COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Cessna 170, 172, F172, FR172 and 175 Series Aeroplanes AD/CESSNA 170/62 Aeroquip Engine Exhaust Mufflers 7/98 DM Applicability: Cessna 172R aeroplanes as detailed by serial number in Cessna Single Engine Service Bulletin SB98-78-01. Requirement: In accordance with the procedures detailed in Cessna Single Engine Service Bulletin SB98-78-01: 1: Inspect the engine exhaust muffler, and if applicable: 2: de-activate the cabin heating system, and 3: install a placard, and 4: replace the engine exhaust muffler. Note: FAA Airworthiness Directive 98-02-05 refers. Compliance: Effective 6 May 1998: 1: Before further flight. 2: Before further flight. 3: Before further flight. 4: Within 50 hours time in service from the effective date of this directive. This airworthiness directive becomes effective on 6 May 1998. Background: This directive has been issued to require an inspection of the engine exhaust muffler, and if applicable, action to ensure a defective muffler does not result in carbon monoxide contamination of the aircraft heating system or the aircraft cabin. The requirement follows advice that certain mufflers produced by Aeroquip may have inadequate or failed welded joints.