To: Rob_L
While working at Hughes I was made aware of a minister that used his 300-C for cross border church purposes. On a return flight to Arizona from Mexico he mistook a river for the active runway. He landed and the tail rotor struck the water, which immediately effected the synchronization between the main rotor gearbox and the tail rotor gearbox. An Arizona National Guard UH-1 lifted him out of the water. The only obvious damage was to the tail rotor but when they pulled the gearbox off of the boom they inspected the tail rotor drive shaft. It did not shear instead it twisted which made it shorter and it pulled on the diaphragm couplings expanding them like an accordion. This placed them under tension and they pulled off of the tail rotor gearbox and the main transmission. Nothing sheared, the whole assembly just got seriously distorted.
I was not aware of the shear point on the transmission drive shaft but then again I was being paid to work on the Apache.
One strange thing, the minister sued Hughes for the damage to his helicopter, as it was his feeling that nothing should have broken. He lost.