Cessna TU206 N150SC accident near Waikoloa Village, Hawaii

Probable cause

The total loss of engine power due to the failure of the No. 4 connecting rod crankshaft end and cap.

NTSB analysis

After flying for about 3 hours conducting aerial survey work, the pilot noticed a low oil pressure indication in the cockpit. The pilot prepared for a landing at the destination airport. During the approach he heard a bang and the airplane started to shake. He pitched the airplane to maintain the best glide speed and noticed the engine had lost all oil pressure. The pilot prepared for a forced landing to a road, during which the right wing struck a road sign, and the airplane came to rest in a ditch.

Examination of the engine revealed the No. 4 connecting rod crankshaft end and cap separated from the rod and the bolts were sheared. One of the nuts for the connecting rod cap bolts was split and both pieces were recovered. Signatures of high heat on the piston end of all the connecting rods was also noted.

The high heat signatures were consistent with a lack of oil lubrication (and subsequent cooling during operation) for the connecting rods at the crankshaft. The lack of lubrication likely caused the failure of the No. 4 connecting rod crankshaft end and cap, which resulted in a total loss of engine power. The reason for the lack of lubrication could not be determined from available information.

Text from the NTSB. Open the NTSB docket for WPR19LA185 for the full record.