COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Skyfox Aviation (Hedaro) CA25 Series Aeroplanes AD/CA25/6 Gazelle Exhaust System 2/97 Applicability: CA25N Gazelle aircraft serial numbers up to and including CA25N042 not incorporating Helitech Engineering Order HEO-143. Requirement: To detect cracking of the exhaust system which may result in exhaust gas leakage and/or failure of the exhaust system, carry out an inspection of the exhaust system in accordance with the requirements of Skyfox Aviation Service Bulletin (SB) Number 14. Compliance: Effective 30 January 1997; unless previously accomplished, within 50 hours time in service and thereafter at intervals not to exceed 100 hours time in service. Background: This Directive has been issued to require inspection of the exhaust system. The requirement follows advice from the aircraft manufacturer of several incidents of cracking in the area where the exhaust manifold inlet tube enters the muffler chamber.