What happened
The pilot was conducting an airborne seismic survey in a 1995 model helicopter at approximately 150 feet AGL when the engine suddenly lost power. In response to the power loss, the pilot lowered the collective and turned the aircraft into the prevailing 10-knot wind. As the pilot performed the flare for an autorotation landing, the rotor RPM decayed, causing the helicopter to touch down hard. There were no injuries reported in the accident.
The investigation
Investigators examined a fuel sample taken from the fuel filter sump, located between the fuel tank and the throttle body of the fuel-injected engine. This sample contained a substantial amount of water. Following this finding, FAA inspectors and the helicopter operator inspected the fuel storage tank used for refueling the aircraft. An examination of the fuel filter within the trailer-mounted tank revealed the presence of both water and rust.