COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 737 Series Aeroplanes AD/B737/4 Amdt 1 Side of Body Rib 2/86 Applicability: Group A: All model 737 aircraft, Line Numbers 1 to 433 plus 436 and 437. Group B: All model 737 aircraft, Line Numbers 434, 435 and 438 to 844. Requirement: Group A Aircraft: 1. FAA AD 85-01-07, Amendment 39-4983, Sections A to E. 2. Boeing SB 737-57-1087 Revision 4. Group B Aircraft: 3. FAA AD 85-22-02, Amendment 39-5159 Sections A to D. 4. Boeing SB 737-57-1137 Revision 2; or as otherwise agreed to by the Secretary. Compliance: Group A Aircraft: As detailed in Requirement Document No. 1. Group B Aircraft: As detailed in Requirement Document No. 3. Background: Cracking has been reported in the side of body rib area, in particular the rib upper chord, skin and BS 663.75 bulkhead fitting. This has been attributed to localised cyclic stresses during approach and landing. This Amendment introduces FAA AD 85-22-02 (similar to FAA AD 85-01-07) which addresses cracking in later production aircraft.