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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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A B737-300 flight crew deviated from their assigned altitude when the autopilot altitude hold feature failed.
| Attributes | |
| ACN | 803974 |
| Time | |
| Date | 200809 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | navaid : fim.vortac |
| State Reference | CA |
| Altitude | msl single value : 37000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zla.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Experience | flight time last 90 days : 134 flight time type : 13380 |
| ASRS Report | 803974 |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : returned to assigned altitude |
| Consequence | other |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance Aircraft |
| Primary Problem | Flight Crew Human Performance |
Narrative:
Autoplt altitude hold failure with no warning or disconnect resulting in subtle altitude gain +250 ft and loss -200 ft from assigned altitude FL370. B autoplt engaged and no warning or disconnect associated with deviation/failure. An autoplt engaged and altitude hold feature also inoperative with no indication except for altitude excursions. Note: follow up call to company maintenance. Replaced stabilizer trim servo and stabilizer out of trim light assembly.
Original NASA ASRS Text
Title: A B737-300 FLT CREW DEVIATED FROM THEIR ASSIGNED ALT WHEN THE AUTOPILOT ALT HOLD FEATURE FAILED.
Narrative: AUTOPLT ALT HOLD FAILURE WITH NO WARNING OR DISCONNECT RESULTING IN SUBTLE ALT GAIN +250 FT AND LOSS -200 FT FROM ASSIGNED ALT FL370. B AUTOPLT ENGAGED AND NO WARNING OR DISCONNECT ASSOCIATED WITH DEV/FAILURE. AN AUTOPLT ENGAGED AND ALT HOLD FEATURE ALSO INOP WITH NO INDICATION EXCEPT FOR ALT EXCURSIONS. NOTE: FOLLOW UP CALL TO COMPANY MAINT. REPLACED STABILIZER TRIM SERVO AND STABILIZER OUT OF TRIM LIGHT ASSEMBLY.
Data retrieved from NASA's ASRS site as of May 2009 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.