Airworthiness Directives; MD Helicopters Inc., Helicopters

We are adopting a new airworthiness directive (AD) for MD Helicopters, Inc. (MDHI), Model 369A, 369D, 369E, 369FF, 369HE, 369HM, 369HS, 500N, and 600N helicopters with a certain part-numbered main rotor blade attach pin (pin) installed. This AD requires ensuring the life limit of the pin as listed in the Airworthiness Limitations section of aircraft maintenance records and Instructions for Continued Airworthiness (ICA). If the hours time-in-service (TIS) of a pin is unknown, or if a pin has exceeded its life limit, this AD requires removing the affected pin from service. This AD was prompted by a report from an operator who purchased pins that did not have life limit documentation. These actions are intended to document the life limit to prevent a pin remaining in service beyond its fatigue life, which could result in failure of a pin, failure of a main rotor blade, and subsequent loss of control of the helicopter.