BE90 PLT RPTS ERRATIC GS INDICATIONS ON APCH TO RWY 35R AT APA.

Narrative

ON FINAL VECTOR TO THE ILS RWY 35R APCH TO CENTENNIAL (APA) I WAS CLRED TO 9000 FT MSL UNTIL ESTABLISHED ON THE LOC. I HIT APCH MODE AND HIT ALT SELECT AND WAS COUPLED TO THE AUTOPLT AS I INTERCEPTED THE LOC AND DSNDED TO 8000 FT MSL WHICH IS THE ALT WITHIN 10 MI I NEEDED TO INTERCEPT THE LOC. AFTER REACHING 8000 FT MSL EVERYTHING SEEMED NORMAL UNTIL I RECEIVED A LOW ALT ALERT FROM THE APA TWR. I IMMEDIATELY CHKED MY ALT AND ALTIMETER SETTING AND EVERYTHING SEEMED TO BE NORMAL. AS I APCHED THE OM (CASSE) ON THE APCH I NOTICED THE GS WAS ACTING ERRATIC SHOWING VARIED UP AND DOWN MOVEMENT WITH NO GS FLAG. I PROGRESSED THROUGH THE APCH WITH VARIOUS OTHER GS VARIATIONS AND LOW ALT ALERTS FROM THE APA TWR. AFTER XING (CASSE) WITHIN A QUARTER MI I WAS ABLE TO GET A VISUAL ON THE RWY AND ARPT. ALT BOTH ON THE VASI AND GS SEEMED TO BE THE SAME AND ALTS SEEMED TO BE ON. IT SHOULD BE NOTED THAT THROUGHOUT THE APCH GS VARIATIONS WERE NOTED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT THE PROB WAS WITH THE GS RECEIVER ON HER ACFT WHICH WAS REPLACED. ACFT WAS ALLOWED TO DSND PRIOR TO REACHING OM WHICH TRIGGERED MSAW IN THE TWR.