N1228ZBeech N35 · 1961

On July 20, 2022, about 1845 central daylight time, a Beech N35 airplane, N1228Z, was substantially damaged when it was involved in an accident near Wardsville, Missouri. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 personal flight.

The pilot reported that the departure, climb, and cruise portions of the flight were without incident. During the approach into the intended destination airport, he observed the oil pressure drop to zero and, shortly afterward, the engine started running rough. The pilot subsequently heard a “bang” from the engine and observed smoke from under the engine cowling. The engine lost power completely and he executed a forced landing to a field. The airframe sustained damage to the forward fuselage.

An engine examination revealed that the Nos. 1 and 4 cylinder connecting rods, connecting rod caps, and bolts had failed at the crankshaft journal. In addition, the No. 5 connecting rod was discolored at the crankshaft consistent with overheating due to oil starvation. The upper portion of the crankcase above the No. 4 cylinder exhibited a 3 inch by 3 inch hole. Connecting rod cap and retaining bolt fragments were recovered from the crankcase and oil sump, along with about one quart of oil. At the time of the examination, the aftermarket oil filter adapter was loose and could be rotated about 40° using only finger-tip pressure. One safety wire was installed directly from the adapter spool to the oil pump housing and without any significant tension. There was no safety wire installed between the adapter sleeve and the engine.

According to the airplane’s maintenance records, the engine was overhauled in March 2021 and installed on August 7, 2021, at an airframe time of 7,329 hours. A representative of the overhaul facility reported the oil filter adapter was furnished installed with the overhauled engine. The maintenance records noted that, on February 19, 2022, at 7,379 hours airframe time, the oil filter adapter was removed and reinstalled using new copper gaskets due to an oil leak. The mechanic confirmed that a torque wrench was used when reinstalling the adapter. On June 21, 2022, at 7,405 hours airframe time, the engine oil was replaced by the pilot/owner. According to the pilot/owner, the oil filter was not replaced at that time. In addition, he stated the alignment marks between the adapter and the engine were still matched up. At the time of the accident, the airframe time was 7,420 hours.

On February 21, 2020, the oil filter adapter manufacturer issued updated installation instructions (DN ST002 Rev 1) that implemented the use of copper gaskets, replacing the original fiber gaskets. The instructions required the use of a torque wrench to 65-ft lbs and installation of safety wire from the adapter spool to the engine, and from the adapter sleeve to the engine.

On June 17, 2021, the oil filter adapter manufacturer revised a previously issued mandatory service bulletin (SB-001 Rev B) regarding the oil filter adapter installation. The bulletin specified removal of any fiber gaskets still in service and the use of copper gaskets due to reports of oil leaks. The adapter installation was to be inspected for security and proper safety wire installation at each oil change, each 100-hour/annual inspection, and any time the adapter was removed or installed. The bulletin reiterated that safety wire be installed from the adapter spool to the engine, and from the adapter sleeve to the engine.

FAA Airworthiness Directive (AD) 2022-04-04 became effective on March 29, 2022. The AD mandated replacement of the fiber gaskets with copper gaskets and the reinstallation of the adapter, as noted in the corresponding service bulletin, within 50 flight hours or at the next oil change, whichever occurred first. The oil filter adapter was equipped with copper gaskets at the time of the accident.

On June 16, 2022, the adapter manufacturer revised the service bulletin (SB-001 Rev C) to specify an improved gasket to be used in place of the lower copper gasket. It also specified an inspection of the adapter installation within 10 flight hours or at the next annual/100-hour inspection, whichever occurred first.

Service bulletins are not regulatory in nature and compliance is not required for aircraft operated under 14 CFR Part 91. Airworthiness directives are regulatory in nature and compliance is required as specified in the directive.