To: vorticey
The “one way clutch” (freewheeling unit) is always between the engine and the transmission. There are design differences in the physical location but the installation is as indicated above.
The EH-101 has a fracture point on the main rotor shaft so if there is a transmission seizure the fracture point will break and the main rotor will keep turning to effect an autorotation. The tail rotor drive is above the fracture point so the tail rotor will continue to rotate at the same speed.
There is one negative point in this design in that in order to break the fracture point the kinetic energy of the rotor system must be used to effect the fracture and in doing so the dampers will most likely be severely damaged. This will result in loads that were not designed for in the elastomeric bearings in the rotorhead causing them to possibly fail resulting in a crash.