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Flight crew of a widebody transport descended below assigned cruise altitude due to an autothrottle problem causing 2 of the 3 engines to slowly lose power to flight idle.
| Attributes | |
| ACN | 288920 |
| Time | |
| Date | 199411 |
| Day | Sun |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : swl |
| State Reference | MD |
| Altitude | msl bound lower : 31000 msl bound upper : 35000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zdc |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : flight engineer pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 10000 |
| ASRS Report | 288920 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : flight engineer pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 5000 flight time type : 1500 |
| Events | |
| Anomaly | aircraft equipment problem : critical altitude deviation : excursion from assigned altitude other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa |
| Resolutory Action | aircraft : equipment problem dissipated controller : issued new clearance flight crew : overcame equipment problem flight crew : declared emergency |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
Narrative:
While at cruise FL310, received clearance to climb to FL350. At level off the autothrottle system slowly retarded #1 and #2 throttles to idle, unnoticed by crew. We were referencing a map and discussing geographic location. I noticed the #1 and #2 fuel flows were low and then noted the airspeed was low. I immediately initiated a recovery by adding power and descending. Copilot advised ATC immediately of descent. No traffic observed on TCASII. ATC gave clearance to FL310 and asked if we were exercising our emergency authority/authorized, to which we responded yes. Shortly after operations normal cruise at FL310 we were re-cleared to climb to FL350. Flight uneventful after incident. Autothrottle system was written up in maintenance logbook.
Original NASA ASRS Text
Title: FLC OF A WDB DSNDED BELOW ASSIGNED CRUISE ALT DUE TO AN AUTOTHROTTLE PROB CAUSING 2 OF THE 3 ENGS TO SLOWLY LOSE PWR TO FLT IDLE.
Narrative: WHILE AT CRUISE FL310, RECEIVED CLRNC TO CLB TO FL350. AT LEVEL OFF THE AUTOTHROTTLE SYS SLOWLY RETARDED #1 AND #2 THROTTLES TO IDLE, UNNOTICED BY CREW. WE WERE REFERENCING A MAP AND DISCUSSING GEOGRAPHIC LOCATION. I NOTICED THE #1 AND #2 FUEL FLOWS WERE LOW AND THEN NOTED THE AIRSPD WAS LOW. I IMMEDIATELY INITIATED A RECOVERY BY ADDING PWR AND DSNDING. COPLT ADVISED ATC IMMEDIATELY OF DSCNT. NO TFC OBSERVED ON TCASII. ATC GAVE CLRNC TO FL310 AND ASKED IF WE WERE EXERCISING OUR EMER AUTH, TO WHICH WE RESPONDED YES. SHORTLY AFTER OPS NORMAL CRUISE AT FL310 WE WERE RE-CLRED TO CLB TO FL350. FLT UNEVENTFUL AFTER INCIDENT. AUTOTHROTTLE SYS WAS WRITTEN UP IN MAINT LOGBOOK.
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.