Airworthiness Directives; Jetstream Model 4101 Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Jetstream Model 4101 airplanes, that requires installation of new case drain pipes and an additional fairlead support for the hydraulics case drain line in the rear spar area of the engine/ nacelle. This amendment is prompted by reports of fatigue failure of the case drain line in the hydraulics system. The actions specified by the proposed AD are intended to prevent the loss of main system hydraulics as a result of lack of support against vibration and subsequent fatigue failure of the case drain line for the hydraulics system.