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B757-200 flight crew reported experiencing a sudden drop in airspeed while climbing through FL390 that resulted in a momentary stick shaker.
| Attributes | |
| ACN | 1411752 |
| Time | |
| Date | 201612 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | ZLC.ARTCC |
| State Reference | UT |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B757-200 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Climb |
| Flight Plan | IFR |
| Person 1 | |
| Function | Captain Pilot Not Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Person 2 | |
| Function | First Officer Pilot Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Speed All Types Inflight Event / Encounter Weather / Turbulence |
Narrative:
In climb approaching FL390 for FL410 with autopilot/autothrottles on; aircraft increased rate of climb to 6000 fpm and airspeed began to rapidly decrease with slow response by autothrottles. PF (first officer) made initial correction by decreasing rate of climb to 500 fpm via V/south on autopilot and overrode the autothrottles. When that failed to correct the airspeed and speed reached amber hook; pm disengaged autopilot/autothrottles and hand flew the aircraft by leveling for 5-10 seconds. In the process we encountered a momentary buffet (1 sec) with no other stall indications. Airspeed recovered and we re-engaged autopilot/autothrottles after all parameters recovered. No further problems noted.unsure of the cause. We later thought it might have been due to mountain wave turbulence and aircraft responding to outside conditions though no further evidence of turbulence. I think we executed proper procedures for the conditions but [maybe should] have been a little more aggressive with the corrections.
Original NASA ASRS Text
Title: B757-200 flight crew reported experiencing a sudden drop in airspeed while climbing through FL390 that resulted in a momentary stick shaker.
Narrative: In climb approaching FL390 for FL410 with autopilot/autothrottles on; aircraft increased rate of climb to 6000 fpm and airspeed began to rapidly decrease with slow response by autothrottles. PF (F/O) made initial correction by decreasing rate of climb to 500 fpm via V/S on autopilot and overrode the autothrottles. When that failed to correct the airspeed and speed reached amber hook; PM disengaged autopilot/autothrottles and hand flew the aircraft by leveling for 5-10 seconds. In the process we encountered a momentary buffet (1 sec) with no other stall indications. Airspeed recovered and we re-engaged autopilot/autothrottles after all parameters recovered. No further problems noted.Unsure of the cause. We later thought it might have been due to mountain wave turbulence and aircraft responding to outside conditions though no further evidence of turbulence. I think we executed proper procedures for the conditions but [maybe should] have been a little more aggressive with the corrections.
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.