Action
Notice of proposed rulemaking (NPRM).
Summary
The FAA proposes to supersede an existing airworthiness directive (AD) for certain Turbomeca Arriel 1B, 1D, 1D1, and 1S1 turboshaft engines. That AD requires initial and repetitive relative position checks of the gas generator 2nd stage turbine blades on Turbomeca Arriel 1B (that incorporate Turbomeca Modification (mod) TU 148), Arriel 1D, 1D1, and 1S1 turboshaft engines that do not incorporate mod TU 347. That AD also requires initial and repetitive replacements of 2nd stage turbines on Arriel 1B, 1D, and 1D1 engines. This proposed AD would require lowering the repetitive threshold for relative position checks on Arriel 1B engines. This proposed AD would also require lowering the initial and repetitive thresholds for replacement of 2nd stage turbines on Arriel 1B, 1D, and 1D1 engines. This proposed AD results from reports of new cases of failures of 2nd stage turbine blades since we issued AD 2008-07-01. We are proposing this AD to prevent the failure of 2nd stage turbine blades, which could result in an uncommanded in-flight engine shutdown, and a subsequent forced autorotation landing or accident.