The name supposedly comes because is seems like the motion of a speed skater,
Mmmmm it is the motion of two skaters arm in arm moving forward.
John Eacott
I was sitting on top of a BK117 looking rearward at the offset of the vertical stabs. When questioned the pilot(high time) said it(the offset) assisted to prevent dutch roll. This sent me on a search about dutch roll and spiral dive in helicopters.
The explanations I have found about the phenomenom in helicopters is very technical, involve angle of attack of MR, forward airspeed and relationship with TR torque.
The fact that a MR has dihedral was enlightening to say the least.
Thanks for the Readers Digest version.
Blackhand