Airworthiness Directives; Boeing Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to all Boeing Model 737-100, -200, -200C, -300, -400, and - 500 series airplanes. This AD requires repetitive inspections to detect cracking of the lower corners of the door frame and cross beam of the forward cargo door, and corrective actions, if necessary. This AD also requires eventual modification of the outboard radius of the lower corners of the door frame and reinforcement of the cross beam of the forward cargo door, which would constitute terminating action for the repetitive inspections. This amendment is prompted by reports indicating that fatigue cracks have been detected in the lower corners of the door frame and cross beam of the forward cargo door. The actions specified by this AD are intended to prevent fatigue cracking of the lower corners of the door frame and cross beam of the forward cargo door, which could result in rapid depressurization of the airplane.