NTSB Issues Urgent Safety Alert on Piston-Engine Exhaust Valves
The National Transportation Safety Board (NTSB) has issued a critical safety alert urging general aviation pilots, aircraft owners, and maintenance personnel to pay close attention to exhaust valve condition in piston aircraft engines.
The numbers behind the warning are sobering. In safety alert SA-109, investigators examined 42 accidents between 2015 and 2025 in which a stuck or sticking exhaust valve led to engine power loss. These accidents resulted in five fatalities and 12 serious injuries.
Sticking valves disrupt the combustion cycle in reciprocating piston engines, causing severe vibration and partial—or sometimes total—power loss. These problems can occur during critical phases of flight, including takeoff and landing.
The FAA identifies deposits of lead, carbon, and varnish on valve stems and guides as primary causes. Risk may be increased by:
- Infrequent flying
- Localized overheating
- Sudden engine cooling
Piston-powered helicopters and flight school aircraft are identified as especially vulnerable because of their higher operating temperatures, rich mixture settings, and repetitive pattern-work flying.
The NTSB urges pilots to recognize the warning signs before takeoff. Addressing a sticking valve on the ground is far safer than dealing with one in the air. The full safety alert is available on the NTSB’s official website.
Source: AVweb – NTSB Warns of Sticking Exhaust Valves in Piston Aircraft Engines