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When their B737-700 was climbing out of FL380 for FL390 the flight crew discovered they were in vertical speed mode instead of nvav and the airspeed was rapidly declining into the yellow arc. The PF took over manual control to re-accelerate which resulted in the loss of approximately 1;000 feet. They then continued climb to their cleared altitude.
| Attributes | |
| ACN | 1198262 |
| Time | |
| Date | 201408 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | ZOA.ARTCC |
| State Reference | CA |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | B737-700 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Climb |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Autoflight System |
| Person 1 | |
| Function | Pilot Not Flying Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Last 90 Days 211 |
| Person 2 | |
| Function | Pilot Flying First Officer |
| Experience | Flight Crew Last 90 Days 160 |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance Deviation - Speed All Types Flight Deck / Cabin / Aircraft Event Other / Unknown |
Narrative:
Climbing thru FL380 to FL390; we noticed the aircraft getting slow. PF disconnected autopilot and pitched down three degrees to accelerate preventing stick shaker/stall. We lost at least 1;000 feet then; after accelerating; climbed back to FL390. ATC never inquired of our altitude loss nor did we see any conflicting traffic in our vicinity. Somehow we were in vs mode instead of VNAV. Neither pm or PF caught it.I believe that automation in the cockpit is taking away our scan and awareness of what the airplane is doing; I trust it too much! I also know we were tired as this was a long day; and; the last leg of the night.
Original NASA ASRS Text
Title: When their B737-700 was climbing out of FL380 for FL390 the flight crew discovered they were in Vertical Speed mode instead of NVAV and the airspeed was rapidly declining into the yellow arc. The PF took over manual control to re-accelerate which resulted in the loss of approximately 1;000 feet. They then continued climb to their cleared altitude.
Narrative: Climbing thru FL380 to FL390; we noticed the aircraft getting slow. PF disconnected autopilot and pitched down three degrees to accelerate preventing stick shaker/stall. We lost at least 1;000 feet then; after accelerating; climbed back to FL390. ATC never inquired of our altitude loss nor did we see any conflicting traffic in our vicinity. Somehow we were in VS mode instead of VNAV. Neither PM or PF caught it.I believe that automation in the cockpit is taking away our scan and awareness of what the airplane is doing; I trust it too much! I also know we were tired as this was a long day; and; the last leg of the night.
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.