Cessna 120 N77068 accident near Jesup, Georgia

Probable cause

An oil starvation-induced catastrophic engine failure due to the improper installation of the crankshaft expansion plug during engine overhaul.

NTSB analysis

The pilot stated that they were about 1 hour and 20 minutes into their planned 2-hour cross country flight, when an opaque film began to accumulate on the airplane’s windshield. Engine oil was observed leaking from the forward right engine cowling area. Within a minute, forward visibility was severely restricted and the pilot had to rely on the instruments for level flight while referring out the side window for visual reference. There were no abnormal indications from the engine instrumentations. The nearest airport was too far away so the pilot elected to land in a clear field within gliding distance. The pilot approached the open field in a slip; the windshield was covered with oil. He lost visual reference as he recovered from the slip to land, and had to estimate the flare for the touchdown. The airplane landed hard and bounced, which separated the right wheel assembly from the gear. The airplane’s right gear dug in on the second contact with the ground, resulting in the airplane coming to an abrupt stop in a nose-low and tail-high position. A wreckage examination revealed the engine oil was leaking from the front section of the engine crankcase, behind the propeller flange. The forward crankshaft expansion plug was observed dislodged from it seating, allowing pressurized oil to escape from the forward end of the crankshaft. The airplane’s engine had been overhauled 39 flight hours prior to the accident.

Text from the NTSB. Open the NTSB docket for MIA08LA196 for the full record.