What happened
A helicopter was returning to a remote lodge with six skiers on board when the pilot observed the hydraulic pressure warning light illuminate and heard the aural warning horn. This indicated a loss of hydraulic pressure within the system. The pilot confirmed the loss and reduced the aircraft's forward airspeed. In an attempt to restore pressure, the pilot cycled the hydraulic cut-off switch on the collective lever by turning the system off and then back on.
The pilot established a landing pattern and approached a road, bringing the helicopter to a hover above the roadway. During this hover, the aircraft rolled hard to the left and impacted the terrain in an inverted position. There were 6 fatalities involving the passengers and the pilot.
The investigation
An inspection of the aircraft revealed that the hydraulic pump drive belt had separated at the point where the belt is bonded together. This separation caused a total loss of hydraulic pressure. The belt is subject to repeated maintenance inspections and has an operational life limit of 600 hours. At the time of the accident, the failed belt had been in operation for approximately 419 hours.