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 AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/JT9D/31 and issues the following AD under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section. AD/JT9D/31 Amdt 1 14th and 15th Stage HPC Disks 8/2000 Applicability: Pratt and Whitney JT9D-59A, -70A, 7Q, -7Q3, and JT9D-7R4 series engines incorporating 14th and 15th stage high pressure compressor disks as detailed in FAA AD 98-21-22R1. Requirement: Inspect and replace as necessary 14th and 15th stage high compressor disks in accordance with the technical requirements of FAA AD 98-21-22R1. Note: P&W Alert SBs JT9D-7R4-72-524, Rev1 and A6232, Rev 2, also refer. Compliance: Initial and repeat instructions, as detailed in the Requirement document, with the effective date amended to 10 August 2000. This Airworthiness Directive becomes effective on 10 August 2000. Background: This Directive is prompted by reports of disk bore cracks detected in certain 14th and 15th stage HPC disks during engine shop visits. Such cracks could result in an uncontained engine failure and damage to the aircraft. This amendment updates the Requirement document to reference the latest revision of FAA AD 98-21-22. AD 98-21-22R1 makes reference to specific P&W NDI procedures and provides a revised definition of an engine shop visit that is less onerous than originally specified. The original issue of this AD became effective on 28 January 1999. Eugene Paul Holzapfel Delegate of the Civil Aviation Safety Authority 23 June 2000 The above AD is notified in the Commonwealth of Australia Gazette on 12 July 2000.