83-14-04: Cabin Heater Shroud Modification

83-14-04 CESSNA: Amendment 39-4684. Applies to all Model 172RG airplanes certificated in any category. Compliance: Required as indicated, unless already accomplished. To reduce the possibility of carbon monoxide contamination entering the cabin area, accomplish the following: a) Within the next 25 hours time-in-service after the effective date of this AD. 1) Modify the cabin heater shroud in accordance with Cessna Service Letter SE83-13 dated May 27, 1983. Additionally, prior to reinstallation of the cabin heater shroud, visually inspect the flanges on the outer diameter of the ends of the muffler for cracks and repair or replace any cracked components. 2) Within 50 hours time-in-service after the modification required by paragraph a)1) of this AD and each 50 hours time-in-service thereafter, visually inspect the shroud for security and proper location and the flanges on the outer diameter of the ends of the muffler for cracks and prior to further flight, repair or replace any cracked components. Removal of the shroud for this inspection is not required. 3) Reinspect any repaired component within 25 hours time-in-service after the repair and, if defective, repair or replace. If no defects are found, continue inspection of this component in accordance with paragraph a)2) of this AD. b) As an alternative to complying with paragraph a) of this AD, deactivate the cabin heat system by removing the cabin heat control cable from the control arm on the cabin heat valve 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 or safety wire the valve to the closed position. c) The airplane may be flown in accordance with FAR 21.197 to a location where this AD may be accomplished. This amendment supersedes AD 81-05-05 R1, Amendments 39-4075 and 39-4332. This Amendment 39-4684 becomes effective on July 20, 1983.