Summary
We propose to adopt a new airworthiness directive (AD) for all Boeing Model 747 airplanes. This proposed AD would require a one-time inspection of certain fuselage skins at section 41 to find any external doublers that cover the inspection areas and to identify the external doublers that end on a stringer and those that do not, and related investigative and corrective actions if necessary. This proposed AD results from reports of cracks found at fastener locations in the fuselage skins at section 41. We are proposing this AD to detect and correct fuselage skin cracks at fastener locations along the skin-to- stringer attachments, which could join together and become large and consequently result in rapid decompression of the cabin.