GPWS 'TERRAIN' ALERT. FLC CLBED AS PRESCRIBED. CHARTS DON'T SHOW ANY PEAKS WITHIN 1000 FT OF 6000 FT IN THAT AREA. CAUSE OF ALERT UNKNOWN; BUT IT HAS HAPPENED BEFORE. PERHAPS; THE FACT THAT 8000 FT IS BOSTON AIRSPACE; THE MINIMUM ENRTE ON THAT AIRWAY WOULD BE BETTER TO BE AT 8000 FT.

Narrative

FLT WAS BEING VECTORED BY TRACON; LEVEL AT ASSIGNED ALT OF 6000 FT; WITH CURRENT ALTIMETER SETTING. CREW OBSERVED RED GPWS WARNING LIGHT ILLUMINATED; ACCOMPANIED BY AURAL WARNING 'TERRAIN; TERRAIN.' CAPT (PF) IMMEDIATELY APPLIED GAR PWR; DISCONNECTED AUTOPLT AND BEGAN SMART CLB. FO ADVISED ATC OF REASON FOR ALT EXCURSION AS ACFT LEVELED AT APPROX 8000 FT. WITH AGREEMENT OF ATC DSNDED TO 6000 FT AND CONTINUED TO SWF WITH UNEVENTFUL APCH AND LNDG. IN DISCUSSION WITH TRACON SUPVR ON THE PHONE; ADVISED THIS HAS HAPPENED BEFORE; ONLY WITH S80 ACFT. HIS MAIN CONCERN IS THAT HE DOES NOT OWN THE AIRSPACE AND THAT IN THE CLB WE HAD ENTERED THE AIRSPACE OF ZBW. A JUMP SEAT RIDER WHO LIVES IN THE AREA SAID HE HAD SEEN IT HAPPEN BEFORE; AND INDICATED THERE MAY BE A PEAK ON THE RIDGE WHICH MAY HAVE TRIGGERED THE WARNING. ATC ADVISED MINIMUM SAFE VECTORING ALT IN THE AREA WAS 5700 FT. THE CREW FOLLOWED APPROPRIATE PROCS IN RESPONSE TO THIS CRITICAL WARNING AND THIS WAS ACKNOWLEDGED BY TRACON; BUT PROB REMAINS. NO LOSS OF SEPARATION NOTED; NO VIOLATIONS OR OTHER ACTION EXPECTED.