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Medium large transport flight crew in descent has autoplt trim problem and is unable to maintain altitude. When disconnecting autoplt they descend about 250 ft.
| Attributes | |
| ACN | 371142 |
| Time | |
| Date | 199706 |
| Day | Fri |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : ffu |
| State Reference | UT |
| Altitude | msl bound lower : 15750 msl bound upper : 16000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zlc tower : cou |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | descent other |
| Route In Use | arrival star : star |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : commercial |
| Experience | flight time last 90 days : 160 flight time total : 15000 flight time type : 3500 |
| ASRS Report | 371142 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument |
| Events | |
| Anomaly | altitude deviation : overshoot non adherence : clearance |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : overcame equipment problem flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation |
Narrative:
While in descent to 16000 ft MSL on autoplt, leveling at 16000 ft MSL and slowing to 250 KIAS in airspeed, autoplt was unable to trim and maintain 16000 ft MSL. As a result, the first officer disconnected the autoplt (which gave a bump due to out-of-trim) and descended about 250 ft below 16000 ft MSL in an effort to maintain passenger comfort. We corrected back to 16000 ft MSL immediately, and had no further problems.
Original NASA ASRS Text
Title: MLG FLC IN DSCNT HAS AUTOPLT TRIM PROB AND IS UNABLE TO MAINTAIN ALT. WHEN DISCONNECTING AUTOPLT THEY DSND ABOUT 250 FT.
Narrative: WHILE IN DSCNT TO 16000 FT MSL ON AUTOPLT, LEVELING AT 16000 FT MSL AND SLOWING TO 250 KIAS IN AIRSPD, AUTOPLT WAS UNABLE TO TRIM AND MAINTAIN 16000 FT MSL. AS A RESULT, THE FO DISCONNECTED THE AUTOPLT (WHICH GAVE A BUMP DUE TO OUT-OF-TRIM) AND DSNDED ABOUT 250 FT BELOW 16000 FT MSL IN AN EFFORT TO MAINTAIN PAX COMFORT. WE CORRECTED BACK TO 16000 FT MSL IMMEDIATELY, AND HAD NO FURTHER PROBS.
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.