Witness Observation
A witness reported observing the helicopter flying at a high speed in a southerly direction at an altitude of approximately 500 to 600 feet above ground level. Flames were visible emanating from the right rear side of the helicopter in the area of the engine compartment. Very little smoke was observed. The helicopter appeared to be in controlled flight before it descended from view.
Accident Sequence
Subsequently, the aircraft impacted the ground and was destroyed by a fire that occurred both in flight and after impact.
Examination Findings
Examination of the engine compartment revealed localized bluing on the step portion of the forward firewall where the throttle and fuel line pass through. However, the fuel line connector, which remained attached to the firewall fitting, did not exhibit any fire damage.
The #3 tail rotor drive shaft segment was located 66 feet prior to the initial impact scar. The shaft was fractured, with fire-damaged fiberglass cloth wrapped around the forward end of the fractured shaft.
According to a National Transportation Safety Board metallurgist, the fracture was consistent with overstress after exposure to elevated temperatures.
Background
The helicopter was returning to Guatemala after completion of scheduled maintenance performed in the United States.