Accident Overview
On July 20, 2022, about 1845 central daylight time, a Beech N35 airplane, registered as N1228Z, was substantially damaged during a forced landing in a field near Wardsville, Missouri. The pilot, who was the sole occupant, reported no injuries. The flight was conducted as a personal flight under Title 14 Code of Federal Regulations Part 91.
Events Leading to Forced Landing
The pilot stated that the departure, climb, and cruise phases were uneventful. During approach to the intended destination airport, the oil pressure gauge dropped to zero. Shortly thereafter, the engine began running rough, and the pilot heard a loud bang from the engine. Smoke was observed emanating from under the engine cowling. The engine then lost power completely, forcing the pilot to execute a landing in an open field. The impact damaged the forward fuselage.
Engine Examination Findings
Post-accident examination of the engine revealed catastrophic internal failures. The connecting rods, caps, and bolts for cylinders No. 1 and No. 4 had fractured at the crankshaft journal. The No. 5 connecting rod showed discoloration consistent with overheating due to oil starvation. A 3-inch by 3-inch hole was present in the upper crankcase above the No. 4 cylinder. Fragments of connecting rod caps and retaining bolts were recovered from the crankcase and oil sump, along with approximately one quart of oil.
During the examination, the aftermarket oil filter adapter was found to be loose; it could be rotated about 40 degrees with finger pressure. Safety wire was observed installed from the adapter spool to the oil pump housing, but without significant tension. No safety wire was found between the adapter sleeve and the engine.
Maintenance History and Regulatory Actions
The engine was overhauled in March 2021 and installed on the airframe on August 7, 2021, at an airframe time of 7,329 hours. The overhaul facility reported that the oil filter adapter was furnished already installed. Maintenance records show that on February 19, 2022 (7,379 hours), the oil filter adapter was removed and reinstalled with new copper gaskets due to an oil leak; the mechanic confirmed use of a torque wrench. On June 21, 2022 (7,405 hours), the pilot/owner changed the engine oil but did not replace the oil filter. At the accident time, airframe time was 7,420 hours.
The oil filter adapter manufacturer had issued updated installation instructions on February 21, 2020, specifying copper gaskets, torque to 65 ft-lbs, and safety wire from the adapter spool to the engine and from the adapter sleeve to the engine. A mandatory service bulletin (SB-001 Rev B) was revised on June 17, 2021, requiring inspection of the adapter installation at each oil change and 100-hour/annual inspection, with safety wire requirements reiterated.
FAA Airworthiness Directive (AD) 2022-04-04, effective March 29, 2022, mandated replacement of fiber gaskets with copper gaskets and reinstallation of the adapter within 50 flight hours or at the next oil change. At the accident, the adapter had copper gaskets installed. On June 16, 2022, the manufacturer issued SB-001 Rev C, specifying an improved lower gasket and an inspection within 10 flight hours or next annual/100-hour inspection.
Service bulletins are not regulatory for Part 91 operations; airworthiness directives are mandatory. The pilot/owner noted that alignment marks between the adapter and engine were still matched before the flight.