AD FAA-2012-0855

We are superseding an existing airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That AD currently 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. That 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 terminates the existing repetitive inspections. This new AD revises the compliance times for the preventive modification; adds certain inspections for cracks in the number 5 cross beam of the forward cargo door; and adds inspections of the number 4 cross beam if cracks are found in the number 5 cross beam, and corrective actions if necessary. For certain airplanes, this new AD also adds a one-time inspection for airplanes previously modified or repaired, and a one-time inspection of the reinforcement angle for excessive shimming or fastener pull-up, and corrective actions if necessary. This AD was prompted by additional reports of fatigue cracking in the radius of the lower frames and in the lower number 5 cross beam of the forward cargo door. We are issuing this AD to prevent fatigue cracking of the lower corners of the door frame and number 5 cross beam of the forward cargo door, which could result in rapid depressurization of the airplane.