NTSB Factual Report

On July 25, 2010, at 1230 central daylight time, a Beech H35, N5443D, collided with terrain during a forced landing following a loss of engine power in Green Lake, Wisconsin. The pilot and passenger were not injured. The airplane sustained substantial damage to the engine firewall. The 14 Code of Federal Regulations Part 91 personal flight was operating in visual meteorological conditions without a flight plan. The last leg of the cross country flight originated at the Prairie Du Chien Municipal Airport (PDC), Prairie Du Chien, Wisconsin at 1145, with a destination of Wittman Regional Airport (OSH), Oshkosh, Wisconsin.

The pilot was en route to EAA AirVenture 2010 when the accident occurred. He reported that he descended to 1,800 feet and was slowing the airplane to 90 knots in preparation to approach OSH per the Notice to Airman when the engine lost power. The pilot selected an open field located next to a road in which to land. The pilot retracted the landing gear and landed the airplane uphill in a soybean field. The airplane slid 260 feet before coming to a stop. The airplane sustained firewall damage during the landing.

Post accident teardown inspection and disassembly of the Continental O-470-G-C1 engine revealed the oil pump screen was partially collapsed and it contained pieces metal particles. The oil sump contained metallic debris, which was consistent with bearing material. The torque on the cylinder deck studs and through bolts was measured using a calibrated torque wrench. All 12 of the cylinder through bolts were tight. Nineteen of the 36 cylinder deck studs were loose.

The cylinders, pistons, piston rings, valves, and camshaft were removed and found undamaged. The crankshaft exhibited thermal discoloring around the area of the number one connecting rod. The number one connecting rod bearing was mostly extruded from the connecting rod and it exhibited thermal damage and discoloration. Fretting was observed on the crankcase number two main bearing saddle. The number two main bearing saddle bearing tang was worn and smeared. The saddle surface area appeared to be smeared and shiny in color. A crack was observed between the number four main bearing saddle on the left half (even number cylinder half) of the crankcase. The crack extended through the number five main bearing saddle.

The number one, three, four, and five main bearings were intact and exhibited wear exposing the copper layer. The number two main bearing was separated into multiple portions.

The engine had received a top overhaul 18.72 hours prior to the accident.

NTSB Probable Cause

A total loss of engine power during descent due to the overhaul facility’s inadequate maintenance.