What happened
A pilot and two passengers were performing an aerial timber survey when the aircraft's engine began backfiring, running rough, and losing power while in cruise flight at approximately 1,000 feet. Following the loss of power, the engine stopped functioning entirely.
The pilot attempted an emergency landing on a gravel bar located along a glacial-fed river. During the approach, the aircraft landed short of the chosen site, making contact with approximately three feet of water, which caused the plane to nose over.
The investigation
An FAA airworthiness inspector examined the aircraft following its recovery. The inspection revealed that the number seven cylinder was cracked and the number nine cylinder showed no compression. Additionally, approximately one cup of clear water was discovered inside the carburetor float bowl.
The inspector could not confirm whether the damage to the cylinders or the presence of water in the carburetor resulted from the impact with the river water. Upon further disassembly of the engine, the number nine cylinder head was found to have separated from the cylinder barrel.