Summary
We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD results from mandatory continuing airworthiness information (MCAI) provided by the aviation authority of France to identify and correct an unsafe condition on Turbomeca Arrius 2F turboshaft engines. The MCAI states the following:
This AD is issued following a case of non-commanded in-flight engine shutdown which occurred on an Arrius 2F turboshaft engine, following the seizing of the gas generator. The result may be an emergency autorotation landing, or, at worst, an accident.
Investigations of this event have revealed that the seizing of the gas generator was caused by the fracture of the separator cage of the gas generator front bearing, due to high-cycle fatigue cracks initiated in the lubrication slots of the separator cage.
We are proposing this AD to prevent uncommanded shutdown of the engine, which could lead to an accident.