Agusta A109E, G-HIMJ, 14 March 2004

Agusta A109E, G-HIMJ


Shortly after take-off, at approximately 300 feet, the pilot heard a whining noise which was followed by a bang. The pilot realised that something serious had occurred and landed immediately. Initial inspection revealed that the tail rotor and its control system remained intact but its drive system was no longer functional. The loss of tail-rotor drive was the result of the rotating drive shaft coming into contact with the titanium tunnel through which it passed. The lower attachment of the rear left brace assembly securing the main rotor gearbox to the aircraft structure had failed and this allowed greater than normal displacement of the upper end of the gearbox under load. This permitted sufficient misalignment of both the tail-rotor drive shaft and the engine output shafts to bring the former and one of the latter into contact. The failure of the rear left brace assembly took the form of fracture of the four bolts connecting the steel attachment bracket to the aircraft structure. The evidence is consistent with incorrect torque tightening of the bolts of the failed joint at manufacture of the aircraft. The installed bolt tension is of critical importance to the integrity of attachment between the lower brackets of the brace assemblies and the cabin structure of the 109 Series aircraft. Following this accident Agusta have reviewed the assembly process and issued revised guidance to the production team.

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