blackhand,
I'll try a simple explanation: imagine a 'corkscrew' effect, where the aircraft is rolling and yawing at the same time. The BK117 is known for Dutch roll, due to the short moment arm of the tailrotor, and the easiest solution is to put on "opposite rudder" (yaw) to create out of balance flight. When the dutch roll damps out and becomes yaw only (almost instantaneous), feed in corrective pedal to get back into balanced flight.
BK117 is not liked by pax in the back rows, for this reason
