FLT CREW REPORTS CAPTURING FALSE GS DURING ILS RWY 8 APPROACH TO SJU. THE RPTR STATES THAT THIS IS A RECURRENT PROBLEM.

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AT 1600 FT INITIALLY CLEARED DIRECT TO WESEN. APPROACHING WESEN SJU APPROACH ASSIGNED US A 110 HEADING AND CLEARED US FOR THE APPROACH. THEY ALSO TOLD US TO SWITCH TO TOWER. IT WAS A TIGHT TURN ON; ESTIMATE A JOIN 2.5 TO 3 MILES OUTSIDE THE FAF (GS) AT 1600 FT. IT WAS DAYLIGHT AND WE HAD GROUND CONTACT; BUT THERE WERE SOME SCATTERED CLOUDS. I BELIEVE I WAS HEADS DOWN TO SWITCH TO TWR WHEN THE CAPTAIN VERBALIZED A SUSPECT THE GLIDE SLOPE. WHEN LOOKING UP I NOTICED A YELLOW LINE THROUGH GS. CAPTAIN INITIATED A CLIMB BACK TO 1600 FT; AND I CYCLED THE FDS AND RESELECTED APCH. I OBSERVED 300 FT LOW (FROM 1600 FT) AND WHILE CORRECTING TOWER INFORMED US THAT APPROACH HAD ASSIGNED US 1600 FT UNTIL ESTABLISHED ON THE APPROACH. I FLEW 3 MONTHS IN A ROW OF SJU AND FALSE GS CAPTURE IS SOMETHING I HAVE OBSERVED MULTIPLE TIMES ON ILS RWY 08. HOWEVER; WHEN I HAVE PREVIOUSLY OBSERVED FALSE GS CAPTURE WE WERE AT 3000 FT AND REMAINED IN PROTECTED AIRSPACE (ABOVE 1600 FT) WHEN THE FALSE CAPTURE OCCURRED. SINCE WE WERE ALREADY AT 1600 FT I DID NOT EXPECT A FALSE CAPTURE. I AM CONVINCED THAT THERE IS A PROBLEM WITH THE GS TO ILS RWY 08 AT SJU AND THE TECHNIQUE USED BY THE MANY OF PILOTS THAT FLY SJU A LOT IS TO ARM THE LOC FIRST AND THEN APCH WHEN YOU ARE VERY CLOSE IN.