Narrative:

After takeoff and upon acceleration and clean-up at 800 ft; I noted that I had no down trim on the electric yoke trim. Queried first officer and he too had no forward trim. Only aft trim was available. I elected to maintain present speed and retain the flaps at flaps 1; 220 KTS to avoid major configuration changes which might jeopardize pitch control. ATC quickly allowed us to maintain a lower altitude and assigned a west heading so that we might assess the situation. A review of all switches and circuit breakers gave no clues. There were no cockpit (EICAS or status) messages or indications. CRM was working well with good input from both first officers. Our concern was that with only aft electric trim and no down trim we could enter an unsustainable flight condition; so we elected to operate without the autopilot; continuing to hand-fly; to preclude it trimming itself beyond its capability. While working the problem our sat phone did not work. It kept dropping off while trying to contact dispatch; going into a low priority que state. Also; the FMC kept timing out. We elected to dump fuel to landing weight and return to [our departure airport]. We slowly configured to landing; with slow speed changes. The altitude trim worked well. We asked for equipment to standby; and give a quick look to the aircraft when we exited the runway; prior to proceeding to the gate. VHF communication with tower and approach was excellent and their response was fast and most helpful. We were granted a long (20 NM) approach and slow approach speed to accommodate a gentle reconfiguration. All went well on approach and landing. During descent; the electric trim seemed to momentarily have some effect; thought the trim indicator did not follow trim input and electric nose down trim resulted in a barely discernible nose down pitch. After an uneventful landing; electric trim appeared to operate normally; with indicator following inputs in both directions. In our post flight review; there were no substantive changes we would have made to our event. Hand-flying was made easier by good crew communication and helpful input. Both first officers were exemplary in their comportment: helpful; full of good input; and steadily working the problem to its conclusion.

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Original NASA ASRS Text

Title: After takeoff both B777 yoke controlled nose down trim inputs failed; although the ALT Trim continued to function; so an emergency was declared and the flight returned to the departure airport.

Narrative: After takeoff and upon acceleration and clean-up at 800 FT; I noted that I had no down trim on the electric yoke trim. Queried First Officer and he too had no forward trim. Only aft trim was available. I elected to maintain present speed and retain the flaps at flaps 1; 220 KTS to avoid major configuration changes which might jeopardize pitch control. ATC quickly allowed us to maintain a lower altitude and assigned a west heading so that we might assess the situation. A review of all switches and circuit breakers gave no clues. There were no cockpit (EICAS or Status) messages or indications. CRM was working well with good input from both First Officers. Our concern was that with only aft electric trim and no down trim we could enter an unsustainable flight condition; so we elected to operate without the autopilot; continuing to hand-fly; to preclude it trimming itself beyond its capability. While working the problem our SAT phone did not work. It kept dropping off while trying to contact Dispatch; going into a low priority Que state. Also; the FMC kept timing out. We elected to dump fuel to landing weight and return to [our departure airport]. We slowly configured to landing; with slow speed changes. The ALT trim worked well. We asked for equipment to standby; and give a quick look to the aircraft when we exited the runway; prior to proceeding to the gate. VHF communication with Tower and Approach was excellent and their response was fast and most helpful. We were granted a long (20 NM) approach and slow approach speed to accommodate a gentle reconfiguration. All went well on approach and landing. During descent; the electric trim seemed to momentarily have some effect; thought the trim indicator did not follow trim input and electric nose down trim resulted in a barely discernible nose down pitch. After an uneventful landing; electric trim appeared to operate normally; with indicator following inputs in both directions. In our post flight review; there were no substantive changes we would have made to our event. Hand-flying was made easier by good crew communication and helpful input. Both First Officers were exemplary in their comportment: Helpful; full of good input; and steadily working the problem to its conclusion.

Data retrieved from NASA's ASRS site as of July 2013 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.