Lift rollback investigators issue preliminary findings

CARRABASSETT VALLEY – A team of investigators have completed a preliminary review and investigation of the rollback of the King Pine Chairlift on Saturday, March 21.

Seven skiers were injured after the King Pine quad chairlift slid backwards at 11:30 a.m. Saturday morning, in what is commonly referred to as a rollback. Three people were transported by ambulance to Franklin Memorial Hospital in Farmington. A hospital spokeswoman there said two adults were released after treatment and a third adult was transferred to Central Maine Medical Center in Lewiston for further treatment. Sugarloaf described the injuries as non-life threatening.

In a two-hour rescue operation by ski patrollers and firefighters, 204 chairlift riders were evacuated.

Investigators, including Sugarloaf personnel, engineers from Boyne Resorts and a licensed Maine lift inspector, determined that a fracture of the main drive shaft of the lift’s secondary gearbox initiated the rollback, according to Sugarloaf spokesman Ethan Austin in an email Wednesday. While the lift’s bullwheel brake engaged and operated properly, investigators found, another device failed to deploy due to a design flaw that has since been corrected.

“Our first thoughts remain with those injured, and our sincere hope is for their speedy recovery,” Sugarloaf General Manager John Diller said Wednesday. “I’m grateful that we now have a clearer understanding of what occurred.”

Preliminary findings of the investigative team indicate that a shaft in one of the two gearboxes that transfer power from the King Pine chair lift’s electric motor to its bullwheel fractured. That fracture resulted in the loss of both the primary service brake and the anti-reverse brake, leaving two braking systems designed to prevent a rollback.

“The gear boxes 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,” Austin said Wednesday, “and no anomalies were detected that indicated such a fracture was imminent or likely.”

The failure of the shaft  should not have resulted in a rollback, Austin noted, if the lift’s remaining systems had performed as intended.

According to investigators, the bullwheel brake, an automated, emergency braking mechanism, functioned correctly. Furthermore, the lift operator “quickly activated” a manual control that also would have activated the bullwheel brake. That brake is not instantaneous by design, to prevent sudden movement that might cause skiers to fall out of the chairs or potentially derail the lift, but instead slows the lift to a stop. The 460 feet of rollback was the equivalent of nine chair lengths.

Investigators found that another device, known within the industry as a “drop dog,” failed to prevent the rollback due to an apparent design flaw. While the drop dog is designed to prevent the lift from counter-rotating, the investigation revealed that a switch that should have deployed the device did not function correctly.

“This switch, which is designed to suspend the drop dog above the bullwheel when it senses forward rotation of the lift, can also suspend the drop dog when the lift rotates in reverse,” Austin said. An appropriate switch, he noted, would have deployed the drop dog and stopped the rollback.

Personnel with Sugarloaf, Boyne Resorts and a state lift inspector have designed new circuitry to correct the issue. The modification, which replaces the switch designed by the original lift manufacturer, has been approved by the state and since installed in six other Sugarloaf lifts: Skidway, Sawduster, Snubber, Double Runner East, Double Runner West and Bucksaw. Those lifts were temporarily closed until the modifications are complete; Bucksaw will likely open Friday.

Sugarloaf and its parent company have been in touch with the lift’s parts manufacturer to share their findings regarding the drop dog switch.