Accident Details
On February 24, 2021, at about 1600 central standard time, a Cessna 182F, registration N3209U, was substantially damaged when it collided with terrain during a forced landing near Millville, Iowa. The commercial pilot and a passenger received minor injuries. The flight was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
Pilot Actions
According to the pilot, during a cruise climb from the departure airport, the engine emitted a “loud growling” noise and lost power. The pilot turned the magnetos off after observing smoke near the propeller and trimmed the airplane for best glide airspeed. He reported no suitable landing area ahead but identified a road to the left. During the approach, he maneuvered the airplane below powerlines and avoided buildings before impacting 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
Examination of the engine revealed a hole in the crankcase between the No. 2 and No. 5 cylinders. The No. 2 cylinder connecting rod protruded through the hole and exhibited scoring consistent with oil starvation. The vacuum pump showed no mechanical anomalies, and its tube contained no oil. A relatively large amount of oil was found on the underside of the top engine cowling, but no oil was present on the interior or exterior of the bottom cowling or on the engine firewall. Oil was observed on the underside of the fuselage extending aft from the crankcase breather tube to the empennage, and around the crankcase nose seal, consistent with a leak.
Additional Findings
The crankcase breather tube, which alleviates normal crankcase pressure, was unobstructed and contained oil. The tube included a whistle stop/vent located about three inches from the bottom, in accordance with its design. The 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, indicating progressive leakage. Similar signs were observed at the crankcase nose seal. These would have been apparent during routine maintenance or a preflight inspection.
Continental Service Bulletin (SB) M89-9, titled “Excessive Crankcase Pressures,” provides a troubleshooting test for suspected excessive crankcase pressures. The SB notes that in-flight excessive crankcase pressure can be induced by ram air entering through an improper-fitting oil cap seal or defective crankshaft nose seal, and that turbocharged engines at higher altitudes may indicate a turbocharger issue.