French civil aviation authority DGAC has issued emergency airworthiness directives on the Eurocopter EC120B and AS355. Inspection is required to prevent possible tailrotor drive failure on the EC120B, and to prevent engine automatic shutdown caused by overspeed in the case of some AS355s.
Scoring in the tailrotor drive tube has been discovered in an EC120B, caused by incorrect drive-shaft damper positioning. Eurocopter has advised the DGAC of a case of main gear box free-wheel slippage with resulting engine shutdown due to overspeed, which occurred in an AS355 during the single-engine phase of an acceptance flight at its Marignane, France base.
Some AS355s recently fitted with a new gear box bevel reduction gear or combiner, or that have had one recently overhauled, should not be flown without reference to Eurocopter's alert telex.
Source: Flight International
