Accident Overview
On October 24, 2017, about 1540 central daylight time, a Bell 206B helicopter, registration N60EA, sustained substantial damage during a forced landing following a total loss of engine power while on approach to a private landing zone near Groom, Texas. The pilot was not injured. The helicopter was owned and operated by Plains Aerial Leasing, Inc as a Title 14 Code of Federal Regulation Part 137 agricultural aerial application flight. Visual meteorological conditions existed near the accident site, and no flight plan was filed. The flight had departed from an off-airport landing zone about 1515.
Pilot's Account
The pilot reported spraying fields all day before the accident. After completing a field, he had the helicopter loaded with chemical and refueled from the operator's load truck without shutting down the engine, a practice known as "hot refueling." The fuel gauge indicated 20 gallons on departure. He flew to a 43-acre field about 8 miles away and began spraying, performing steep turns. After dispensing all chemical, he made a steep "hard right turn" en route to the operator's base, about 3/4 mile west. About 40 seconds later, with the fuel gauge showing 10 gallons, the helicopter was on approach. While on a right base leg about 40 feet above ground level and 35 knots airspeed, the pilot felt a "tail wag," and the engine stopped producing power. He performed an autorotation, but the tail impacted the ground during flare, resulting in substantial damage.
Post-Accident Examination
A Federal Aviation Administration (FAA) inspector examined the helicopter at the accident site. The engine showed no apparent anomalies; the short shaft turned freely manually. The P3 line was intact and secure with no visible cracks. Examination of the flight control system exhibited continuity; breaks were consistent with overload fractures.
Fuel System Inspection
The fuel quantity and pressure gauges worked properly. The fuel gauge indicated about 7 gallons remaining; fuel pressure showed 2 psi. Draining the airframe fuel filter yielded about two spoonsful of fuel. With fuel boost pumps on, the pumps initially sounded like cavitating, and about 7 gallons of fuel were drained, free of contamination and water.
The engine was removed and tested at a facility. After visual inspection, it was placed on a test cell and started. It completed ground-idle, flight-idle, max-continuous-power, and take-off power runs, as well as "wave-off" max-power transients, responding normally without surging or hesitation.
Flight Manual References
The Bell 206B Flight Manual states that a FUEL LOW light (if installed) illuminates with about 20 gallons remaining, advising "Land as soon as practical." The accident helicopter did not have this caution light installed. Total fuel capacity was 96.7 gallons. A warning notes: "Operation with both fuel boost pumps inoperative is not authorized. Due to possible fuel sloshing in unusual attitudes or out of trim conditions and one or both fuel boost pumps inoperative, the unusable fuel is 10 gallons." Another warning states: "One or both fuel boost pumps is inoperative. Descend to below 6000 feet pressure altitude if flight permits. Land as soon as practical." An associated note explains: "The engine will operate without boost pump pressure under 6000 feet pressure altitude and one boost pump will supply sufficient fuel for normal engine operations under all conditions of power and altitude. Both fuel pumps shall be ON for all normal operations."
The pilot stated he pushed the fuel boost pump circuit breakers in when starting the engine for the first flight of the day and pulled them out when shutting down at day's end. He conducted hot refueling without shutting down. He confirmed the boost pump circuit breakers were in during the accident flight. He also stated he would pull the caution light circuit breaker to silence the low rotor rpm warning horn during ground operations. Both boost pump circuit breakers and the caution light circuit breaker had blue collars for easy identification.