Narrative:

When turning on to localizer, I turned my attention to outside to look for other aircraft on approach ahead of us to to look for the runway. I kept my attention outside for, maybe, 30-40 seconds. During that time, the captain descended the airplane, west/O my being aware of it. What drew my attention back inside was the captain asking me if I had a G/south on my HSI. I didn't, then noticed that the altitude was 1100' MSL and realized the G/south was buried in the top of the case. I told him to climb and at the same time, approach control called to say they had a low altitude alert and asked us to climb immediately, which we were already in the process of doing. I told them we were correcting. We proceeded on the approach with no further problems. I asked the captain why he descended prior to G/south interception and he said he was following his G/south indicator on his ADI which we then discovered was stuck at the bottom of the case. We wrote up the instrument at the gate at boston. We critiqued the approach among ourselves at the gate and discussed the importance of xchking other instruments when flying an approach. Also discussed was the importance of xchking G/south altitude at the FAF.

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Original NASA ASRS Text

Title: CAPT FLYING LGT ILS APCH TO BOS DESCENDED BELOW GLIDE SLOPE WHEN GLIDE SLOPE INDICATOR FAILED SHOWING ACFT HIGH ON GLIDE SLOPE. APCH CTLR ADVISED HE HAD MSAW WARNING. FLT CREW CORRECTED TO PROPER ALT FOR GLIDE SLOPE.

Narrative: WHEN TURNING ON TO LOC, I TURNED MY ATTN TO OUTSIDE TO LOOK FOR OTHER ACFT ON APCH AHEAD OF US TO TO LOOK FOR THE RWY. I KEPT MY ATTN OUTSIDE FOR, MAYBE, 30-40 SECS. DURING THAT TIME, THE CAPT DSNDED THE AIRPLANE, W/O MY BEING AWARE OF IT. WHAT DREW MY ATTN BACK INSIDE WAS THE CAPT ASKING ME IF I HAD A G/S ON MY HSI. I DIDN'T, THEN NOTICED THAT THE ALT WAS 1100' MSL AND REALIZED THE G/S WAS BURIED IN THE TOP OF THE CASE. I TOLD HIM TO CLB AND AT THE SAME TIME, APCH CTL CALLED TO SAY THEY HAD A LOW ALT ALERT AND ASKED US TO CLB IMMEDIATELY, WHICH WE WERE ALREADY IN THE PROCESS OF DOING. I TOLD THEM WE WERE CORRECTING. WE PROCEEDED ON THE APCH WITH NO FURTHER PROBS. I ASKED THE CAPT WHY HE DSNDED PRIOR TO G/S INTERCEPTION AND HE SAID HE WAS FOLLOWING HIS G/S INDICATOR ON HIS ADI WHICH WE THEN DISCOVERED WAS STUCK AT THE BOTTOM OF THE CASE. WE WROTE UP THE INSTRUMENT AT THE GATE AT BOSTON. WE CRITIQUED THE APCH AMONG OURSELVES AT THE GATE AND DISCUSSED THE IMPORTANCE OF XCHKING OTHER INSTRUMENTS WHEN FLYING AN APCH. ALSO DISCUSSED WAS THE IMPORTANCE OF XCHKING G/S ALT AT THE FAF.

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.