MVA ALT IN QUESTION AS ACR B727 RECEIVES A GPWS IN DSCNT DURING RADAR VECTORING IN A NIGHT OP.

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I WAS FLYING THE B727 ON BASE LEG FOR VECTORS TO ILS RWY 36L IN HUNTSVILLE; AL. WE WERE TOLD TO DSND TO 2800 FT MSL. PASSING THROUGH 3000 FT MSL; WE RECEIVED A GPWS ALERT WARNING OF 'TERRAIN; TERRAIN.' I IMMEDIATELY INITIATED THE PRESCRIBED PROC OF FIREWALL PWR AND PITCH TO 20 DEGS NOSE UP. THE WARNING CONTINUED FOR ABOUT 10-15 SECONDS. WHEN IT CEASED; WE LEVELED OFF AT ABOUT 5200 FT MSL AND NOTIFIED ATC. THEY STATED THAT 2800 FT MSL WAS MINIMUM VECTORING ALT AND THAT ANOTHER ACFT HAD RPTED A GPWS WARNING IN THE SAME GENERAL AREA EARLIER IN THE EVENING. IN ADDITION; GND CTL TOLD US THAT THEY HAVE HAD A HISTORY OF THESE WARNINGS IN THE SAME AREA. THIS WAS A VERY UNSETTLING FEELING DUE TO THE POOR WX CONDITIONS (IMC; ICE; NIGHT; ETC) AND THE RECENT ACCIDENT IN S AMERICA. I FELT THE ENTIRE CREW PERFORMED VERY WELL AND IN A TIMELY MANNER. I RECEIVED EXCELLENT SUPPORT THROUGHOUT THE MANEUVER FROM BOTH THE CAPT AND SO. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT GND CTLR CONFIRMED THAT THERE HAD BEEN A PRIOR GPWS EARLIER THAT EVENING; A FLT FROM THE RPTR'S COMPANY. IN FACT; THE CTLR SAID THAT THERE HAD BEEN SEVERAL OTHER EVENTS WITH GPWS DURING PREVIOUS OPS. THE TIME FRAME WAS NOT KNOWN. THE ACFT HAD TO HAVE THE ENGS INSPECTED AS THE PF HAD 'FIREWALLED' THE ENGS IN THE CLB MANEUVER; OVERTEMPING THEM IN THE PROCESS. THE ACFT WAS FERRIED BACK TO ATL THE NEXT DAY. THE ENG MANUFACTURER IS STILL STUDYING THE TAPE READOUTS FROM THE FLT DATA RECORDER TO DETERMINE STATUS OF ENGS. THE ENGS WERE OPERATED IN EXCESS PWR FOR A PERIOD OF 8 SECONDS. 'SOMEONE' FROM 'SAFETY' CALLED THE CAPT TO DISCUSS THE SIT. THE ACFT HAD ITS SPOILER-SPD BRAKES DEPLOYED. THE CREW; IN COGNIZANCE OF THE LATEST ACCIDENT IN S AMERICA; DID NOT FAIL TO REMEMBER THE ACFT'S CONFIGN AND RETRACTED THE SPOILERS ON THE MAP. SUPPLEMENTAL INFO FROM ACN 325200: THE FO WAS FLYING THE ACFT. WE WERE 24 MI SE OF ROCKET VOR AND DSNDING TO 2800 FT WHICH WAS THE INITIAL APCH ALT. WE WERE IN LIGHT RIME ICING. WING AND ENG ANTI- ICE WERE ON. PASSING THROUGH 3000 FT; WE HEARD THE GPWS WARNING; 'TERRAIN; TERRAIN.' THE FO FIREWALLED THE ENGS AND INCREASED PITCH TO 20 DEGS (UP). I NOTICED THE TA/VSI WAS PEGGED IN A CLB AND THE RADIO ALTIMETER WAS NOT SHOWING ANY READING. THE TERRAIN WARNING CONTINUED. THE SO SAID; 'KEEP IT CLBING.' PASSING THROUGH 4000-4800 FT; THE TERRAIN WARNING STOPPED. WE LEVELED OFF. DURATION OF THE WARNING WAS APPROX 30 SECONDS. (NOTE: FLT RECORDER DATA SHOWED WE WERE AT FIREWALL PWR FOR 8 SECONDS. IT SEEMED LONGER TO US.) I CALLED HUNTSVILLE APCH AND INFORMED THEM OF WHAT HAPPENED; AND WHY WE WERE AT 4800 FT. I ASKED THEM WHAT THE MINIMUM VECTORING ALT WAS IN OUR AREA. APCH REPLIED; '2800 FT.' THEY ALSO SAID THAT A B737 HAD RPTED A GPWS ALERT EARLIER IN THE EVENING IN THE SAME AREA. THE SO MADE A PA INFORMING THE PAX THAT WE HAD AN ERRONEOUS TERRAIN ALERT. THE FLT ATTENDANTS LATER SAID IT FELT LIKE A NORMAL GAR. DURING THE APCH BRIEFING; I NOTED THE TERRAIN OBSTACLES WERE TWRS LOCATED MOSTLY TO THE NE OF THE ARPT; WITH ONE 1910 FT TWR TO THE SE. ALTHOUGH WE WERE ALL CONFUSED BY A GPWS ALERT AT WHAT WE THOUGHT WAS A SAFE ALT; AN IMMEDIATE TERRAIN AVOIDANCE MANEUVER WAS INITIATED BY THE FO; AND BACKED UP BY THE SO AND I. AFTER LNDG; HUNTSVILLE GND SAID THE AREA SE OF HUNTSVILLE ARPT HAD A HISTORY OF ERRONEOUS GPWS WARNINGS.