WITH ONE ILS INST MALFUNCTION; A HIGH SET UP FOR THE APCH BY TRACON AND A FO RELUCTANT TO PARTICIPATE A DSCNT IS MADE BELOW GS IN IFR CONDITIONS ON FINAL TO DTW; MI.

Narrative

APCH CTL GAVE US A VERY POOR SETUP FOR FINAL APCH. VERY HIGH ON GS AND CLRED US FOR APCH. THIS REQUIRED UNUSUALLY HIGH RATE OF DSCNT. I WAS PF AND ATTEMPTED TO CAPTURE GS FROM ABOVE. MY GS DISPLAYED FULL FLY DOWN INDICATION. THIS CONTINUED UNTIL I NOTICED NO REACTION ON GS INDICATOR AND MY RANGE AND DISTANCE TO RWY INDICATED TO ME I SHOULD BE ON OR NEAR THE GS. ABOUT THAT TIME I REDUCED MY RATE OF DSCNT AND WE CAME OUT OF CLOUDS AT APPROX 1500 FT AGL AND APCH ISSUED A 'LOW ALT ALERT' TO US. I HAD THE RWY IN SIGHT AND LEVELED OFF WITH A FULL FLY DOWN INDICATION ON MY GS INDICATOR. I ASKED THE FO WHAT HIS GS SHOWED; AND HE SAID 'FULL FLY UP.' HIS GS INDICATOR IS HIDDEN FROM MY VIEW IN NORMAL SEAT POS (DOUGLAS DC9). I SAID ' THANKS A LOT FOR YOUR HELP.' MY GS INDICATOR HAD STUCK OR MALFUNCTIONED IN FULL FLY DOWN WITH NO WARNING FLAGS. FAILURE OF FO TO SPEAK UP ABOUT OUR BELOW GS POS WAS BIG CONTRIBUTOR TO THIS DANGEROUS SIT. ALSO; MECHANICAL FAILURE AND POOR ATC HANDLING WERE CONTRIBUTORS. EASIEST FIX FOR THIS PROB WOULD HAVE BEEN TO HAVE FO SPEAK UP WHEN AND IF HE NOTICED THE ANOMALY.