WHILE FLYING AT THE MDA WITH THE CORRECT ALTIMETER SETTING; A G3 FO RPTS A GPWS ALERT ON LOC (BACK COURSE) RWY 3R AT LUK.

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WE EXECUTED THE LOC BC RWY 3R APCH. AFTER DSNDING TO OUR MDA OF 1240 FT; WE ESTIMATED FLT VISIBILITY TO BE 2 TO 2 AND A HALF MILES WITH GND CONTACT. OUR GPWS ISSUED A TERRAIN WARNING AT THE SAME TIME TWR ISSUED A LOW ALT ALERT AND ALTIMETER SETTING. SINCE WE COULD SEE TERRAIN WITH NO OBSTRUCTIONS; WE CONTINUED; CONFIRMING WE HAD THE CORRECT ALT AND ALTIMETER SETTING. WE PICKED UP THE ARPT AND MADE A NORMAL APCH TO A NORMAL LNDG. WE QUERIED TWR WHEN ON THE GND SINCE WE HAD FLOWN THE APCH AS PUBLISHED. WE WERE TOLD THAT IT IS A COMMON OCCURRENCE FOR THAT APCH. THERE WAS NOTHING FOREWARNING US THAT THIS MAY OCCUR. HAD WE NOT HAD GND CONTACT DURING THE APCH; GPWS TERRAIN ESCAPE MANEUVER WOULD HAVE BEEN EXECUTED. THE ACFT ON APCH BEHIND US HAD THE SAME OCCURRENCE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE RATE OF DSCNT FROM THE FINAL APCH FIX TO THE MDA WAS NOT EXCESSIVE AND THAT THE ACFT HAD BEEN ESTABLISHED AT THE MDA FOR A PERIOD OF TIME PRIOR TO THE GPWS INDICATION. BECAUSE THE CREW HAD GND CONTACT THEY DID NOT EXECUTE AN ESCAPE MANEUVER IN RESPONSE TO THE WARNING. HOWEVER; THEY ALSO DID NOT SEE WHAT WOULD HAVE CAUSED A GPWS WARNING TO ACTIVATE. THE RPTR STATED AGAIN AS IN THE SUBMITTED RPT THAT THE ACFT FOLLOWING THEIRS RECEIVED THE GPWS INDICATION AND WAS ALSO TOLD BY THE TWR THAT ACFT FREQUENTLY RECEIVED FALSE INDICATIONS ON THIS APCH.