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A B777 horizontal trim was inoperative when operated from the yoke trim switches during climb but operated normally from the alt stab trim levers. At cruise the yoke trim switch's input was normal but in the descent for landing the yoke switches again became intermittent. A horizontal trim tab ace was changed.
| Attributes | |
| ACN | 918699 |
| Time | |
| Date | 201011 |
| Local Time Of Day | 1201-1800 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | B777-200 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Climb |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Horizontal Stabilizer Control |
| Person 1 | |
| Function | First Officer Pilot Flying |
| Experience | Flight Crew Last 90 Days 250 Flight Crew Total 16400 Flight Crew Type 8800 |
| Person 2 | |
| Function | Pilot Not Flying Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Last 90 Days 189 Flight Crew Total 19000 Flight Crew Type 4000 |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical |
Narrative:
While climbing out; at about 1;000 ft; I called for flap retraction when I noticed that excessive forward trim was required. I mentioned this to the captain. A few thousand feet higher I still required forward pressure on the yoke to maintain my desired pitch attitude. While trimming; I looked at the stab trim setting and the indicator wasn't moving. Next I used the alternate stab trim levers on the center console and was able to adequately trim the aircraft. I mentioned this to the captain and suggested he attempt trimming from his side. Initially he couldn't trim from the the yoke trim switches either. Eventually the yoke trim switch did start functioning again after using the alternate stab trim levers. After consulting with dispatch; maintenance; and amongst ourselves over the systems; we continued to our planned destination. We checked every hour to ensure the yoke trim worked. At top of descent the trim was checked and worked but at about 8;000 ft the trim worked intermittently again. On final; the trim worked normally.
Original NASA ASRS Text
Title: A B777 horizontal trim was inoperative when operated from the yoke trim switches during climb but operated normally from the Alt Stab Trim Levers. At cruise the yoke trim switch's input was normal but in the descent for landing the yoke switches again became intermittent. A horizontal trim tab ACE was changed.
Narrative: While climbing out; at about 1;000 FT; I called for flap retraction when I noticed that excessive forward trim was required. I mentioned this to the Captain. A few thousand feet higher I still required forward pressure on the yoke to maintain my desired pitch attitude. While trimming; I looked at the stab trim setting and the indicator wasn't moving. Next I used the Alternate Stab Trim levers on the center console and was able to adequately trim the aircraft. I mentioned this to the Captain and suggested he attempt trimming from his side. Initially he couldn't trim from the the yoke trim switches either. Eventually the yoke trim switch did start functioning again after using the Alternate Stab Trim Levers. After consulting with Dispatch; Maintenance; and amongst ourselves over the systems; we continued to our planned destination. We checked every hour to ensure the yoke trim worked. At top of descent the trim was checked and worked but at about 8;000 FT the trim worked intermittently again. On final; the trim worked normally.
Data retrieved from NASA's ASRS site as of April 2012 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.