Incident Overview
A helicopter departed from an offshore platform and, as it accelerated through 40 to 50 knots in a slight climb at about 200 feet from the platform, the pilot heard and felt a loud bang. The helicopter's tail yawed to the right, and the aircraft began to descend. The pilot issued a mayday call and prepared for a water landing. The helicopter touched down in a nose-high attitude, and the tail rotor system contacted the water. The emergency flotation system deployed successfully, and both the pilot and passengers reported a smooth water landing.
Engine and Aircraft Examination
A detailed examination of the helicopter's engine was conducted at the operator's maintenance facilities. Investigators found no evidence of distress or failure in the compressor, engine gearbox, or turbine assemblies that could explain the loud bang reported. Additionally, no unresolved engine-related discrepancies were found in the aircraft or engine records.
Tail Rotor Blade Analysis
The operator reported that a section of a tail rotor blade was discovered on a beach miles from the accident site, and it was verified to be from the accident helicopter. The blade fragment was sent to a laboratory for analysis. Examiners found marks on the leading edge of the blade, extending approximately thirteen inches from the tip, appearing evenly spaced. The fracture was determined to be the result of overload. Transferred material on the blade was analyzed and confirmed not to originate from any part of the helicopter. The material was identified as possibly stemming from the metal bindings of a notebook.
Investigation of the Notebook Binding
The suspected three-ring binder was not located. None of the three helicopter occupants reported losing a three-ring binder. The manager of the offshore helideck stated that there were no loose objects on the helideck and that foreign object debris (FOD) sweeps were conducted routinely. The source of the missing binder could not be established.
Conclusion
The investigation did not identify a definitive cause for the loud bang or the tail rotor blade fracture. The likely involvement of a notebook binding was suggested by material analysis, but the origin of the binder remains unknown.