Airworthiness Directives; Turbomeca Arriel 1B, 1D, 1D1, and 1S1 Turboshaft Engines

The FAA is revising an existing airworthiness directive (AD) for certain Turbomeca Arriel 1B, 1D, 1D1, and 1S1 turboshaft engines. That AD currently requires initial and repetitive position checks of the gas generator 2nd stage turbine blades on all Turbomeca Arriel 1B, 1D, 1D1, and 1S1 turboshaft engines. That AD also currently requires initial and repetitive replacements of 2nd stage turbines on 1B, 1D, and 1D1 engines only. This AD revision requires the same actions, but would relax the compliance times for initially replacing 2nd stage turbines in Arriel 1B, 1D, and 1D1 turboshaft engines. We are issuing this AD revision to clarify and relax the AD compliance times for 2nd stage turbine initial replacement on Arriel 1B, 1D, and 1D1 turboshaft engines. We are also issuing this AD revision to prevent in-flight engine shutdown and subsequent forced autorotation landing or accident.