ca-ax
Most interesting replies, thanks Lonewolf for very good links. If I could ask one more, in many of the pictures of 2 bladed co axial cabs, it appears the blade sets are not indexed, ie both discs are free wheeling, If yaw control drags one disc there has to be a de coupling of the engine torque, where does this happen in the transmission? Feel free to ignore if this question is facile, single malts do stimulate the porridge.