Airworthiness Directives; The Boeing Company Airplanes

We propose to supersede Airworthiness Directive (AD) 2006-19- 12, which applies to certain The Boeing Model 777-200 and -300 series airplanes. AD 2006-19-12 currently requires inspecting the lower web of the aft fairing of the engine struts for any discoloration and doing any related investigative and corrective action if necessary; inspecting the heat shield castings for any damage and doing any corrective action if necessary; installing gap cover strips; and replacing insulation blankets with new insulation blankets. Since we issued AD 2006-19-12, we have received a report that an aft fairing lower spar web exceeded the allowable conductivity limits. This proposed AD would also require, depending on airplane configuration, one-time or repetitive detailed inspections for cracking and deformation, as applicable, of the aft fairing lower structure, and one-time or repetitive conductivity inspections of the aft fairing lower structure and related investigative and corrective actions if necessary. This proposed AD also adds airplanes to the applicability. We are proposing this AD to detect and correct degradation of the aft fairing lower web, which could lead to cracking of the web and could allow flammable fluids to leak into the heat shield pan castings, and consequent increased risk of an uncontained fire and subsequent structural damage.