Cessna TU206

Full Narrative

On July 3, 2019, at 1035 Hawaii-Aleutian standard time, a Cessna TU206F, N150SC, was substantially damaged when it was involved in an accident near Waikoloa Village, Hawaii. The commercial pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 aerial observation flight.
The pilot reported that the flight was destined for Kona, Hawaii, to conduct aerial survey work. After flying for about 3 hours, he noticed a low oil pressure indication in the cockpit. The pilot prepared for a landing at Ellison Onizuka Kona International Airport (PHKO), Kona, Hawaii, during which 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 engine continued to run at an idle setting; however, the pilot had no throttle authority. He 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 by a Federal Aviation Administration inspector 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. The inspector also noted indications of high heat on the piston end of all the connecting rods with darkening on the crankshaft end of the No. 5 connecting rod.
There were numerous large pieces of the connecting rod cap and pistons that had migrated through the engine case resulting in further damage to several other cylinders and pistons. Cracks were observed on at least two other pistons and damage was noted to the cylinder mounting flanges on at least three cylinders.