COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 727 Series Aeroplanes AD/B727/113 Aft Mount Support Fittings Engines 1 and 3 2/90 Applicability: All models. Requirement: Action in accordance with Boeing SB 727-54-0017. Note: FAA AD 89-23-17 refers. Compliance: 1. For aircraft with fittings made of 7079-T6 material. Unless previously accomplished within the last 2000 flight cycles prior to 22 February 1990 - Prior to exceeding 1000 flight cycles or 1 year after 22 February 1990, whichever occurs first, and thereafter at intervals not exceeding 3000 flight cycles. Note: 7079-T6 material is used in the aft support fitting on number 1 engine strut on aircraft line numbers 001 through 883, and number 3 engine strut on aircraft line number 001 through 880. 2. For aircraft with fittings made of 7075-T73 material. Unless previously accomplished within the last 2000 flight cycles prior to 22 February 1990 - Prior to exceeding 40,000 flight cycles, or within 1000 flight cycles after 22 February 1990 whichever occurs later, and thereafter at intervals not exceeding 3000 flight cycles. Note: 7075-T73 material is used in the aft support fitting on number 1 engine strut on aircraft line number 884 and later, and on number 3 engine strut on aircraft line number 881 and later. Background: Country of origin AD. Cracking has been reported as a result of stress corrosion and fatigue.