COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Teledyne Continental Motors Piston Engines AD/CON/75 Magneto Timing 10/96 Applicability: Teledyne Continental Motors (TCM) O-200A, O-200B and Rolls Royce O-200A, O- 200B and O-200C engines. Requirement: To prevent possible cylinder cracking with a subsequent loss of engine power. 1. (a) For engines fitted with one or more cylinders with a part number lower than 641917, set the engine magneto timing to 24 degrees (plus or minus 1 degree) before top dead centre (BTDC) on both magnetos in accordance with the procedures detailed in TCM Service Bulletin (SB) No. SB94-8, and 1. (b) Stamp the engine data plate to reflect a magneto timing of 24 degrees BTDC. 2. (a) For engines fitted with all four cylinders part number 641917 or higher, the engine magneto timing may be set to 28 degrees (plus or minus 1 degree) BTDC on both magnetos in accordance with the procedures detailed in TCM SB No. SB94-8, and 2. (b) Stamp the engine data plate to reflect a magneto timing of 28 degrees BTDC. Note: FAA Airworthiness Directive 96-12-06 refers. Compliance: Requirement 1. Unless previously accomplished, within 50 hours time in service after 12 September 1996 and thereafter at each cylinder replacement. Requirement 2. Effective 12 September 1996 and thereafter at each cylinder replacement. Background: This directive has been issued to require the engine magneto timing to be set in consideration of the status of the cylinders fitted. The requirement addresses reports of cylinder cracking in engines fitted with early model cylinders.