COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Allison Turbine Engines - 250 Series AD/AL 250/54 Amdt 1 Engine Turbine Assembly No. 8 Bearing U-Ring Installation 5/84 Applicability: Allison 250-C28B/C28C engines. Document: Allison 250 C28B/C28C CEB-A-72-2082 Rev 1. Note: FAA AD Allison 83-01-04 AMDT. 39-4539 refers. Compliance: In accordance with the Requirement Documents. Background: This have been instances of an air leak occurring into the No. 8 bearing sump, forcing oil through the No. 8 bearing labyrinth seal onto the No. 1 turbine wheel, resulting in oil fires and damage to first stage turbine wheels. This Directive is raised in issue to ensure compliance with Revision 1 of the document which is a complete revision replacing the original.