maximum power climbs in IMC with GPWS warnings are not comfortable maneuvers. However, our training and procedure served us well. I will caution others though, that if you really know where you are (situational awareness) there may be a tendency to hesitate in this situation don't!

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Original NASA ASRS Text

Title: FALSE WARNING - ACR CREW RECEIVES A GPWS WARNING IN THE SAME GENERAL AREA TWICE. THERE IS SOME HIGH TERRAIN IN THE AREA, BUT IT WAS WELL BELOW THE NORMAL WARNING PARAMETERS.

Narrative: LEVEL AT 10000 FT MSL ON THE LOCKE 1 ARR TO SFO AT LOCKE WE WERE VECTORED TO A 280 DEG HDG TO INTERCEPT THE RWY 19L LOC AT SFO. SHORTLY THEREAFTER WE WERE CLRED TO DSND FROM 10000 FT TO 7000 FT. AT APPROX 8000 FT WE RECEIVED A GPWS WARNING 'PULL UP' 'TOO LOW TERRAIN.' WE ACCOMPLISHED OUR SOP EMER. PROC (MAX PWR 15 DEG PITCH UP) PASSING THROUGH APPROX 9500 FT THE WARNING STOPPED AND ATC WAS INFORMED OF OUR TERRAIN WARNING AND CLB. ATC TOLD US THE MINIMUM VECTOR ALT AT OUR POS WAS 5000 FT. HE THEN CLRED US TO 7000 FT AGAIN AND WE EXPERIENCED ALMOST THE EXACT SAME EVENT. THIS TIME THE CTLR TOLD US THE MINIMUM VECTOR ALT WAS 3000 FT. AFTER FURTHER EVALUATION WE ACCEPTED ANOTHER VECTOR TO ILS RWY 19L SFO AND LANDED WITHOUT EVENT. MAINT CHKED THE GPWS COMPUTER AND FOUND IT OPERATIONAL. WE WOULD NOT TAKE THE ACFT UNLESS THE COMPUTER WAS REPLACED AS WE WERE TO FLY 2 MORE LEGS IN THE SFO AREA IN HVY WX. THE ACFT WAS THEN TAKEN OTS. WE TALKED TO THE CTLR ON THE PHONE AND HE AGAIN ASSURED US THAT WE WERE CLR OF ALL TERRAIN. WE EXPLAINED THAT WE HAD TO FOLLOW OUR PROCS AND CLB, WHICH HE ACCEPTED. MAX PWR CLBS IN IMC WITH GPWS WARNINGS ARE NOT COMFORTABLE MANEUVERS. HOWEVER, OUR TRAINING AND PROC SERVED US WELL. I WILL CAUTION OTHERS THOUGH, THAT IF YOU REALLY KNOW WHERE YOU ARE (SITUATIONAL AWARENESS) THERE MAY BE A TENDENCY TO HESITATE IN THIS SIT DON'T!

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.