Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to all Model 737-300, -400, and -500 series airplanes. The existing AD currently requires inspecting to determine if certain carriage spindles are installed, repetitive inspections for corrosion and indications of corrosion on affected carriage spindles, and if necessary, related investigative and corrective actions. The existing AD also provides an optional terminating action. This proposed AD would mandate the optional terminating action, which would eliminate the need for the repetitive inspections. The proposed AD results from reports of corrosion found on carriage spindles that are located on the outboard trailing edge flaps. We are proposing this AD to detect and correct corrosion of the carriage spindle, which could result in fracture. Fracture of both the inboard and outboard carriage spindles, in the forward ends through the large diameters, on a flap, could adversely affect the airplane's continued safe flight and landing.