Summary
We propose to supersede an existing airworthiness directive (AD) that applies to certain The Boeing Company Model 777-200, -200LR, -300, and -300ER series airplanes. The existing AD currently requires inspecting for scribe lines in the skin along lap joints, butt joints, certain external doublers, and the large cargo door hinges, and related investigative and corrective actions if necessary. Since we issued that AD, we have determined that scribe lines could occur where external decals are installed or removed across lap joints, large cargo door hinges, or external doublers. This proposed AD would add inspecting for scribe lines where external decals have been applied or removed across lap joints, large cargo door hinges, and external doublers, and related investigative and corrective actions if necessary. We are proposing this AD to detect and correct scribe lines which can develop into fatigue cracks in the skin. Undetected fatigue cracks can grow and cause sudden decompression of the airplane.