SMA PLT RECEIVED FALSE INDICATION OF MARKER BEACON STARTED DSCNT TOO SOON.

Narrative

WHILE EXECUTING THE SEE LOC-D APCH; I HAD PASSED SAMOS (FAF) AND DSNDED TO 2400 FT AWAITING GRIGG (A FAN MARKER). SHORTLY AFTER LEVELING AT 2400 FT I HEARD THE AUDIO IDENT FOR GRIGG AND GOT A WHITE MARKER BEACON FLASHING LIGHT (INDICATING I WAS AT GRIGG); WHEREUPON I COMMENCED DSCNT TO 1520 FT (MDA). SEE TWR THEN ADVISED ME OF A 'LOW ALT ALERT' AND STATED THAT THE MINIMUM ALT IN MY SECTOR FOR THE APCH WAS 2400 FT. I ADVISED THAT I WAS INSIDE GRIGG AND GOING DOWN TO 1520 FT. AT THAT MOMENT I HEARD A MUCH LOUDER AUDIO IDENT FOR GRIGG AND GOT ANOTHER WHITE MARKER BEACON LIGHT (THE PREVIOUS AUDIO AND MARKER LIGHT HAD LASTED ONLY A FEW SECONDS). I CONTINUED DSCNT TO THE MDA AND; UPON TIME EXPIRATION; STARTED TO COMMENCE A MISSED APCH; WHEN I THEN BROKE OUT AND SAW THE ARPT. I CIRCLED W OF RWY 17 (AFTER MANEUVERING TO REMAIN CLR OF CLOUDS) AND LANDED RWY 17. UPON RETURN TO MY HOME BASE I HAD THE MARKER BEACONS CHKED AND NO PROB WAS FOUND. I ASSUME THAT I RECEIVED AN EARLY OR PHANTOM AUDIO AND VISUAL (MARKER LIGHT) INDICATION FOR GRIGG. MY ONLY INDICATION THAT GRIGG MAY NOT HAVE BEEN CROSSED WAS THAT THESE (AUDIO/VISUAL MARKER LIGHT) SIGNALS LASTED ONLY A FEW SECONDS; WHEREAS THE SECOND TIME I HEARD AND SAW THE INDICATIONS FOR GRIGG THE AUDIO AND VISUAL INDICATIONS WERE LOUDER/LASTED LONGER. THE LOC-D APCH; AS WELL AS SEE ARPT; ARE IN AN AREA OF HILLS WITH A FEW HIGHER PEAKS TO THE NE. PERHAPS THE TERRAIN HAD A PHANTOM/PREMATURE SIGNAL EFFECT ON RECEPTION OF THE FAN MARKER (GRIGG). IT WAS IMC WITH RAGGED LOW CEILINGS. I WOULD URGE A FLT CHK OF THIS APCH TO DETERMINE IF SUCH PREMATURE OR PHANTOM SIGNALS ARE PRESENT UNDER THE SAME CONDITIONS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: CALL TO TWR REVEALS THAT THEY ARE NOT AWARE OF ANY PROBS WITH FALSE PASSAGE OR HAVE RECEIVED ANY OTHER PLT COMPLAINTS.