Airworthiness Directives; Boeing Model 737-100 and -200 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 737-100 and -200 series airplanes, that currently requires inspections to detect cracking of the support fittings of the Krueger flap actuator; and, if necessary, replacement of existing fittings with new steel fittings and modification of the aft attachment of the actuator. That AD also provides for an optional terminating modification that constitutes terminating action for the repetitive inspections. This amendment requires accomplishment of the previously optional terminating action. This amendment is prompted by reports of cracking due to fatigue and stress corrosion of the support fittings of the Krueger flap actuator. The actions specified by this AD are intended to prevent such cracking, which could result in fracturing of the actuator attach lugs, separation of the actuator from the support fitting, severing of the hydraulic lines, and resultant loss of hydraulic fluids. These conditions, if not corrected, could result in possible failure of one or more hydraulic systems, and consequent reduced controllability of the airplane.