Airworthiness Directives; Eurocopter France Model EC 155B and EC155B1 Helicopters

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We propose to adopt a new airworthiness directive (AD) for Eurocopter France (Eurocopter) Model EC 155B and EC155B1 helicopters that would supersede an existing AD. The airworthiness authority of France has issued a mandatory continuing airworthiness information (MCAI) AD that requires a 50 percent reduction in the life of each affected main rotor blade (blade). The MCAI also requires, for each affected blade, initial and repetitive inspections for correct alignment of the tip cap, correct tenon filler wedge (wedge) position, a crack in the tenon, and erosion in a specified zone in the end of the leading edge. Also, the MCAI requires measuring the vertical clearance between each blade assembly and a straight edge at the blade-to-tip cap junction and replacing any blade that has a cracked tenon. This proposal contains those same requirements as described in the MCAI and requires replacing any blade with a measured vertical clearance exceeding a certain limit. A misalignment, crack, or erosion in a blade could lead to failure of the blade and subsequent loss of control of the helicopter.