COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Aerospatiale (Socata) TB20 (Trinidad) Series Aeroplanes AD/TB20/27 Amdt 2 Exhaust System Clap Locknuts 5/97 Applicability: All TB20 aircraft not incorporating HSJ Aviation (HSJ) Engineering Order HSJ 1330 or HSJ Drawing 5202, and HSJ Engineering Order HSJ 1486. Requirement: To prevent failure of the exhaust system; inspect, modify and assemble the exhaust system in accordance with the requirements of Socata Service Bulletin No. SB 10-072-78 Amendment 2. Note: DGAC Airworthiness Directive 92-152(A)R4 refers. Compliance: Unless previously accomplished in accordance with Amendment 1 of this Directive; within 50 hours time in service after 24 April 1997, and thereafter at each disassembly of the exhaust system. This Amendment becomes effective on 24 April 1997. Background: This Directive was originally issued to address concern for the integrity of the TB20 exhaust system following two TB10 in-flight exhaust system separation events in Australia. Amendment 1 of the Directive reflected the manufacturer's revision to the part numbers of the replacement exhaust pipe and the long manifold to exhaust pipe clamps. This amendment reflects the manufacturer's second revision of the requirement document. The revision, in part, introduces a new exhaust pipe to engine cylinder seal part number and revises the exhaust assembly torque data. Amendment 1 of this Airworthiness Directive became effective on 28 March 1996. The original issue of this Airworthiness Directive became effective on 26 May 1994.