Stuck exhaust valve leads to forced landing that injures two — General Aviation News

By General Aviation News Staff · August 9, 2024 · 11 Comments

The pilot reported that, during the initial climb after takeoff from Runway 20 at Nut Tree Airport (KVCB) in Vacaville, California, the Cessna 150H’s engine began to sputter while the airplane was about 200 to 250 feet above ground level.

The engine speed decreased to about 1,700 to 1,800 rpm.

The pilot verified that the mixture and throttle were in the takeoff positions, but the airplane was no longer climbing, and he had difficulty maintaining altitude.

As a result, he initiated a forced landing to an open field adjacent to the airport.

During the landing roll, the airplane hit uneven terrain and came to rest upright, resulting in substantial damage to the left wing and fuselage. The pilot and passenger sustained minor injuries in the crash.

Post-accident examination of the engine revealed that it was partially attached to the engine mount. The carburetor was separated from the intake spider.

The upper spark plugs and rocker box covers were removed and the propeller was rotated by hand. Rotational continuity was established throughout the engine. Thumb compression was obtained on cylinder Nos. 1, 3, and 4. No compression was obtained on cylinder No. 2, which was removed for further examination.

The No. 2 cylinder was intact and undamaged. The exhaust and intake valve springs were intact and oil coated, as were the intake and exhaust valve rocker arms.

The valve springs and keepers were removed. The intake valve slid out of the valve guide freely, but the exhaust valve slid out of the valve guide with a significant amount of force.

The exhaust valve stem exhibited carbon buildup along with the valve neck. White deposits were observed around the rim of the valve. The valve seat also exhibited carbon buildup.

The intake valve stem exhibited carbon deposits on the neck of the valve and stem. The valve seat contact area showed no carbon buildup, but a slight amount of carbon build-up was observed on the valve rim.

Probable Cause: The partial loss of engine power due to a stuck exhaust valve.

NTSB Identification: 105794

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This August 2022 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.