Airworthiness Directives; Turbomeca Arriel 2B Series Turboshaft Engines

The FAA is adopting a new airworthiness directive (AD) for Turbomeca Arriel 2B, 2B1, and 2B1A turboshaft engines. This AD requires visually inspecting the splines of the high-pressure (HP) pump drive gear shaft and coupling shaft assembly for wear. This AD results from reports of uncommanded in-flight shutdowns of engines. We are issuing this AD to detect wear on the splines of the HP pump drive gear shaft and coupling shaft assembly, which could interrupt the fuel flow and cause an uncommanded in-flight shutdown of the engine on a single- engine helicopter. The in-flight shutdown of the engine could result in a forced autorotation landing or accident.