Incident Overview
While returning to a remote lodge with six skiers, the pilot of a helicopter observed the hydraulic pressure warning light and heard an aural warning, indicating a loss of hydraulic pressure. The pilot confirmed the loss and reduced forward airspeed.
Pilot Actions
The pilot cycled the hydraulic cut-off switch on the collective lever, briefly turning the system off and back on. He then entered a landing pattern, approached a road, and brought the helicopter to a hover above the roadway. Upon reaching a hover, the helicopter rolled sharply to the left and struck the terrain in an inverted position.
Manufacturer Guidance
According to the helicopter's operator manual, the proper procedure for a loss of hydraulic pressure includes reducing collective pitch to decrease airspeed, disengaging the collective pitch hydraulic pressure switch, conducting a flat approach, and performing a landing with forward airspeed.
Post-Accident Findings
An examination of the helicopter determined that the hydraulic pump drive belt had separated at the point where the belt was bonded together. This belt failure resulted in a complete loss of hydraulic pressure. The drive belt was subject to recurrent maintenance inspections and had a service life limit of 600 hours. The belt on the accident helicopter had accumulated approximately 419 hours of operation since installation.