COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 747 Series Aeroplanes AD/B747/183 Nacelle Strut Structure 8/98 Applicability: Model 747-100, -200, and -300 aircraft having line positions 1 through 886; excluding aircraft on which the wing/strut modification (FAA AD 95-13-07) has been accomplished; and excluding aircraft designated as Group 5 in Boeing Alert Service Bulletin 747-54A2179 Revision 2. Requirement: Action in accordance with the technical requirements of FAA AD 98-08-15 Amendment 39-10464. Note: Boeing Alert Service Bulletin 747-54A2179 Revision 2 refers. Compliance: As specified in the Requirement document with a revised effective date of 16 July 1998 for the initial and repeat inspection requirements. This airworthiness directive becomes effective on 16 July 1998. Background: The FAA received several reports of cracking of the vertical chords, midspar webs, and canted closure webs on the inboard and outboard struts of certain Model 747 series aircraft. Investigation has revealed that the cracking was due to fatigue and stress corrosion. Additionally, the investigation revealed that the cracking in the midspar webs was due to fatigue. Such fatigue cracking and stress corrosion, if not corrected, could result in failure of the strut-to-wing interface, and consequent separation of the engine and strut from the aircraft.