Cessna 182 N20847 accident near Baxterville, Mississippi

Probable cause

The failure of the No. 1 cylinder intake valve due to inadequate valve seating.

NTSB analysis

The pilot and passenger were conducting a personal flight when the engine experienced a partial loss of power. The pilot was unable to maintain altitude and made a forced landing to a road. During the forced landing, while turning right to stay on the road, the airplane ground looped and collided with trees, sustaining substantial damage.

Examination of the engine revealed that a portion of the No. 1 cylinder valve head was fractured due to the inward propagation of a radial rim fracture, and the initiation and propagation of a chordal fracture in the filet area perpendicular to the axis of the stem. The initial crack developed at the rim and propagated inward toward the center of the valve head as a radial rim crack. When the crack front reached the fillet region of the head, a second crack initiated and propagated in fatigue as a chordal fracture. A final overstress fracture occurred near the rim. This type of failure is likely due to cyclic uneven expansion and contraction stress cracks that propagate inward, as a result of inadequate valve seating.

The engine maintenance records showed that a repaired No. 1 cylinder was installed on May 9, 2014. The partial maintenance release stated that the cylinder repair process included refaced valves and three angle cut valve seats. There were no other entries related to the No. 1 cylinder. The engine had accumulated about 598 hours since the cylinder was installed. Annual inspections were completed every year after this cylinder installation.

Text from the NTSB. Open the NTSB docket for CEN20LA123 for the full record.