Incident Description
A commercial pilot was using a helicopter equipped with a cleaning apparatus to clean electrical power line insulators. During the operation, the pilot reported that the helicopter was hovering approximately 60 feet above the ground when the engine lost power. The pilot turned the helicopter away from the power lines, but the aircraft descended rapidly and impacted the ground. The helicopter sustained substantial damage to the fuselage and rotor system. The helicopter was fitted with a 30-foot articulated spray boom mounted on the right side, a 50-gallon water tank inside, and a pressure pump on the left side. The cleaning equipment was operated by an onboard boom operator.
Examination Findings
An examination of the helicopter revealed that both electric fuel boost pump intakes were clogged with a fibrous material. The electric fuel boost pumps serve as conduits for the engine-driven fuel pump; if they are clogged, no fuel will reach the engine. Similar fibrous material was also found in the airframe fuel filter. The engine was subsequently started and run without issues at a test facility. During a re-examination of the airframe, the fuel tank was cut open, and a triangular-shaped 4-inch piece of an absorbent pad was discovered. The contract fueler had routinely been shoving the fuel nozzle through a hole in the plastic packaging of a bundle of absorbent pads, into the edges of the pads, to prevent fuel from dripping on the tundra. This fueling process was repeated every 7 to 8 minutes.
Cause
Samples of the material taken from the fuel pumps, the piece found in the fuel tank, and an exemplar pad provided by the fuel contractor were sent to a laboratory for testing. The tests revealed that all the samples were essentially identical. The contamination of the fuel pumps most likely occurred when the fuel nozzle tip cut or captured portions of the absorbent pads as it was placed into the pad bundles, and those cut portions were then pumped into the fuel tanks.