B737 Yaw damper
 

Why does the yaw damper kick off when the IRS; s are turned off

Haha, my vote for the best post of '11 ;) (IFixPlanes' post)

The slightly longer answer: The yaw damper is not a self contained system, it uses IRS attitude and acceleration data to do its job and therefore can't work without it!

Would you continue running with eyes closed? :}