Accident Overview
On March 12, 2022, at approximately 1245 central standard time, a Beech A36, registration N9410Q, was substantially damaged in an accident near Heavener, Oklahoma. The pilot and two passengers were not injured. The airplane was operated as a personal flight under Title 14 Code of Federal Regulations Part 91.
Pilot Actions
The flight originated from Bentonville Municipal Airport/Louise M Thaden Field (VBT), Bentonville, Arkansas, with a destination of Mena Intermountain Municipal Airport (MEZ), Mena, Arkansas. During descent into the destination, the pilot observed a dramatic drop in oil pressure to 14 psi. He began searching for alternate airports due to the unreachable destination and mountainous terrain. Turning westward toward Robert S. Kerr Airport (KRKR), Poteau, Oklahoma, the oil pressure dropped to zero within 1-2 minutes, and the engine seized. The pilot executed a forced landing to a field. During landing, the airplane struck fences and livestock feeding troughs, resulting in substantial damage to the wings.
Postaccident Examination
Examination after the accident revealed that the engine No. 4 cylinder rocker cover was completely off, and the No. 6 cylinder rocker cover was secured by only 4 bolts, all very loose. The No. 4 cylinder rocker cover gasket was not located after the accident. The No. 4 cylinder rocker arm shaft bolt was missing. Multiple rocker cover bolt holes were elongated and embossed with the bolt thread pattern. Metal shavings were observed throughout the valve assembly area and deposited on the cowling and airplane, along with lost engine oil.
Maintenance History
Review of maintenance records showed that the most recent engine maintenance was an oil change performed on December 22, 2021. The entry noted a post-maintenance engine run with no leaks and no mention of work on rocker covers. An annual/100-hour inspection was performed on November 17, 2021, with a normal post-maintenance engine run; no specific notation regarding leaks or rocker cover work was recorded. The engine had been overhauled and reinstalled on November 2, 2016. Subsequent maintenance entries since the overhaul did not mention any work on rocker covers. Interviews with personnel at the maintenance facility that performed the overhaul confirmed that approved hardware and gaskets were used. The mechanic who performed the oil change stated he did not access the rocker covers and had no reason to. Further attempts to determine when the rocker covers were last removed were unsuccessful.