COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 747 Series Aeroplanes AD/B747/70 Amdt 2 Nacelles/Pylons - Diagonal Brace Lugs 2/99 Applicability: Model 747 series aircraft with line positions 1 through 1046; equipped with Pratt & Whitney JT9D series engines, General Electric Model CF6-45 and -50 series engines, or Rolls Royce Model RB211 series engines; excluding those aircraft on which modifications of the strut/wing structure have been accomplished in accordance with FAA AD 95-10-16 (AD/B747/153), FAA AD 95-13-05 (AD/B747/154 Amdt 1), or FAA AD 95-13-07, as applicable. Requirement: Action in accordance with the technical requirements of FAA AD 99-01-10 Amdt 39- 10976. Note: Boeing Alert Service Bulletin 747-54A2126 Revision 5, Revision 6, and Revision 7 refer. Compliance: As specified in the Requirement Document with a revised effective date of 25 February 1999. This Amendment becomes effective on 25 February 1999. Background: Operators have reported ten diagonal brace lug cracks which are believed to initiate at lug bore corrosion pits and propagate by fatigue. Amendment 1 required new repetitive inspections to detect discrepancies of the diagonal brace lugs, and rework of the diagonal brace lug, if necessary. Since issuance of AD 89-07-15, the FAA received several reports of six additional diagonal braces with cracks in one lug of the aft clevis on the affected aircraft. Amendment 2 is issued in response to a new FAA AD which adds a requirement to repetitively inspect a new area of the diagonal brace, and for certain aircraft, adds new repetitive inspections of the subject area, while requiring that certain previously required repetitive inspections be accomplished at reduced intervals. Amendment 1 of this Airworthiness Directive became effective on 4 December 1997. The original issue of this Airworthiness Directive became effective on 10 August 1989.