Primary finding
Probable cause
A total loss of engine power due to a binding drive belt while in the airport traffic pattern.
Investigator assessment
Analysis narrative
The pilot reported that she was on a postproduction check flight of a recently completed experimental homebuilt airplane. She said that while on the downwind leg in the traffic pattern, the engine sputtered, the cylinder head and exhaust gas temperatures began to rise, and the engine lost power. During the subsequent emergency descent, the airplane struck a power pole and power lines, and then flipped and impacted the ground tail first. Postaccident examination of the engine revealed that one of the two drive belts for the gear reduction drive had fallen off of the pulley and showed evidence of binding.
Source record
Factual narrative
On July 7, 2012, about 0920 Alaska daylight time, a homebuilt experimental Preceptor STOL King airplane, N919WP, sustained substantial damage during a forced landing, following a loss of engine power while in the traffic pattern at Lakloey Air Park, North Pole, Alaska. The airplane was being operated by the pilot as a visual flight rules (VFR) personal flight, under 14 Code of Federal Regulations Part 91, when the accident occurred. The certificated private pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed. During an on-scene interview with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on July 7, the pilot stated this was the second test flight since the aircraft was completed. She had departed Lakloey Air Park, and was staying in the traffic pattern. On the downwind leg, the engine sputtered, cylinder head and exhaust gas temperatures began to rise, and the engine lost power. During the emergency descent, the airplane struck a power pole, hit power lines, and impacted the ground tail first. The airplane sustained substantial damage to the empennage and wings. The examination of the engine, by the NTSB IIC, revealed one of the two drive belts for the gear reduction drive had fallen off the pulley, and showed evidence of binding.