Airworthiness Directives; Eurocopter France Model SA-365 N1, AS-365 N2, AS-365 N3, SA-366G1, EC 155B, and EC155B1 Helicopters

This amendment supersedes an existing airworthiness directive (AD) for the specified Eurocopter France (ECF) model helicopters. That AD currently requires a onetime inspection for end play in the pitch control rod assembly double bearing (bearing) using the tail rotor (T/ R) hub control plate, and before further flight, replacing the bearing if end play is present. This amendment requires checking the T/R gearbox (TGB) oil level before the first flight of the day and maintaining the oil at the maximum level for certain helicopters. Also, this action requires, during each required inspection or at certain specified intervals, ensuring the oil is at the maximum level for certain other model helicopters. This action also requires inspecting the magnetic plug for chips at specified intervals. Depending on the quantity of chips found, this action requires either replacing the TGB before further flight or further inspecting for axial play in the T/R hub pitch change control spider (spider). If axial play is found in the spider, before further flight, this AD requires replacing the bearing. This amendment is prompted by the finding that metal chips were not detected on the magnetic plug due to insufficient oil flow because the oil in the TGB was being maintained at the minimum level. The actions specified by this AD are intended to detect metal chips on the magnetic plug, to prevent damage to the bearing resulting in end play, loss of T/R pitch control, and subsequent loss of control of the helicopter.