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The flight crew of a cargo aircraft reported a significant decrement in airspeed at the top of descent. This was attributed to an inoperative auto throttle system; auto flight mismanagement; and fatigue.
| Attributes | |
| ACN | 1307753 |
| Time | |
| Date | 201511 |
| Local Time Of Day | 1201-1800 |
| Place | |
| Locale Reference | ZZZZ.ARTCC |
| State Reference | FO |
| Environment | |
| Flight Conditions | VMC |
| Light | Dusk |
| Aircraft 1 | |
| Make Model Name | B747 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Person 1 | |
| Function | Pilot Not Flying Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Person 2 | |
| Function | Pilot Not Flying First Officer |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Deviation - Speed All Types |
Narrative:
Approaching [destination] at FL340 we were assigned a lower altitude by ATC. The auto throttles were a deferred maintenance item (dmi) and as the first officer reduced the throttles towards idle the airspeed began to decrease prior to the airplane pitching down to initiate the descent. As the airspeed approached the yellow caution ribbon I brought this to the first officer's attention. Thrust was increased; however; before this could take effect the airspeed decreased into the yellow range and we received the airspeed low annunciation. It took approximately 5-10 seconds before the additional thrust and descent restored the airspeed to the proper descent speed of 268 KTS. We were VMC in smooth air and level flight at the time so no additional 'g' load was being imposed on the aircraft.
Original NASA ASRS Text
Title: The flight crew of a cargo aircraft reported a significant decrement in airspeed at the top of descent. This was attributed to an inoperative auto throttle system; auto flight mismanagement; and fatigue.
Narrative: Approaching [destination] at FL340 we were assigned a lower altitude by ATC. The auto throttles were a Deferred Maintenance Item (DMI) and as the FO reduced the throttles towards idle the airspeed began to decrease prior to the airplane pitching down to initiate the descent. As the airspeed approached the yellow caution ribbon I brought this to the FO's attention. Thrust was increased; however; before this could take effect the airspeed decreased into the yellow range and we received the AIRSPEED LOW annunciation. It took approximately 5-10 seconds before the additional thrust and descent restored the airspeed to the proper descent speed of 268 KTS. We were VMC in smooth air and level flight at the time so no additional 'g' load was being imposed on the aircraft.
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.