Airworthiness Directives; Turboméca S.A. ARRIEL 2B Turboshaft Engines

The FAA is superseding an existing airworthiness directive (AD) for Turbom[eacute]ca S.A. ARRIEL 2B turboshaft engines. That AD currently requires initial and repetitive inspections, cleaning, lubrication, and checks for proper operation of the hydro-mechanical unit (HMU) acceleration controller axle except on engines that incorporate modification TU 132. That AD also provides an optional terminating action for the repetitive inspections. This AD requires the same actions, but expands the applicability to include all engines that do not incorporate modification TU 149. This AD results from reports of engines with modification TU 132 incorporated experiencing stuck controller axles in the metering valve body. 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.