Victor India,
You write, "If an accident occurred in the takeoff or landing phase, even if it was unrelated to the lack of yaw damper, I for one would not like to explain why I was contravening the Operating Manual, perhaps risking my job or the insurance."
The point is as mentioned in the Limitations Chapter of the AFM;
"On aircraft 45-002 thru 45-225 NOT modified by SB 45-55-6, the yaw damper must be engaged for all flight operations except take-off and landing."
"On aircraft 25-226 and subsequent and prior aircraft modified by SB 45-55-6, yaw damper use is not required."
Clearly the yaw damper is not required for landing and that is why many operators turn it off in accordance with the Lear 40/45 Flight Controls System Chapter issued by Flight Safety. Those who leave it on struggle with the undesired yaw damper feedback and in my opinion are creating a potential for serious problems during the landing and rollout.
regards,
Bruce Waddington