Abstract:
In 2012, two EC225 helicopter ditching occurred in North Sea with no injuries. These incidents were due to the failure of the main gearbox bevel wheel. The first part of this paper presents the studies performed by Airbus Helicopters in order to identify all the contributing factors, and to reproduce in lab the phenomenon up to the failure. The main driver underlined is a specific corrosion pits phenomenon which occurred on parts not subjected to corrosion due to the main gear box oil environment. The second part of this document gives the continuing airworthiness measures put in place for aircraft flying in hostile conditions. Finally a new design has been developed and certified. This new design takes into account all the knowledge of these incidents and guaranty a high safety level. This new design is already flying for most of our oil and gas customers.