Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Dornier Model 328-100 series airplanes. This proposal would require repetitive tests of the flight idle backup system of the propeller control system; repetitive inspections to determine the level of wear of the pins and bushings of the cam followers on the power lever rods of the engine controls; and follow-on corrective actions, if necessary. This proposal also would require eventual replacement of the power lever and condition lever rods of the engine controls with new, improved parts, which constitutes terminating action for the repetitive tests and inspections. This proposal is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by the proposed AD are intended to prevent failure of the flight idle backup system. In the event of failure of the primary propeller control system, such failure of the flight idle backup system could lead to uncommanded movement of the pitch of the propeller blade to below flight idle and into reverse thrust during flight, and consequent reduced controllability of the airplane.