Beech B19 N774TA accident near Osage Beach, Missouri

Probable cause

The failure of the No. 4 piston wrist pin plug and the subsequent entry of its metal shavings into the oil system, which clogged the oil passages and caused the engine to seize. Contributing to the accident was the installation of engine parts that were not approved by the engine manufacturer.

NTSB analysis

The pilot reported that, shortly after takeoff, he noticed that the oil pressure was dropping. Shortly after the oil pressure dropped, the engine seized, and the pilot subsequently ditched the airplane in a lake.

When the airplane was recovered, the oil dipstick was missing. However, more than 4 quarts of oil and only about 1 to 2 cups of water were drained from the engine. If the dipstick had not been in the engine at impact, the engine would have been full of water. Further, the pilot reported that he had replaced the dipstick after checking the oil; so, the dipstick likely was in place at impact. No signs of oil were found in the engine cowling, and no oil streaks were observed underneath the fuselage. A postaccident examination of the engine revealed that the crankshaft middle bearing had seized. The third bearing aft, which was between the two banks of cylinders, and the No. 3 connecting rod bearing had rotated and exhibited severe heat distress and mechanical damage. The No. 4 piston wrist pin plug was deformed, and the deformation had damaged the side of the piston. Aluminum pieces and shavings were found throughout the engine. It is likely that, as the No. 4 wrist pin plug wore down, its shavings entered the oil system and clogged the oil passages, which caused the engine to seize. The examination also revealed that the engine parts installed on the airplane, including the No. 4 piston wrist pin plug, were not approved by the engine manufacturer.

Text from the NTSB. Open the NTSB docket for CEN15LA172 for the full record.