Summary
We propose to adopt a new airworthiness directive (AD) for all Boeing Model 777 series airplanes. This proposed AD would require inspections 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. This proposed AD results from reports of scribe lines found at lap joints and butt joints, around external doublers, and at locations where external decals had been cut. 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.