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First officer of an medium large transport descended prematurely below approach altitude due to a faulty GS indication.
| Attributes | |
| ACN | 308076 |
| Time | |
| Date | 199506 |
| Day | Fri |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : clt |
| State Reference | NC |
| Altitude | msl bound lower : 3000 msl bound upper : 3600 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : clt |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | descent : approach descent other |
| Route In Use | arrival other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument pilot : atp pilot : cfi |
| Experience | flight time last 90 days : 50 flight time total : 6500 flight time type : 3000 |
| ASRS Report | 308076 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : published procedure |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : became reoriented flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
The first officer was flying (myself) and was at 3600 ft and cleared for the runway 36R ILS approach at clt. Suddenly the flight director GS passed from upper scale (too low) to lower scale (too high). I started to descend to catch the GS thinking that I was too high. I stayed on the localizer the whole time. As I approached 3000 ft, I realized that the DME still read 18 mi out on the runway 36R ILS and I made an immediate climb to 3600 ft. There was an erroneous display of the GS on the flight director which led me to start a premature descent. I should have backed up raw data and DME before I started the descent. I have not flown except for 1 leg for the last 30 days prior to this flight which led me to be behind in my scan.
Original NASA ASRS Text
Title: FO OF AN MLG DSNDED PREMATURELY BELOW APCH ALT DUE TO A FAULTY GS INDICATION.
Narrative: THE FO WAS FLYING (MYSELF) AND WAS AT 3600 FT AND CLRED FOR THE RWY 36R ILS APCH AT CLT. SUDDENLY THE FLT DIRECTOR GS PASSED FROM UPPER SCALE (TOO LOW) TO LOWER SCALE (TOO HIGH). I STARTED TO DSND TO CATCH THE GS THINKING THAT I WAS TOO HIGH. I STAYED ON THE LOC THE WHOLE TIME. AS I APCHED 3000 FT, I REALIZED THAT THE DME STILL READ 18 MI OUT ON THE RWY 36R ILS AND I MADE AN IMMEDIATE CLB TO 3600 FT. THERE WAS AN ERRONEOUS DISPLAY OF THE GS ON THE FLT DIRECTOR WHICH LED ME TO START A PREMATURE DSCNT. I SHOULD HAVE BACKED UP RAW DATA AND DME BEFORE I STARTED THE DSCNT. I HAVE NOT FLOWN EXCEPT FOR 1 LEG FOR THE LAST 30 DAYS PRIOR TO THIS FLT WHICH LED ME TO BE BEHIND IN MY SCAN.
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.