On February 24, 2021, about 1600 central standard time, a Cessna 182F, N3209U, was substantially damaged when it was involved in an accident near Millville, Iowa. The commercial pilot and a passenger received minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot stated that, during a cruise climb from the departure airport, the engine made a “loud growling” noise and lost power. He turned the magnetos off when he saw smoke near the propeller and trimmed the airplane for a best glide airspeed. He said there was no suitable landing area in front of the airplane, but there was a road to the left of the airplane. During the approach to the road, he maneuvered the airplane below powerlines and avoided buildings before the airplane impacted the road and a snowbank. The airplane nosed over during the landing, resulting in substantial damage to the fuselage, right wing and right-wing strut.

Postaccident examination of the airplane revealed a hole in the engine crankcase located between the Nos. 2 and 5 cylinders. The No. 2 cylinder connecting rod was protruding through the hole and exhibited scoring consistent with oil starvation.

The vacuum pump did not exhibit any mechanical anomalies and the inside of its vacuum tube did not contain oil. There was a relatively large amount oil on the underside of the top engine cowling. There was no oil on the interior or exterior side of the bottom engine cowling. There was no oil on the engine firewall. There was oil on the underside of the fuselage extending aft of the engine crankcase breather tube to the empennage. There was oil around the crankcase nose seal consistent with a leak.

The inside of the crankcase breather tube, which alleviates normal crankcase pressure, was unobstructed and contained oil. The tube contained a whistle stop/vent located about three inches from the bottom of the tube, which was in accordance with its design. The oil breather tube whistle stop/hole was positioned aft and parallel to the airplane’s longitudinal axis. Examination of the breather tube showed dried and caked oil residue which were signs of progressive leakage. Similar signatures were observed at the crankcase nose seal. These would have been apparent during routine maintenance and/or a preflight inspection.

Continental Service Bulletin (SB) M89-9, Excessive Crankcase Pressures, provides a troubleshooting test when excessive crankcase pressures are suspected. The SB notes:

Excessive crankcase pressure in flight can be induced by ram air entering through an improper fitting oil cap seal and/or defective crankshaft nose seal. If the problem occurs on turbocharged engines only at higher altitudes, then it is possible that the turbocharger is suspect.