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B777 captain reported encountering severe mountain wave turbulence at FL370 that resulted in speed and altitude excursions.
| Attributes | |
| ACN | 1440983 |
| Time | |
| Date | 201704 |
| Local Time Of Day | 0001-0600 |
| Place | |
| Locale Reference | ZDV.ARTCC |
| State Reference | CO |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Make Model Name | B777 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Person 1 | |
| Function | Pilot Flying Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Total 14829 Flight Crew Type 1353 |
| Events | |
| Anomaly | Deviation - Altitude Excursion From Assigned Altitude Deviation - Speed All Types Inflight Event / Encounter Weather / Turbulence |
Narrative:
While level in cruise with the autopilot and autothrottles engaged in smooth air we were at FL370 cruising at M.833-.836. The autothrottles were stable. The aircraft started climbing; the autopilot started to nose over. I reached for the throttles and pulled them back as the aircraft started to accelerate. The autopilot nosed over more. I pulled the throttles to idle and shut the autothrottles off. The overspeed warning then sounded and I shut the autopilot off and applied slight back pressure to the yoke. At this point the aircraft was climbing and still accelerating. The speed went 30 knots into the barber pole before slowing and we climbed to FL373. We descended back to FL370. Reported the severe mountain wave to ATC of +/- 35 knots and +/- 300 feet altitude. We contacted dispatch [and] told them of the severe mountain wave encounter and asked for a phone patch to [maintenance] as this was a large overspeed we wanted to ensure that we were ok to continue. [Maintenance] told us we were ok and the aircraft would be inspected in [destination airport].
Original NASA ASRS Text
Title: B777 Captain reported encountering severe mountain wave turbulence at FL370 that resulted in speed and altitude excursions.
Narrative: While level in cruise with the autopilot and autothrottles engaged in smooth air we were at FL370 cruising at M.833-.836. The autothrottles were stable. The aircraft started climbing; the autopilot started to nose over. I reached for the throttles and pulled them back as the aircraft started to accelerate. The autopilot nosed over more. I pulled the throttles to idle and shut the autothrottles off. The overspeed warning then sounded and I shut the autopilot off and applied slight back pressure to the yoke. At this point the aircraft was climbing and still accelerating. The speed went 30 knots into the barber pole before slowing and we climbed to FL373. We descended back to FL370. Reported the severe mountain wave to ATC of +/- 35 knots and +/- 300 feet altitude. We contacted Dispatch [and] told them of the severe mountain wave encounter and asked for a phone patch to [Maintenance] as this was a large overspeed we wanted to ensure that we were ok to continue. [Maintenance] told us we were ok and the aircraft would be inspected in [destination airport].
Data retrieved from NASA's ASRS site 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.