During the airplane’s initial climb in crosswind conditions, the engine experienced a partial loss of power, and the airplane entered an aerodynamic stall.
The pilot attempted to lower the nose of the Globe GC1B, but with insufficient altitude, the plane hit a ditch parallel to the runway at the airport in Wellington, Florida, which resulted in substantial damage to the fuselage and both wings.
The pilot sustained serious injuries, while a passenger sustained minor injuries.
Examination of the airplane revealed that the engine’s No. 3 cylinder had low compression, and the No. 3 intake valve had hardened carbon deposit buildup on its stem.
After the valve was cleaned and reinstalled, the engine compression returned to the normal range.
It is likely that, during the initial climb, the intake valve stuck intermittently due to the carbon deposit buildup, which resulted in the partial loss of engine power and the airplane’s inability to climb.
Probable cause: The partial loss of engine power during the initial climb due to a sticking intake valve on the No. 3 cylinder.
NTSB Identification: ERA18TA222
This August 2018 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.
This is a strange one. How can an intake valve collect carbon on the stem ? It’s usually the exhaust valve stem that sticks.
The C125 is one of the early 6 cylinder Continentals from the 1940s to 1952.
One way to get ‘stuff’ on the intake valve is a large amount of oil getting ‘sucked’ into the intake past the guide, from the valve cover area.
The other possibility is a primer nozzle leaking onto the valve stem.
Yes strange indeed.
I would think any clearances in the valve guide would allow oil in from the rocker cover end of the head.
yes, aircraft engines are set up with fairly loose [ large ] clearances, being air cooled, so a small amount of oil is on both valve guides.
BTW, even more oil is left on the cylinder walls by the rings, which is why an aircraft engine burns some oil, from 10 hours per quart to 2 hours per quart [ the TCM limit ].
but this case is weird.!