 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
B737-800 first officer reported autopilot dropped out of VNAV and started a sharp descent on two occasions.
| Attributes | |
| ACN | 1055639 |
| Time | |
| Date | 201212 |
| Place | |
| Locale Reference | ZZZ.ARTCC |
| State Reference | US |
| Aircraft 1 | |
| Make Model Name | B737-800 |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Autopilot |
| Person 1 | |
| Function | First Officer Pilot Not Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Inflight Event / Encounter Loss Of Aircraft Control |
Narrative:
In turbulence; the pitch mode of the autopilot dropped out of VNAV path and revered to cws pitch; and the plane immediately started diving at what must have been about 4;000 FPM. Captain (PF) grabbed the yoke; and disconnected the autopilot and stopped the descent at a loss of about 300 feet. Later in the flight; the same thing happened on descent but there was no altitude deviation.
Original NASA ASRS Text
Title: B737-800 First Officer reported autopilot dropped out of VNAV and started a sharp descent on two occasions.
Narrative: In turbulence; the pitch mode of the autopilot dropped out of VNAV path and revered to CWS Pitch; and the plane immediately started diving at what must have been about 4;000 FPM. Captain (PF) grabbed the yoke; and disconnected the autopilot and stopped the descent at a loss of about 300 feet. Later in the flight; the same thing happened on descent but there was no altitude deviation.
Data retrieved from NASA's ASRS site as of July 2013 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.