Incident Description
During a cruise at 2,000 feet MSL and 150 knots, the crew heard a loud noise. Simultaneously, the helicopter yawed approximately 30 to 40 degrees to the right and pitched nose down. The aircrew initiated an autorotation and deployed the emergency floats. Throughout the descent, the helicopter continued in a right descending turn.
Emergency Landing and Rescue
The helicopter touched down on Lake Michigan with a forward speed of about 40 to 50 knots. After contacting the water, the helicopter turned an additional 180 degrees and then listed approximately 10 degrees to the left. The occupants donned their life vests and exited the helicopter. Approximately 11 to 13 minutes after landing, the aircraft rolled over in the water and eventually sank. All occupants were rescued before the helicopter sank.
Investigation Findings
An investigation revealed that the left side tail rotor cable, part number 76400-03191-043, had failed at a location where it had been rubbing. The rubbing was attributed to incorrect routing of the cable.