Summary
We propose to adopt a new airworthiness directive (AD) for all Turbomeca S.A. Arriel 2B and 2B1 turboshaft engines. This proposed AD was prompted by the discovery of non-conformities of certain power turbine (PT) blade fir-tree roots. This proposed AD would require removing the affected PT blades from service on or before reaching a new reduced life limit for those certain PT blades. We are proposing this AD to prevent PT blade rupture, which could result in an uncommanded in-flight engine shutdown, forced autorotation landing, or accident.