NTSB Factual Report

On July 5, 2014, about 1900 eastern daylight time, an experimental amateur-built Explorer, N6663K, was substantially damaged during a forced landing near East Bend, North Carolina. The student pilot/owner was seriously injured and the passenger was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight, which originated from a private airstrip in East Bend, North Carolina. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91.

On the morning of the accident flight, the student pilot washed the airplane and serviced the fuel tank with 9 gallons of automotive fuel. Later that evening, the pilot performed a preflight inspection of the airplane and a runup check of the engine and noted no anomalies. He then departed on a brief local flight and returned to the departure airport. Upon returning, he performed four subsequent local flights, each with one passenger aboard. After boarding for the fifth and final passenger flight, the pilot taxied the airplane to the end of the runway where he performed another uneventful runup check of the engine.

The pilot stated that after takeoff, he climbed the airplane to about 400 feet, then "made a button hook" near the west end of the runway, and flew back across the runway at an altitude of about 450 feet. After flying past the east end of the runway, the pilot flew away from the airport with the intention of entering the downwind leg of the traffic pattern. About that time, the engine suddenly lost all power. The pilot further described that the power loss was sudden in nature, similar to shutting off the magnetos, and was not preceded by sputtering, roughness, or a loss of engine rpm. He subsequently decreased the airplane's pitch attitude, slowed to 60 mph, and identified a field for a forced landing.

During the turn from the base to the final leg of the approach, the pilot attempted to restart the engine to no avail. The final approach to the field placed the sun directly facing the pilot, and while on short final approach the pilot saw a "flicker" that he realized was a power line. The pilot stated, "I immediately used what airspeed I had to climb over the power lines. At this point all I could do [was] fly the plane the best I could until I impacted the ground." The pilot could not recall the events that transpired between that point and when he was extricated from the airplane by first responders.

A witness, who was a volunteer firefighter, and his family were driving in their car when they saw the accident airplane flying overhead. Upon reaching their home, the witness's wife observed the airplane as it descended and impacted the ground. The witness did not observe the impact, but could hear the airplane in the moments leading up to it. He stated that the engine sounded like it was "sputtering" before it lost power completely and then impacted the ground.

The witness and his father, who was also a firefighter, responded to the scene immediately. They attempted to assess the hazards at the scene and noted that there was no spillage or smell of fuel, and that when they knocked on the exterior of the fuel tank, it sounded "hollow." The witness also began to triage the pilot in preparation for emergency responders, who were enroute. When asked to discuss the circumstances surrounding the accident, the pilot told the witness that the airplane had "run out of gas" and then the engine lost power. The pilot had intended to perform a forced landing to the farm field where the airplane ultimately crashed, but while on final approach to the field the pilot observed an overhead utility line. At the last moment, the pilot increased the airplane's pitch in an attempt to avoid the line. The airplane then entered an aerodynamic stall and impacted the ground about 50 feet beyond the utility line.

A Federal Aviation Administration inspector examined the airplane at the accident site. According to the inspector, the steel tube structure of the airplane was fractured in several places. She observed no evidence of fuel leakage and found the fuel tank cap was properly secured. The fuel tank contained a quantity of fuel that the inspector estimated to be less than one gallon.

During a follow-up interview conducted several weeks after the accident, the pilot stated that he had originally attributed the loss of engine power to fuel exhaustion. He then discovered that when the airplane was being recovered from the accident site, about 4.5 gallons of fuel were drained from the fuel tank.

The pilot held a student pilot certificate, which was issued in December 2011. The limitations section of the certificate stated, "passenger carrying is prohibited." The certificate was endorsed by a flight instructor in December 2011 for the pilot to conduct solo flights in an experimental amateur-built Stolp SA-500. He reported that he had accumulated 450 total hours of flight experience, 173 hours of which were in the accident airplane make and model. His most recent third class medical certificate was issued in May 2006.

According to FAA records, the experimental amateur-built airplane was manufactured in 1992. It was equipped with a Rotax 582UL DCDI, two-stroke engine, with a rated power output of 65 horsepower. The engine was equipped with a rotary valve oil tank, which was present to provide lubrication to the rotary valve shaft. The closed lubrication system was sealed through the use of rotary valve shaft seals, and oil recirculated within the system was not introduced into the combustion process. The airplane's experimental operating limitations stated in part, "No person may operate this aircraft unless within the preceding 12 calendar months it has had a condition inspection performed in accordance with appendix D of FAR [Federal Aviation Regulations] Part 43 and was found to be in a condition for safe flight."

The pilot had purchased the airplane in August 2013, and according to the airplane's previous owner, at the time of the sale the airplane's maintenance records were missing and were not provided to the new owner/accident pilot. He also stated that the airplane had not been flown in the four years preceding the sale. FAA registration records showed that a sale of the airplane had been reported, but that no current registration information was on file. According to the accident pilot and current owner of the airplane, the airplane had not undergone a condition inspection in the time that he had owned it, but he had completed some maintenance on the airframe and engine. A review of the logs provided by the pilot showed entries in the airframe and engine logs dated April 19, 2014. According to the engine log entries, the pilot had replaced both spark plugs, replaced the oil in the injection oil tank, performed a compression test of both cylinders, replaced the engine coolant, cleaned and inspected the intake air filter, replaced the gearbox oil, and re-torqued the propeller and cylinder head bolts.

Following the accident, the pilot commissioned an inspection of the airplane's engine and provided a report of the results. According to the report, the engine's rotary valve seal was "completely destroyed." Both of the engine's spark plugs appeared to be "oil fouled," and "substantial" traces of oil were found on top of both pistons, in the intake headers, and on the propeller, as well as the empennage of the airplane. The rotary valve oil tank was empty, and according to the report, had been "topped off" by the pilot prior to the accident flight.

According to the engine manufacturer's published maintenance manual, before every operation of the engine, the oil level of the rotary valve oil tank should be checked. The manual also stated, "In case of notable oil consumption (more than 1 c.c./hour) look for the leak and check the oil seals inside the crankshaft, if necessary." According to the engine maintenance schedule, a general overhaul of the engine should be completed every 300 hours or every 5 years, whichever comes first. The overhaul included an inspection of the rotary valve shaft and replacement of the rotary valve seals.

NTSB 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.