Airworthiness Directives; Rolls-Royce Corporation (Formerly Allison Engine Company) 250-C20 Series Turboshaft and 250-B17 Series Turboprop Engines

This amendment supersedes an emergency airworthiness directive (AD) that was sent previously to all known U.S. owners and operators of Rolls-Royce Corporation (formerly Allison Engine Company) models 250- C20, -C20B, -C20F, -C20R, -C20R/1, -C20R/2, -C20S, and -C20W turboshaft engines, and 250-B17, -B17C, -B17D, -B17E, -B17F, -B17F/1, and -B17F/2 turboprop engines by individual letters. That action required replacement of any helical torquemeter gearshaft assembly with 100 hours or less time-since-new (TSN) with a serviceable helical torquemeter gearshaft assembly, before further flight. That amendment was prompted by a report of uncontained release of power turbine blades and disk fragments caused by engine overspeed, resulting in an uncommanded engine shutdown, engine fire, and damage to the aircraft. This amendment requires the same replacement, and adds engine model - 250-C20J to the applicability section of this AD. The actions specified by this AD are intended to prevent uncontained release of power turbine blades and disk fragments caused by engine overspeed, resulting in an uncommanded engine shutdown, engine fire, and damage to the aircraft.