Primary finding
Probable cause
An elevated oil temperature and subsequent total loss of engine power for reasons that could not be determined based on the available information.
Investigator assessment
Analysis narrative
The private pilot of the experimental, amateur-built airplane reported that the purpose of the flight was to evaluate the effect of airstream cooling on the engine oil temperature once the airplane reached level flight. He stated that departure, climb, and level-off were uneventful; however, while maneuvering, the oil temperature began to increase. A descent did not mitigate the increase in oil temperature, and the engine subsequently experienced a total loss of power. The pilot attempted to restart the engine; when it did not respond, he began a right turn toward the departure runway. The airplane touched down short of the runway and collided with a fence. The pilot sustained a serious head injury and did not recall anything after the turn toward the airport. The experimental engine was not made available for examination after the accident, and the reason for the elevated oil temperature and subsequent loss of engine power was not determined.
Source record
Factual narrative
The engine was an experimental Aeromaxx BB420 H, serial number 11U, rated at 118 hp. Aeromaxx used their own remanufactured and restored Corvair parts to build Corvair engines for homebuilt, experimental aircraft. The experimental engine was not available for an exam. On May 29, 2015, about 1100 mountain daylight time, an experimental amateur-built Pulsar III, N747N, collided with corral fences during an emergency off airport forced landing at Hurricane, Utah. The private pilot sustained serious injuries; the airplane sustained substantial damage. The pilot/owner was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The local personal flight departed General Dick Stout Field (1L8) in Hurricane about 1000. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot reported that the purpose of the flight was to evaluate the effect of airstream cooling on the engine oil temperature once the airplane reached level flight. The plan was to circle above the airport while climbing to the desired altitude, establish level flight, observe the oil temperature, and land. After takeoff, climb performance and oil temperature were normal. At 5,100 ft msl (airport elevation was 3,347 ft), the pilot began to circle the airport. After three circles, he noticed that the oil temperature was about 220° F, and he began a shallow descent to help cool the engine. About 4,500 ft, the oil temperature was about 230° F, and the engine shut off. He turned on the auxiliary fuel pump, and attempted to restart the engine. When it did not respond, he began a right turn towards runway 19 at 1L8. The airplane touched down short of the runway, and collided with the corral fences. The pilot sustained a serious head injury, and did not recall anything after the turn toward the airport. One witness stated that he had observed the takeoff, and watched the airplane complete two climbing turns. He heard a radio transmission from someone asking the pilot if everything was alright. The pilot replied no, he was "dead sticking," which meant to the witness that the engine was not running. The witness observed the airplane was about 1/2 mile from the airport, and the propeller was not turning. He lost sight of the airplane just prior to touchdown.