Airworthiness Directives; Turbomeca S.A. Turboshaft Engines

We are superseding an existing airworthiness directive (AD) for Turbomeca S.A. Arrius 2F turboshaft engines with P3 air pipe (first section) part number (P/N) 0 319 71 918 0, installed. That AD currently requires inspections of the P3 air pipe (first section) and right-hand (RH) rear half-wall for proper clearance and readjustment of the pipe if necessary. This new AD requires the same inspections for installed engines, eliminates readjusting of the P3 air pipe (first section), requires replacement of the RH rear half-wall under certain conditions, and adds an optional terminating action. This AD was prompted by Turbomeca determining that the clearance between the P3 air pipe (first section) and the RH rear half-wall might change during installation of the engine on the helicopter. We are issuing this AD to prevent an uncommanded power loss to flight idle, which could result in an emergency autorotation landing or accident.