COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Pratt and Whitney Turbine Engines - JT9D Series AD/JT9D/30 First Stage High Pressure Turbine Disk 6/98 Applicability: Pratt and Whitney JT9D series engines incorporating high pressure turbine disks specified in FAA AD 97-25-10. Requirement: Inspect affected high pressure turbine disks in accordance with the technical requirements of FAA AD 97-25-10. Note: FAA AD 97-25-10 supersedes FAA AD 91-04-10. Compliance: Unless previously accomplished, as detailed in the Requirement document. This airworthiness directive becomes effective on 21 May 1998. Background: This Directive is prompted by reports of cracks in certain high pressure turbine disks at cooling hole and tie bolt hole locations.