COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES AlliedSignal (Lycoming) Turbine Engines - ALF502 and LF507 Series AD/ALF/11 Amdt 1 Third Stage Compressor Disc 8/91 Applicability: All ALF502 engines fitted with third stage compressor disc part number 2-101-630- 04/-05. Requirement: Inspect third stage compressor discs part number 2-101-630-04/-05 for evidence of cracking and apply Sermetel W or ALSEAL 518 protective coating in accordance with; (a) Model ALF502R series engines: Lycoming SB ALF502R 72-203 R2, or (b) Model ALF502L series engines: Lycoming SB ALF502L 72-203 R2. Note: For ALF 502R series engines, FAA AD 90-24-01 refers. FAA AD 90-24-01 supersedes FAA AD T89-13-52. Compliance: As detailed in requirement documents. Background: This Directive has been amended to include ALF502L series engines and to reflect a reduction in the inspection threshold. This amendment follows advice of cracking found in two discs at engine cycles below the 8,500 cycles since new inspection threshold detailed in FAA AD T89-13-52.