Narrative:

Approach control gave us a very poor setup for final approach. Very high on GS and cleared us for approach. This required unusually high rate of descent. 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 runway indicated to me I should be on or near the GS. About that time I reduced my rate of descent and we came out of clouds at approximately 1500 ft AGL and approach issued a 'low altitude alert' to us. I had the runway in sight and leveled off with a full fly down indication on my GS indicator. I asked the first officer what his GS showed, and he said 'full fly up.' his GS indicator is hidden from my view in normal seat position (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 first officer to speak up about our below GS position was big contributor to this dangerous situation. Also, mechanical failure and poor ATC handling were contributors. Easiest fix for this problem would have been to have first officer speak up when and if he noticed the anomaly.

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Original NASA ASRS Text

Title: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.