AN ACR MLG EXPERIENCED A MYSTERIOUS SERIES OF GPWS WARNINGS IN THE HSV AREA.

Narrative

DURING DSCNT FOR LNDG AT HSV; THE GPWS ANNOUNCED 'TERRAIN; TERRAIN' AND DID NOT STOP UNTIL THE ACFT WAS LEVEL WHEN IT SWITCHED TO 'LNDG GEAR' AND CONTINUED UNTIL THE GEAR WAS EXTENDED FOR LNDG. THE ACFT WAS UNDER HSV APCH; RADAR CTL; ON ABOUT A 280 DEG HDG. ALT WAS 3300 FT WITH VVI = 1000-1500 FPM AND ASSIGNED ALT 3000 FT MSL. RADIO ALT WAS APPROX 2200 FT (FIELD ELEVATION 629 FT; MINIMUM SAFE ALT = 3100 FT). NIGHT 'SEVERE CLR' CONDITIONS EXISTED AND THE WARNING WAS IGNORED; BUT NO MEANS (OTHER THAN CIRCUIT BREAKER) IS AVAILABLE TO SILENCE THE GPWS SO IT CONTINUED. THE ACFT WAS ON AUTOPLT AND CAPTURED 3000 FT NORMALLY. NO TERRAIN/OBSTACLE WAS SIGHTED. COMPLICATING THE SIT WAS AN APCH CTL QUERY ABOUT A LOW ALT ALERT IN THEIR EQUIP AS WE LEVELED AT 3000 FT. ALTIMETER SETTING WAS RECHKED WITH APCH AND IN ACFT ALTIMETERS. IN A POSTFLT PHONE CALL; THE TWR SUPVR SAID SEVERAL OTHER ACFT HAD EXPERIENCED GPWS ALERTS IN THE SAME AREA RECENTLY. THEY ALL SEEMED TO HIM TO BE THE 'MODERN' ACFT VERSUS OLDER ACFT (THE MD-80 VERSUS DC-9). HE QUESTIONED WHETHER THERE MIGHT BE SOME HIGH ENERGY RF SOURCE IN THE AREA SETTING OFF GPWS. THE CAPT THAT I FLEW WITH THE FOLLOWING WK HAD A SIMILAR EXPERIENCE IN DAY VFR THE MONTH BEFORE. THIS IS THE FIRST UNEXPLAINED GPWS ALERT I HAVE EXPERIENCED IN THE LAST SEVERAL YRS. IT COMES ON THE HEELS OF TRAINING TO REDUCE CFIT -- THE MAJOR CAUSE OF COMMERCIAL AVIATION DEATHS AS COMMERCIAL AVIATION ACCIDENT RATES CONTINUE TO DECLINE. ANY CAUSE OF FALSE ALERTS MUST BE EXPLAINED AND ELIMINATED; IF POSSIBLE; TO IMPROVE CREW RESPONSE TO 'REAL' GPWS THREATS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR IS ON THE NATIONAL SAFETY COMMITTEE FOR THE PLT'S UNION OF A MAJOR UNITED STATES ACR AND APPEARS TO BE BOTH KNOWLEDGEABLE AND CONCERNED ABOUT THIS SIT. UNFORTUNATELY; HE HAS NOT BEEN BACK TO HSV AND HAS NOT HEARD OF ANY SIMILAR INCIDENTS AT HSV OTHER THAN THE ONES LISTED IN HIS RPT.