Action
Final rule.
Summary
We are adopting a new airworthiness directive (AD) for all Turbomeca S.A. Arriel 1A1, 1A2, 1B, 1C, 1C1, 1C2, 1D, 1D1, 1E2, 1K1, 1S, and 1S1 turboshaft engines. This AD requires performing a high gas generator speed (NG) rating vibration check. This AD was prompted by several reports of uncommanded in-flight shutdown on Arriel 1 engines. We are issuing this AD to prevent an uncommanded in- flight shutdown of the engine, which could result in an emergency landing.