Hi, I noticed from 2 cockpit videos that rudder trim was applied about 1/2 unit during cruise. I assume this is for a crosswind, but I though the yaw damper corrected any yawing when the autopilot was on. Is there more to rudder trim use than just flying with an engine failure? Thank you :-wave

After however many cycles these aircraft do they do tend to end up a tad bent. Most aircraft need a little trim either way in cruise to keep them wings level and going in a straight line, due to slight bending and warping of wings and fuselage. You're correct in assuming the yaw damper looks after the rudder in turns etc. Another thing about the 767 is it often needs up to 2-3 units of trim in climb, as (and this is the explanation I've heard...) different metals cool at different rates on climb, thus causing even more bending (as they shrink at different rates) until its all settled down in cruise.

Rudder trim is not used in a cross wind. lr.

Does aileron trim have to be applied also because of this bending effect? Thank you

When the autopilot is engaged use of aileron trim is prohibited, as the autopilot will hold in whatever aileron deflection is needed to hold the required heading. When manually flying then yes, airleron trim can be used, however it is not used as much as rudder trim.