FAA AC 43-16A Alert Number 339 October 2006 - Carbon Monoxide Poisoning Potential

by FAA AFS-600 Regulatory Support Division


(All: Powered Models); Carbon Monoxide Poisoning Potential: ATA 7800

(The following safety admonition has been contributed by Aerospace Engineer Barry Ballenger from the Kansas City office of Continued Operational Safety. Contact information is found at the article's end.)

"With the onset of cold weather, maintenance personnel should take extra time to inspect the exhaust system components when performing engine maintenance. Many small airplanes use exhaust system heat for cabin heat and defrosting windshields. Typically, a heat exchanger or muff is used to collect the heat off the exhaust system and pipe it to the cabin through flexible ducting. If the exhaust system has leaks, improper connections, or damage, carbon monoxide from engine combustion may enter into the heat/defrost systems and into the cabin. Carbon monoxide may also enter through the firewall due to improperly installed or deteriorated seals. Other entry points for carbon monoxide include wheel well areas, windows, and fresh air vents.

"Technicians should inspect all exhaust system components for condition with particular attention to areas associated with cabin heat and defrost systems. Look for deformation, corrosion, erosion, cracks, burned spots, and loose or missing hardware. Heat muffs should be removed to inspect the condition of the exhaust system hidden by their installation. Inspect for signs of exhaust leakage such as powdery deposits or stains. Replace any defective parts. Inspect for any non-approved repairs to exhaust components. Many exhaust system components are not field repairable. Signs of any exhaust system repair without proper documentation are cause for rejection. Inspect the firewall for condition and security of all pass-through locations such as electrical or plumbing, engine controls, and steering controls. Ensure the pass-through sealant or seals are in serviceable condition and will not allow exhaust gases into the cabin area. Door and window seals should be checked for condition and security.

"Certification regulations limit the level of carbon monoxide to 1 in 20,000 parts (0.005%) of air in the passenger compartment. Reasonably priced carbon monoxide detectors are available for technicians to measure carbon monoxide levels. Measuring the carbon monoxide level is the best method to ensure dangerous exhaust gases are not entering the passenger area.

"It is the maintenance technician's responsibility to ensure the airworthiness of any engine installation. Remember, part of being airworthy means the aircraft is safe for flight. By spending a little extra time during engine maintenance, the technician can ensure the safety of the aircraft's exhaust system."...

Click here to read the full FAA Advisory Circular, AC 43-16A Alert Number 339 October 2006 - Carbon Monoxide Poisoning Potential.

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