Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 747-200B, 747-200C, 747-200F, 747-300, and 747SR series airplanes. This proposed AD would require doing repetitive inspections of engine struts 1 through 4, as applicable, for heat discoloration, cracking, buckling, or wrinkling. This proposed AD also would require a conductivity test to detect the extent of the heat damage and an inspection to detect cracking of the heat-discolored, buckled, or wrinkled area; and repair; if necessary. This proposed AD results from reports of heat damage and cracking of the skin and internal structure adjacent to and aft of the precooler exhaust vent on several engine struts. We are proposing this AD to detect and correct cracking, buckling, wrinkling, or heat damage of the skin and internal structure of the engine struts, which could result in extensive damage to the engine struts and consequent possible separation of an engine from the airplane during flight.