Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Fokker Model F.28 Mark 1000, 2000, 3000, and 4000 series airplanes, that currently requires an inspection to detect free movement of the actuator servo- valve sub-assembly of the horizontal stabilizer actuator, and replacement, if necessary. This action would add a one-time inspection to determine the residual strength of the servo-valve sub-assembly of the horizontal stabilizer actuator, and replacement of the actuator with a new or serviceable actuator, if necessary; and eventual replacement of the horizontal stabilizer actuator with an improved actuator. 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 uncommanded trimming or failure of the trim system of the horizontal stabilizer, and consequent reduced controllability of the airplane.