Summary
The FAA proposes to adopt a new airworthiness directive (AD) for Turbomeca Arriel 1B, 1D and 1D1 turboshaft engines. This proposed AD would require inspecting the 2nd stage nozzle guide vanes (NGV2) for wall thickness. This proposed AD results from one instance of a fractured 2nd stage turbine blade followed by an uncommanded engine shutdown. We are proposing this AD to detect and prevent perforation of the NGV2 that could cause fracture of a turbine blade that could result in an uncommanded engine in-flight shutdown.