COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 727 Series Aeroplanes AD/B727/162 Vertical Beam Web and Forward Flange of the Aft Pressure Bulkhead Applicability: All Model 727 aircraft. 13/99 Requirement: Action in accordance with the technical requirements of FAA AD 99-18-05 Amdt 39- 11271. Note: Boeing Service Bulletins 727-53-0210 and 727-53-0055 refer. Compliance: As specified in the Requirement document for the initial and repetitive inspections, with a revised effective date of 30 December 1999. This Airworthiness Directive becomes effective on 30 December 1999. Background: The FAA received reports of fatigue cracks in the vertical beam web and forward flange of the aft pressure bulkhead. Such fatigue cracking could result in the inability of subject vertical beam to withstand the fail-safe loads, and consequent loss of cabin pressurisation.