Airworthiness Directives; Rolls-Royce Limited Dart Series Turboprop Engines

This amendment supersedes an existing airworthiness directive (AD), applicable to Rolls-Royce Limited (R-R) Dart series turboprop engines, that currently establishes a life limit for propeller low torque switches. This amendment adds two propeller low torque switch part numbers and two R-R Dart engine models that were omitted from the current AD, and establishes a calendar end-date for removal of propeller low torque switches from service. This amendment is prompted by the need to add omitted part numbers and engine models to the AD. The actions specified by this AD are intended to prevent cracking of the snap diaphragm in the propeller low torque switch, which could delay propeller auto-feathering and thereby adversely affect aircraft controllability.