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Exhaust leak prompts ADExhaust leak prompts AD

Concern about potential carbon monoxide poisoning that could result from reported exhaust leaks involving the Lycoming TIO-540-AJ1A engine has prompted an airworthiness directive (AD) requiring initial and recurring inspections affecting 758 engines currently in service.

The FAA has issued an airworthiness concern sheet for Lycoming’s TIO-540-AJ1A engine that could have possible exhaust leaks that could allow carbon monoxide gas to enter the cockpit.

The AD was published June 13 and takes effect June 28; required exhaust system inspections are estimated to cost $85 each, or an estimated $64,430 to inspect exhaust assemblies across all TIO-540-AJ1A engines in service.

AOPA has worked with the FAA since the potentially unsafe condition came to light to notify affected aircraft owners. The reported exhaust leaks prompted the first airworthiness concern sheet ever issued by the FAA Engine and Propeller Directorate. The problem has been attributed to cracked welds and exhaust studs pulling the exhaust assembly away from a cylinder.

Lycoming issued a mandatory service bulletin Aug. 31 requiring exhaust system inspection within 10 hours of the bulletin’s release and every 25 flight hours thereafter for engines with less than 1,000 hours, and every 50 flight hours following initial inspection for engines with more than 1,000 hours. The service bulletin allowed longer inspection intervals for aircraft with an installed carbon monoxide detector, though the AD published June 13 does not make that distinction.

The FAA considers the AD an interim step while Lycoming works to determine the root cause, and may take further action once that is known, the agency noted in the document.

Jim Moore

Jim Moore

Editor-Web
Editor-Web Jim Moore joined AOPA in 2011 and is an instrument-rated private pilot who enjoys competition aerobatics.
Topics: Aircraft Maintenance, Ownership, Airworthiness Directives

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