COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Rolls Royce Turbine Engines - RB211 Series AD/RB211/12 N3 Governor with Approved Wear Resistance 9/90 Applicability: RB211-524G2-19, -524G2-19/11, -524G2-19/15, -524G3-19, -524G3-19/15. Engines prior to serial no 13118. Requirement: Action in accordance with Rolls Royce PLC Service Bulletin RB 211-73-8763 Rev 2. Compliance: Prior to 6 October 1990. Background: In the pump and governor the N3 governor is prone to excessive, premature wear, due to frettage. In extreme circumstances the governing function can be rendered inoperative. The changes introduced by this Service Bulletin have been shown to alleviate the wear problem.