Following an early morning flight to Bankstown and return to Sydney, the helicopter was being prepared for a further flight. The preflight inspection had proceeded to the point where one of the crew had untied the main rotor from the stowed fore and aft position and was rotating it to the abeam position. During this procedure a restriction was noticed in the main rotor travel. Investigation revealed the restriction was caused by a partial disconnection of the tail rotor drive shaft which allowed the drive shaft to foul the drive shaft cover assembly. One nut connecting the forward disc of the drive shaft was missing from its bolt, the other nut was only finger tight. One nut at the rear disc was only finger tight, the other nut/bolt assembly was completely detached. The self locking capability of the four nuts was found to be serviceable. The helicopter had only operated 12.5 hours since extensive maintenance had been carried out on the tail rotor drive assembly.
