Airworthiness Directives; Dornier Model 328-100 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Dornier Model 328-100 series airplanes. This amendment requires repetitive tests to detect internal leakage of hydraulic fluid within the hydraulic components of the ground spoiler system and to detect a buildup of pressure in the return line of the bypass valve, and corrective action, if necessary; installation of additional hydraulic lines and an additional hydraulic shutoff valve in the ground spoiler system; and replacement of the valve block of the ground spoiler system with a new part. This amendment also requires eventual replacement of the relief restrictor valves of the ground spoiler system with redesigned parts, which constitutes terminating action for the repetitive tests. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent the ground spoilers from unlocking and deploying during takeoff or in flight, and consequent reduced controllability of the airplane.