Faulty Switch Contributed to Sugarloaf Lift Rollback

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SAM Magazine—Carrabassett Valley, Maine, March 26, 2015—A team of investigators has determined that an inappropriately specified switch in one of the brake components on Sugarloaf's King Pine lift contributed to the March 21 rollback accident that injured seven people.

Officials from Sugarloaf and engineers from parent company Boyne Resorts said that one of the switches used in the safety circuit connected to the drop dog—a final system intended to automatically engage to prevent a lift rollback—was not the correct switch for the intended application. The switch is designed to suspend the drop dog above the bullwheel when it senses forward rotation or deploy it when the lift rotates in reverse.

Engineers said that had an appropriate switch been included in the system, the drop dog would have deployed and the rollback would have stopped immediately. The switch was provided by Borvig, the lift's original manufacturer, and is still provided by the company that manufactures components for this type of lift. As a result, the flaw may well affect other Borvig installations across North America.

A licensed Maine lift inspector has since reviewed and approved new circuitry designed by Sugarloaf engineers to correct the situation. Six lifts at Sugarloaf use similar components, and all were temporarily shut down on Wednesday for modifications. The same procedure was followed on similar lifts at sister Boyne resort Sunday River as well. Officials from Sugarloaf said they have been in touch with the lift's parts manufacturer regarding the situation.

Previously, investigators reported that a shaft in one of the two gearboxes that transfer power from the lift's electric motor to its bullwheel fractured, initiating the rollback. However, they said that the failure of the shaft, in and of itself, should not have resulted in the rollback if the lift's remaining systems had performed as intended.

The fracture of the shaft resulted in the loss of both the primary service brake and the anti-reverse brake, leaving two additional braking systems intended to prevent a rollback. Officials said the lift's automatic bullwheel brake engaged and operated properly. Additionally, they said the lift operator quickly activated a manual control to apply the bullwheel brake.

In the time between bullwheel brake activation and the actual stoppage of the lift, the lift traveled backwards for a total of nine chair lengths, or approximately 460 feet, due to the weight of skiers on the lift, which was full.

The gearboxes in the King Pine lift, along with every other lift at Sugarloaf, were subjected to a routine vibration assessment by an outside contractor the day before the incident. No anomalies were detected that indicated such a fracture was imminent or likely. The investigation by the State of Maine Board of Elevator and Tramway Safety remains ongoing.