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A B747 leveled off at 14000 ft with autoplt in altitude hold. Began experiencing minor altdevs. Vsi indicated 300-400 ft climb. Disconnected 'B' autoplt and aircraft pitched up. Leveled off at 14500 ft.
| Attributes | |
| ACN | 694172 |
| Time | |
| Date | 200604 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : zzzz.airport |
| State Reference | FO |
| Altitude | msl single value : 14000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B747 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : instrument pilot : commercial |
| Experience | flight time last 90 days : 57 flight time total : 15653 flight time type : 3850 |
| ASRS Report | 694172 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude |
| Independent Detector | aircraft equipment other aircraft equipment : vsi indicator other flight crewa other flight crewb |
| Resolutory Action | flight crew : returned to assigned altitude flight crew : regained aircraft control |
| Consequence | other |
| Supplementary | |
| Problem Areas | Aircraft Flight Crew Human Performance |
| Primary Problem | Aircraft |
Narrative:
First officer was PF and we had leveled at 14000 ft and autoplt 'B' engaged. We were in IMC with light; occasional chop. Autoplt was in 'altitude hold' mode and we were experiencing minor altdevs. We had been level VOR a couple of mins when vsi indicated a climb of 300-400 FPM. The first officer felt the autoplt wasn't going to catch the deviation and disconnected it. This resulted in a sharp pitch up and the vsi indicated a climb of about 600-700 FPM. The first officer immediately began to manually trim the aircraft and apply forward pressure on the yoke but we still deviated to approximately 14500 ft. First officer continued to trim the aircraft for level flight and engaged autoplt 'a' which we used for the remainder of the flight.
Original NASA ASRS Text
Title: A B747 LEVELED OFF AT 14000 FT WITH AUTOPLT IN ALT HOLD. BEGAN EXPERIENCING MINOR ALTDEVS. VSI INDICATED 300-400 FT CLB. DISCONNECTED 'B' AUTOPLT AND ACFT PITCHED UP. LEVELED OFF AT 14500 FT.
Narrative: FO WAS PF AND WE HAD LEVELED AT 14000 FT AND AUTOPLT 'B' ENGAGED. WE WERE IN IMC WITH LIGHT; OCCASIONAL CHOP. AUTOPLT WAS IN 'ALT HOLD' MODE AND WE WERE EXPERIENCING MINOR ALTDEVS. WE HAD BEEN LEVEL VOR A COUPLE OF MINS WHEN VSI INDICATED A CLB OF 300-400 FPM. THE FO FELT THE AUTOPLT WASN'T GOING TO CATCH THE DEV AND DISCONNECTED IT. THIS RESULTED IN A SHARP PITCH UP AND THE VSI INDICATED A CLB OF ABOUT 600-700 FPM. THE FO IMMEDIATELY BEGAN TO MANUALLY TRIM THE ACFT AND APPLY FORWARD PRESSURE ON THE YOKE BUT WE STILL DEVIATED TO APPROX 14500 FT. FO CONTINUED TO TRIM THE ACFT FOR LEVEL FLT AND ENGAGED AUTOPLT 'A' WHICH WE USED FOR THE REMAINDER OF THE FLT.
Data retrieved from NASA's ASRS site as of January 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.