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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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Air carrier large transport performs an automatic altitude excursion while on autoplt and performance management system engaged. Flight crew recovers in short order and symptom fails to appear for rest of flight.
| Attributes | |
| ACN | 378000 |
| Time | |
| Date | 199708 |
| Day | Fri |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : sea |
| State Reference | WA |
| Altitude | msl bound lower : 16600 msl bound upper : 17000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zse artcc : zkc |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | cruise other descent other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : cfi pilot : flight engineer |
| Experience | flight time last 90 days : 240 flight time total : 10000 flight time type : 3000 |
| ASRS Report | 378000 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp pilot : flight engineer |
| Experience | flight time last 90 days : 200 flight time total : 8700 flight time type : 1000 |
| ASRS Report | 377918 |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance |
| Independent Detector | other flight crewa |
| Resolutory Action | aircraft : equipment problem dissipated flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation |
Narrative:
The first officer leveled off the aircraft at 17000 ft MSL with autoplt and pms engaged. Shortly after, the aircraft began an uncommanded descent. The first officer disconnected the autoplt and arrested the altitude at 16600 ft MSL, then returned to our assigned 17000 ft MSL. I feel a recurrence will be prevented by maintaining a more vigilant watch on the gauges and by investing less trust in the automation. Supplemental information from acn 377918: no explanation could be found for the uncommanded descent, the system performed normally for remainder of flight.
Original NASA ASRS Text
Title: ACR LGT PERFORMS AN AUTO ALT EXCURSION WHILE ON AUTOPLT AND PERFORMANCE MGMNT SYS ENGAGED. FLC RECOVERS IN SHORT ORDER AND SYMPTOM FAILS TO APPEAR FOR REST OF FLT.
Narrative: THE FO LEVELED OFF THE ACFT AT 17000 FT MSL WITH AUTOPLT AND PMS ENGAGED. SHORTLY AFTER, THE ACFT BEGAN AN UNCOMMANDED DSCNT. THE FO DISCONNECTED THE AUTOPLT AND ARRESTED THE ALT AT 16600 FT MSL, THEN RETURNED TO OUR ASSIGNED 17000 FT MSL. I FEEL A RECURRENCE WILL BE PREVENTED BY MAINTAINING A MORE VIGILANT WATCH ON THE GAUGES AND BY INVESTING LESS TRUST IN THE AUTOMATION. SUPPLEMENTAL INFO FROM ACN 377918: NO EXPLANATION COULD BE FOUND FOR THE UNCOMMANDED DSCNT, THE SYS PERFORMED NORMALLY FOR REMAINDER OF FLT.
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.