Accident Narrative
On September 9, 2019, at approximately 1330 central daylight time, a Bell 206B helicopter, registration N19TV, sustained substantial damage during a forced landing near Walkerton, Indiana. The helicopter was being operated as a Part 137 aerial application flight. The pilot reported minor injuries.
The pilot had ferried the helicopter to a company truck for refueling and addition of pesticide mix to the hopper. After departing the truck and surveying the field, the pilot completed one pass and initiated a turn by adding power. During the turn, the pilot heard a decrease in engine power, and the low rotor rpm warning light and horn activated. Due to multiple obstructions on the ground, a normal autorotation could not be performed. While maneuvering to land, the skids and application spray nozzles contacted trees. The helicopter pitched nose down, the main rotor blades struck the tailboom, and the helicopter landed hard.
Examination Findings
The helicopter was moved to a secure facility for examination and stored outdoors, exposed to elements. Examination of the airframe revealed no preimpact anomalies. The engine was removed, disassembled, and examined. Gray fibrous material was found trapped in the engine-driven fuel pump/filter. The outer portion of the filter was contaminated with black, non-ferrous particulate matter, and the inside contained a white greasy substance. Fluid did not transfer through the filter when it was removed from its housing. The fuel spray nozzle was fouled with gray particulate matter. Disassembly of the fuel control unit (FCU) revealed its filter was fouled by gray particulate matter and fibrous material. The FCU was reassembled and tested; due to the presence of a significant amount of water, it required flushing prior to testing. Subsequent testing showed the FCU operated outside acceptable limits.
Maintenance History
A review of maintenance logbooks indicated the helicopter underwent an inspection on January 4, 2019, about 300 flight hours before the accident, using continued airworthiness inspection criteria. No evidence of contamination was documented during that inspection, suggesting the contamination likely occurred after that date.
Fuel Contamination Origin
It could not be determined whether the fuel contamination originated at the company fuel truck or within the helicopter's fuel tank.