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An unexplained deviation from altitude in autoflt is overcome by an autoplt disconnect and a climb back to the assigned altitude.
| Attributes | |
| ACN | 507720 |
| Time | |
| Date | 200104 |
| Day | Thu |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : zbw.artcc |
| State Reference | NH |
| Altitude | msl single value : 35000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B757 Undifferentiated or Other Model |
| Flight Phase | climbout : intermediate altitude |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : cfi pilot : atp pilot : multi engine |
| Experience | flight time last 90 days : 200 flight time total : 12000 flight time type : 1150 |
| ASRS Report | 507720 |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance |
| Resolutory Action | flight crew : overrode automation flight crew : returned to assigned altitude |
| Supplementary | |
| Problem Areas | Aircraft |
| Primary Problem | Aircraft |
Narrative:
Phase: VNAV and autoplt engaged to FL350/climb. Deviation: upon reaching FL350, 2 chimes were heard. Plane started a descent. Autoplt was disengaged to correct and return to FL350. Altitude deviation to FL345.5 was observed. There was no ATC questioning. Flight proceeded with no further problem. Autoplt was re-engaged.
Original NASA ASRS Text
Title: AN UNEXPLAINED DEV FROM ALT IN AUTOFLT IS OVERCOME BY AN AUTOPLT DISCONNECT AND A CLB BACK TO THE ASSIGNED ALT.
Narrative: PHASE: VNAV AND AUTOPLT ENGAGED TO FL350/CLB. DEV: UPON REACHING FL350, 2 CHIMES WERE HEARD. PLANE STARTED A DSCNT. AUTOPLT WAS DISENGAGED TO CORRECT AND RETURN TO FL350. ALTDEV TO FL345.5 WAS OBSERVED. THERE WAS NO ATC QUESTIONING. FLT PROCEEDED WITH NO FURTHER PROB. AUTOPLT WAS RE-ENGAGED.
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.