Sticking Exhaust Valves Trigger NTSB Safety Alert
Owners and operators of piston-engine aircraft should have a licensed mechanic check valve condition and deposit buildup at the next inspection.
Updated on Nov. 4, 2026 in Auto Parts
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The National Transportation Safety Board issued safety alert SA-109 on October 29, 2026, warning pilots and owners about sticking exhaust valves in piston-powered aircraft engines. The alert follows 42 accidents investigated between 2015 and 2025 in which a stuck valve contributed to a loss of engine power.
Why it matters
Those accidents caused five fatalities and 12 serious injuries, which is why the NTSB is drawing attention to a component that can fail quietly. For owners of piston-engine aircraft and flight-school fleets, a stuck valve is a maintenance and safety issue rather than a routine repair, and the alert puts the warning signs in front of them now.
The NTSB investigated 42 accidents from 2015 to 2025 in which a stuck valve contributed to a loss of engine power, resulting in five fatalities and 12 serious injuries. Piston-powered helicopters and flight-school aircraft may be particularly susceptible to sticking valves.
The players
National Transportation Safety Board (NTSB)
The federal agency that investigates transportation accidents and issues safety alerts, including those on aircraft engine components that affect general aviation owners and operators.
The details
Sticking valves disrupt the combustion cycle in reciprocating piston engines. Deposits that accumulate on the valve stem or inside the valve guide are the primary cause, and localized overheating, infrequent flying, rapid engine cooling, incorrect fuel-air mixture settings, high ambient temperatures, low-airspeed operations and high-lead fuel can all contribute to buildup. A stuck valve can bend pushrods depending on where it sticks in its guide, and it can produce severe vibration and partial power loss, often showing up as a rough-running engine during cold starts.
Timeline
2015 to 2025: the NTSB investigated the 42 stuck-valve accidents.
October 29, 2026: the NTSB issued safety alert SA-109 on sticking valves.
The Home Front
The NTSB's safety alert process is the mechanism it uses to flag recurring component failures across the aviation fleet. SA-109 applies that process to sticking exhaust valves, a maintenance issue that sits alongside the routine engine upkeep that owners of piston aircraft already budget for.
If you own or fly a piston-engine aircraft, ask your mechanic to check valve condition and deposit buildup during your next scheduled inspection, and note any rough running, especially on cold starts. Maintenance on the engine itself should be handled by a licensed aircraft mechanic rather than done as a do-it-yourself job.
The takeaway
A rough-running piston engine on cold starts can signal a stuck valve, so flag it to a licensed mechanic instead of waiting for the next inspection. Keep a written record of engine maintenance and fuel type so a mechanic can check the likely causes of deposit buildup.
Further reading
For more on the parts and components that keep vehicles running safely, see Auto Parts.
Source note: This article includes information reported by AVweb.
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