Airworthiness Directives; Turbomeca S.A. Arriel 2B Turboshaft Engines

The FAA is revising an existing airworthiness directive (AD) for Turbomeca S.A. Arriel 2B turboshaft engines with Modification TU62A incorporated. That AD currently requires initial and repetitive inspections, cleaning, lubrication, and checks for proper operation of the HMU acceleration controller axle. This AD requires the same actions, but removes engines incorporating TU132 from the applicability and adds an optional terminating action for the repetitive actions required in AD 2005-13-25. This AD results from the engine manufacturer releasing a service bulletin to introduce modification TU132. We are issuing this AD to prevent loss of control of engine fuel flow in manual control mode or mixed control mode, which can lead to engine overspeed, and in-flight engine shutdown resulting in a forced autorotation landing or accident.