B757 Undifferentiated or Other Model
Flight Crew Last 90 Days 60; Flight Crew Total 12000; Flight Crew Type 4800
Distraction; Confusion; Troubleshooting
Aircraft Equipment Problem Critical
Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft
On climb in VMC conditions; Captain and I felt a noticeable left and right yawing motion of the aircraft. We had no yaw damper INOP indications or EICAS indications. We initially thought maybe an engine issue but all indications were normal. We leveled off at 17;000 FT; turned on the autopilot but condition continued. We both agreed we did not want to take an unknown flight control issue any further and returned to the departure airport. Condition continued till landing.
QRH was consulted but not relevant for the issue. Condition continued and the decision was made to return to departure airport. Told Center but did not declare an emergency. Aircraft was always controllable; but when confronted with taking an aircraft with control issues to altitude and then into a mountain airport; the decision was easier. We did attempt to call Dispatch. After informing the flight attendants and passengers the descent and uneventful landing was made. On landing sent Maintenance a message 'uncommanded yaw left and right.'
A B757 crew reported uncommanded left and right yaw motions during climb with no EICAS or other malfunction indications so as a precaution; the crew returned to the departure airport