Good questions – as usual LEM!
When?
Boeing: During taxi when conduction the ”Before Takeoff Procedure”
Some other airlines: After engines started before taxi
How?
Boeing: Displace rudder pedals, control wheel and control column in both directions. Verify full travel, freedom of movement and controls return to center. Hold nose wheel steering wheel during rudder check to prevent nose wheel movement.
Some airline manuals also say: Move all flight controls through the full travel to ensure they operate freely. When making flight controls check slowly move all flight controls to the stop, do not slam.
Simply turn, push, pull and that's it?
I see some do it in one continuous movement through all quadrants while others go through centering several times. Boeing does not see the need to emphasize this in Pilot Manuals, Maintenance Manuals or during the Boeing Factory Pilot Courses.
Anyone else found some wise reason for a specific technique here?