Accident Details
On October 5, 2018, at about 1445 central daylight time, a North American Navion A, registration N969TR, was substantially damaged during a forced landing near Stonewall, Mississippi. The private pilot, who was also the registered owner, was not injured. The flight was operated as a personal flight under Title 14 Code of Federal Regulations Part 91.
The flight departed Key Field Airport (MEI) in Meridian, Mississippi, at 1438, destined for Jack Edwards National Airport (JKA) in Gulf Shores, Alabama. Visual meteorological conditions prevailed, and no flight plan was filed.
According to the pilot, while cruising at 3,500 ft, the engine began to sputter. He informed air traffic control of his intention to return to MEI and turned back toward the airport, but the engine then stopped producing power. Realizing he could not reach MEI or any other airport, the pilot executed a forced landing onto a highway. He reduced airspeed to avoid hitting cars and touched down hard. The landing gear collapsed, and the airplane slid about 200 ft before coming to rest upright on the road. The impact resulted in substantial damage to the fuselage.
Engine Examination
A postaccident examination of the engine revealed that the No. 3 cylinder exhaust valve had fractured where the stem transitioned to the valve head. The valve head was found lodged between the crankcase and the camshaft, and the camshaft was fractured between the No. 3 intake and exhaust lobes.
Metallurgical examination of the liberated valve head and valve stem showed that the valve head was damaged from repeated contact with the piston. The valve stem exhibited fracture surfaces consistent with fatigue. The fatigue cracking had propagated through the valve stem, initiating at multiple sites on the stem surface. The valve stem also showed tapering near the fracture surface, along with surface oxidation and deposits of lead-based compounds on the exterior adjacent to the fracture. A small depressed area on the top face of the valve stem was consistent with repeated contact with the adjacent rocker.
Maintenance History
The last annual inspection of the airplane and engine was performed on August 1, 2018. At the time of the accident, the engine had accumulated a total of 1,705.0 hours, with 641.5 hours since overhaul. Review of the engine maintenance logbook revealed that on May 4, 2014, at an engine total time of 1,390.4 hours and 322.1 hours since overhaul, a mechanic had removed and reinstalled all six cylinders with new base seals, push rod tube seals, intake tube seals, exhaust gaskets, and rocker gaskets after resurfacing valves and seats.