CEN19LA309

While performing an aerial application flight, the helicopter experienced a partial loss of engine power when the pilot advanced engine power to reverse course. The helicopter was substantially damaged during the forced landing when it contacted trees and landed hard. A postaccident examination of the helicopter’s engine found evidence of fuel contamination due to water and a non-ferrous material in the engine driven fuel pump/filter, fuel control unit, and fuel nozzle. The fuel control unit operated outside of acceptable limits during postaccident testing. The airframe was stored outside and subjected to the elements after the accident; however, the location of the water and debris in the engine were in areas where contamination from the elements cannot normally collect. It could not be determined when the contamination occurred or whether it originated within the company’s fuel truck tank or within the helicopter’s fuel tank.

On September 9, 2019, about 1330 central daylight time, a Bell 206B helicopter, N19TV, was substantially damaged when it was involved in an accident near Walkerton, Indiana. The pilot received minor injuries. The helicopter was operated under the provisions of Title 14 Code of Federal Regulations as a Part 137 aerial application flight. The pilot reported that he ferried the helicopter and landed on the company truck to refuel and add a pesticide mix to the helicopter’s hopper. The pilot departed from the truck and surveyed the field. He completed one pass and added power to reverse course when he heard the helicopter’s engine power decrease. In addition, the low rotor rpm light and horn activated. Due to multiple obstructions on the ground, a normal autorotation could not be performed. As the pilot maneuvered the helicopter to land, the skids and application spray nozzles contacted trees. The helicopter pitched nose down, the main rotor blades damaged the tailboom, and the helicopter landed hard. The helicopter was relocated to a secure facility for further examination where it was stored outside and exposed to the elements. Examination of the helicopter’s airframe did not detect any 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 the housing. The fuel spray nozzle was fouled with a gray particulate matter. Disassembly of the fuel control unit (FCU) revealed the filter was fouled by gray particulate matter along with fibrous material. The FCU was reassembled and tested. Due to the presence of a significant amount of water, the FCU required flushing before testing. Testing of the FCU found that it operated outside of acceptable limits. A review of maintenance logbooks revealed that the helicopter was inspected on January 4, 2019, about 300 hours prior to the accident, using continued airworthiness inspection criteria. Since no evidence of contamination was documented during this inspection, it likely occurred after that date. It could not be determined if fuel contamination originated at the company fuel truck or within the helicopter fuel tank.