Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Rolls-Royce plc (R-R) Dart series turboprop engines, that currently establishes a life limit for propeller low torque switches. This action 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 proposal is prompted by the need to add omitted part numbers and engine models to the AD. The actions specified by the proposed 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.