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A B742 crew, leveling at FL320, were unable to maintain speed, requiring a 500 ft to 600 ft deviation in altitude.
| Attributes | |
| ACN | 527642 |
| Time | |
| Date | 200110 |
| Day | Sat |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | navaid : yzp.vortac |
| State Reference | BC |
| Altitude | msl bound lower : 30000 msl bound upper : 34000 |
| Environment | |
| Flight Conditions | VMC |
| Weather Elements | Turbulence |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : czvr.artcc artcc : zny.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B747-200 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | cruise : enroute altitude change |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 150 flight time total : 17500 flight time type : 1200 |
| ASRS Report | 527642 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : flight engineer pilot : atp |
| Experience | flight time last 90 days : 175 flight time total : 14000 flight time type : 3600 |
| ASRS Report | 527641 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : clearance |
| Independent Detector | other flight crewa other flight crewb other other : 3 |
| Resolutory Action | controller : issued new clearance |
| Supplementary | |
| Problem Areas | Aircraft Flight Crew Human Performance |
| Primary Problem | Flight Crew Human Performance |
Narrative:
During descent to FL320 from FL340 for turbulence avoidance, the autoplt autothrottle failed to maintain normal mach while leveling at FL320. IAS degraded aprox 20 KTS and initial stall buffet was felt. Power was advanced and autoplt disconnected, but we were unable to maintain altitude. After 500 ft to 600 ft was lost we requested and were cleared to FL300. Autoplt was reengaged in descent when airspeed recovered and level off at FL300 was normal. There was a moment of confusion at FL320 when it was not immediately clear if the problem was failure to level off or failure to maintain speed. This delayed recovery actions enough to allow a loss of about 500 ft. This may have been due to a lapse in concentration or some distraction in the cockpit. I normally rest my hand on the throttles when I expect them to move, but this may not have been done this time.
Original NASA ASRS Text
Title: A B742 CREW, LEVELING AT FL320, WERE UNABLE TO MAINTAIN SPEED, REQUIRING A 500 FT TO 600 FT DEV IN ALT.
Narrative: DURING DESCENT TO FL320 FROM FL340 FOR TURB AVOIDANCE, THE AUTOPLT AUTOTHROTTLE FAILED TO MAINTAIN NORMAL MACH WHILE LEVELING AT FL320. IAS DEGRADED APROX 20 KTS AND INITIAL STALL BUFFET WAS FELT. PWR WAS ADVANCED AND AUTOPLT DISCONNECTED, BUT WE WERE UNABLE TO MAINTAIN ALT. AFTER 500 FT TO 600 FT WAS LOST WE REQUESTED AND WERE CLRED TO FL300. AUTOPLT WAS REENGAGED IN DESCENT WHEN AIRSPEED RECOVERED AND LEVEL OFF AT FL300 WAS NORMAL. THERE WAS A MOMENT OF CONFUSION AT FL320 WHEN IT WAS NOT IMMEDIATELY CLR IF THE PROB WAS FAILURE TO LEVEL OFF OR FAILURE TO MAINTAIN SPEED. THIS DELAYED RECOVERY ACTIONS ENOUGH TO ALLOW A LOSS OF ABOUT 500 FT. THIS MAY HAVE BEEN DUE TO A LAPSE IN CONCENTRATION OR SOME DISTRACTION IN THE COCKPIT. I NORMALLY REST MY HAND ON THE THROTTLES WHEN I EXPECT THEM TO MOVE, BUT THIS MAY NOT HAVE BEEN DONE THIS TIME.
Data retrieved from NASA's ASRS site as of July 2007 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.