The EASA and FAA have issued new emergency Airworthiness Directives (ADs) for the Eurocopter EC135 after detection of cracks on the lower hub-shaft flange of two more of the light twins. The ADs require repetitive preflight inspections.
The EASA issued a similar emergency AD in March, after a crack was discovered on one helicopter, but the initial inspection procedure proved inadequate. Identifying deformed safety pins may not be enough, the EASA said. Therefore, pre-flight visual inspections of “the main rotor blades attachment area in the upper and lower hub-shaft flanges” are required. Also required is “visual inspection on the upper and lower hub-shaft flanges and the blade bolt area.” The main rotor hub might have to be replaced. No more than six hours should be flown between two pre-flight inspections.
The purpose of the initial and new ADs is to avoid crack propagation, which could cause hub failure. Any finding must be reported to Eurocopter. The investigation is ongoing and further ADs may follow. –T.D.