Amateur-built EXPLORER N6663K accident near East Bend, North Carolina

Probable cause

A total loss of engine power likely due to a failure of a rotary valve shaft seal and the pilot’s failure to detect and diagnose the impending failure during the preflight inspection.

NTSB analysis

The accident pilot/owner purchased the experimental amateur-built airplane about 1 year before the accident, and, according to the airplane's previous owner, it had not been flown in the 4 years preceding the sale. The airplane's maintenance records had been lost and were not provided to the new owner during the sale. The pilot reported that, although he had performed some basic maintenance on the airframe and engine about 3 months before the accident flight, the airplane had not undergone the required annual condition inspection before the flight.

On the day of the accident flight, the pilot "topped off" the engine's rotary valve oil tank before conducting several local passenger-carrying flights; the pilot held a student pilot certificate and did not have an endorsement to fly the accident airplane make and model solo nor was he authorized to carry passengers in any aircraft. During the accident flight, while maneuvering at an altitude of about 450 ft above the ground, the engine suddenly lost all power. During the subsequent landing attempt, as the pilot was trying to avoid striking a power line, the airplane entered an aerodynamic stall and impacted the ground, which resulted in substantial damage to the airframe and serious injury to the pilot.

Postaccident examination of the engine revealed that one of the rotary valve shaft seals was destroyed and that substantial oil deposits were present inside the air intake, on the pistons and spark plugs, and on components in the engine's exhaust path. The rotary valve oil tank was also completely absent of oil. Although the exact reason for the loss of engine power could not be determined, the failure of the rotary valve shaft seal likely contributed to its failure. The excessive rotary valve oil consumption was an indication that a rotary valve shaft seal had failed. The pilot should have recognized this problem when he topped off the rotary valve tank before the accident flight and attempted to diagnose it before taking off.

Text from the NTSB. Open the NTSB docket for ERA14LA338 for the full record.