Airworthiness Directives; The Boeing Company Airplanes

We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 747 airplanes. This AD was prompted by reports of fractured latch pins found in service; investigation revealed that the cracking and subsequent fracture were initiated by fatigue and propagated by a combination of fatigue and stress corrosion. This AD requires repetitive general visual inspections for broken or missing latch pins of the lower sills of the forward and aft lower lobe cargo doors; repetitive detailed inspections for cracking of the latch pins; and corrective actions if necessary. We are issuing this AD to detect and correct fractured or broken latch pins, which could result in a forward or aft lower lobe cargo door opening and detaching during flight, and consequent rapid decompression of the airplane.