MD11 CREW HAD A GPWS 'TERRAIN; TERRAIN' WARNING WHILE BEING VECTORED IN SDF CLASS E AIRSPACE.

Narrative

WE WERE ON APCH TO LNDG AT SDF. DSNDING OUT OF 8000 FT TO 7000 FT IN CLEAN CONFIGN 237 KIAS IN HVY SNOW WITH LIGHT TURB; NIGHT IMC ON RADAR VECTORS FROM SDF APCH. WE GOT A 'TERRAIN; TERRAIN' GPWS ALERT. AS I WAS INITIATING THE ESCAPE MANEUVER; I NOTICED THE RADAR ALTIMETER INDICATING 362 FT. THE ESCAPE MANEUVER TERMINATED WITH A LEVELOFF AT 10000 FT STABILIZING AT 11000 FT. AFTER LEVELOFF; WE RPTED THE ALTDEV REQUIRED BY THE GPWS MANEUVER TO SDF APCH. APCH SAID MVA WAS 2300 FT. WE CONFIRMED THE ALTIMETER SETTING WITH ATC; XCHKED ALL INSTS AND COULD FIND NO REASON FOR THE WARNING. WE STARTED ANOTHER DSCNT. AT 4000 FT WE ACQUIRED VISUAL GND CONTACT. WE THEN RECEIVED A 'TOO LOW GEAR' WARNING. AT 4000 FT MSL (APPROX 3000 FT AGL); WE ALSO RECEIVED 4 SEPARATE 2500 FT RADAR ALT AURAL ALERTS. ON ONE OF THE ALERTS; THE FO'S RADAR ALTIMETER INDICATED 1300 FT WITH NO READING ON CAPT'S SIDE. THE REMAINDER OF APCH AND LNDG WERE UNEVENTFUL. ERRONEOUS GPWS WARNING WAS CAUSE FOR CLB ABOVE ASSIGNED ALT. SUPPLEMENTAL INFO FROM ACN 568856: SUSPECT HVY SNOW CHANGING TO HVY RAIN BELOW US SOMEHOW TRIGGERED FALSE SURFACE; OR ICE ON ANTENNA. POSSIBLE MALFUNCTION OF UNIT ALSO.