Incident Sequence
During a positioning flight returning to a hospital base, a flight nurse aboard a single-engine helicopter spotted a herd of antelope and alerted the pilot. The pilot turned the helicopter toward the herd and reduced speed to observe the animals. While maneuvering, the pilot received an engine-out audio warning and observed the corresponding warning light. Noticing a drop in rotor rpm, the pilot checked the engine turbine outlet temperature gauge and determined that the engine had lost power. The pilot reported that he could no longer hear the engine. At an altitude of 500 feet above ground level, the pilot lowered the collective and entered an autorotation. At the moment of autorotation entry, the rotor rpm was in the low 90s. The pilot selected a landing area and instructed the cabin crew that the situation was genuine and to brace for impact. As the helicopter decelerated, the pilot turned the throttle to the off position. Realizing that the helicopter would strike a tree, the pilot raised the collective to cushion the landing. The helicopter struck a tree, then impacted the ground, and came to rest upright in flat desert terrain covered with scrub brush. Photographs taken at the accident site showed open areas devoid of trees surrounding the landing spot.
Post-Accident Examination
An examination of the helicopter found no issues that would have prevented normal operation. A subsequent test run of the engine, which included repeated accelerations and decelerations, revealed no anomalies. The engine's measured power output exceeded new engine specifications. The engine was not equipped with an auto reignition system.