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 170/48 Exhaust Muffler/Shroud 9/83
Applicability: Model 172RG with S/Nos 172RG0001 to 172RG1134.
Requirement: 1. Modify the muffler shroud in accordance with Cessna SL No SE83-13. In addition, visually inspect the flanges on the outer diameter of the ends of the muffler for cracks prior to reinstallation of the muffler shroud. Repair or replace any cracked components.
2. Visually inspect the muffler shroud for security and proper location and the flanges on the outer diameter of the ends of the muffler for cracks. Repair or replace any cracked components before further flight. Removal of the muffler shroud for this inspection is not required.
3. Reinspect any repaired components.
Note: As an alternative to comply with paragraphs 1, 2 and 3 of the requirement, deactivate the cabin heat system by removing the cabin heat control cable from the control arm on the cabin heat located on the firewall at the right upper side of the engine compartment. Ensure that the valve spring mechanism is functioning and that the cabin heat valve is spring loaded to the closed position and wire locked in the closed position. FAA AD 83-14-04 Amdt 39-4684 refers.
Compliance: Para 1 - Within 25 hours time in service after 31 August 1983.
Para 2 - Within 50 hours time in service after the modification detailed in para 1 of the requirement has been embodied and repeated thereafter at intervals of 50 hours time in service.
Para 3 - Within 25 hours time in service after the repair.
Background: An overseas Authority and the manufacturer, require modification and repeated inspections to the exhaust muffler/shroud assembly in order to prevent the possibility of carbon monoxide contamination. This action supersedes that taken in cancelled AD/CESSNA 170/41.