Cessna U206B N3830G accident near Winterset, Iowa

Probable cause

The loss of oil pressure to the No. 4 connecting rod journal and the subsequent loss of engine power.

NTSB analysis

The pilot stated that he departed the airport with six parachutists for a jump flight. As the airplane approached 1,000 feet above ground level, he noticed that the airplane wasn’t climbing. He checked the engine gauges and noticed that the engine analyzer was flashing “CHT” and the cylinder head temperature was 454 degrees F. As the pilot pitched the nose down and turned back to the airport, he heard a muffled “thud” sound and saw white smoke pour from the engine. As he prepared for a forced landing, four of the parachutists jumped from the airplane. The pilot then performed a forced landing in a field, coming to a stop near a dirt berm. An examination revealed a hole in the engine crankcase, near the No. 4 cylinder. Various pieces of metal, including part of a “quick oil drain plug” were found in the engine oil sump. The No. 4 connecting rod journal appeared distorted and displayed extensive heat signatures. The crankshaft journals on either side of the No. 4 rod journals did not appear to be distorted or to contain the same heat signatures and were coated with engine oil. The rod and crankshaft bearings were scored. The signatures on the engine were consistent with the loss of lubricant to the No. 4 connecting rod journal. A reason for the loss of engine oil to the journal was not found.

Text from the NTSB. Open the NTSB docket for CEN12LA224 for the full record.