AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 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. Rotax Piston Engines AD/ROTAX/18 Replacement of Valve Spring Retainers of Engines in Single Valve Spring Configuration 12/2003 Applicability: Rotax 912 A series engines with Serial Number (S/N) 4,410.204 up to and including 4,410.421. Rotax 912 F series engines with S/N 4,412.757 up to and including 4,412.807, but excluding 4,412.795. Rotax 912 S series engines with S/N 4,922.501 up to and including 4,922.636, but excluding 4,922.535, 4,922.553 and 4,922.578. Rotax 914 F series engines with S/N 4,420.039 up to and including 4,420.253, but excluding 4,420.049, 4,420.068, 4,420.083, 4,420.098, 4,420.115 and 4,420.156. In addition to the above, all engines that have been converted to a single valve spring configuration at engine repair/overhaul in accordance with Rotax Service Instruction (SI) SI-14-1997. Requirement: Unless previously accomplished, replace valve spring retainers with new improved valve retainers in accordance with instructions contained in Rotax Service Bulletin (SB) 912-022 and Rotax SB-914-011. Note: Austrian CAA AD 108 refers. Compliance: a. New Engines: Before next flight after the effective date of this Directive. b. Engines with not more than 10 hours time-in-service (TIS): Prior to the accumulation of 10 hours TIS. c. Engines with more than 10 hours TIS but less than 25 hours TIS: Prior to the accumulation of 25 hours TIS. d. Engines which have had the oil system opened during repair/maintenance: Within the next 10 hours TIS. e. Engines with more than 25 hours TIS (except those affected by (d)): At the next 100 hour inspection after the effective date of this Directive. Rotax Piston Engines AD/ROTAX/18 (continued) This Airworthiness Directive becomes effective on 27 November 2003. Background: Due to a delay in the purging of the lubrication system during starting, it is possible that the valve spring retainers may crack due to a number of reasons outlined in the SB's relevant to this Directive. The Austrian CAA requires replacement of the retainers with new reinforced retainers. Jim Coyne Delegate of the Civil Aviation Safety Authority 14 October 2003 The above AD is notified in the Commonwealth of Australia Gazette on 5 November 2003.