The pilot reported that, after takeoff, the Zenith CH-750’s engine lost partial power about 100 feet above ground level and that he then attempted to return to the airport in Allentown, Pennsylvania.
He added that “the engine would not keep me flying and the airplane just fell into the forest.”
The pilot was seriously injured in the accident.
During the on-scene examination, the No. 1 spark plug was found missing from the cylinder head, but still attached to the ignition lead. The threads were stripped out of the cylinder head. It is likely that the No. 1 spark plug was liberated from the cylinder head due to the stripped threads, which led to the partial loss of engine power.
Probable cause: A partial loss of engine power due to the No. 1 spark plug being liberated from the cylinder head due to the stripped threads in the cylinder head. Contributing to the accident was the pilot’s decision to attempt to return to the airport while at a low altitude.
NTSB Identification: ERA15LA311
This August 2015 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.