CARRABASSETT VALLEY — Workers at Sugarloaf are investigating what caused a gearbox and braking system for the King Pine Quad chairlift to fail Saturday.

The failure caused the lift to roll about 450 feet backward, resulting in seven people being injured, including three who were taken to a Farmington hospital. More than 200 people were taken off the lift.

Two were treated and released from Franklin Memorial Hospital as of Sunday, and one was transferred to Central Maine Medical Center in Lewiston. That person’s condition was not available. All three had noncritical injuries, an FMH spokeswoman said in a news release Sunday. The others injured were treated at Sugarloaf.

“The first step for us in preventing a future accident like this is to investigate what caused this to happen in the first place,” Ethan Austin, Sugarloaf director of marketing, said Monday. “Our team is working tirelessly to investigate the root causes of the equipment failures … Our lift maintenance team will also continue to rigorously test and inspect all of our lifts, which they do on a daily, weekly, monthly and yearly basis.”

The U.S. Alpine Ski Championships will take place at Sugarloaf from Wednesday through Sunday, attracting the best skiers in the country, including Lindsey Vonn and Mikaela Shiffrin.

“King Pine being offline won’t affect the championships at all,” Austin said.

Sugarloaf investigators are working in conjunction with John Burpee, the state’s chief tramway inspector.

The lift will remain closed pending further investigation.

While the investigation is ongoing, preliminary findings revealed that the “trigger for the incident was a major mechanical failure in one of two gearboxes connecting the lift’s electric motor to its drive bull wheel,” according to information provided on Sugarloaf’s website by Austin.

A bull wheel is a large, metal wheel on which the lift cable that supports the chairs is tensioned, he said.

“Just one day before the incident, the gearbox passed a sophisticated routine preventive maintenance procedure intended to identify potential problems,” Austin stated. “The gearbox failure effectively decoupled the bull wheel from the lift’s primary service brake, which is located on the drive shaft between the two gearboxes, and its anti-reverse break, which is the first of three redundant backup mechanisms for preventing reverse travel.”

At this point, the emergency bull wheel brake, which uses calipers to apply braking pressure to the flange of the bull wheel itself, was applied by the lift attendant, he said.

“This brake slowed the speed of the rollback and ultimately brought the lift to a stop. The application of the emergency brake by the lift attendant likely prevented a more extensive rollback,” Austin’s website posting stated.

“The final braking mechanism, known as a drop dog, a large metal pin that drops into the bull wheel to prevent rotation, apparently failed to deploy,” he said.

“Although problems with any mechanical system can happen, the safety track record of chairlifts in Maine is quite good,” he said.

The gearbox last underwent major servicing, including the replacement of worn components, just before the start of the 2011-12 winter season, Austin said in his news release. The work was performed by a contractor who specializes in gearbox maintenance, according to Austin.

An oil analysis was done on the King Pine lift on Jan. 19, and a vibration analysis was conducted Friday, a day before the accident occurred. Lift operators also do daily preoperating checks.

It is unknown how the breaking system could fail with two recent inspections and maintenance done the day before, Austin’s information said.

“We don’t have the answer to that question yet, but are working around the clock to get it. Discovering the root causes for the mechanical failures in the lift is focus of the accident investigation going forward,” Austin said.

All chairlifts in Maine must pass a state inspection prior to being put into operation for the ski season, Doug Dunbar, spokesman for the Maine Department of Professional & Financial Regulations, said Monday. This inspection leads to a certificate of operation being issued.

King Pine passed its annual inspection last fall.

According to the state’s online licensing information, the quad was installed in 1988. A new drive was installed and load-tested on Oct. 25, 2007. The annual state inspection of the lift was done Oct. 14, 2014. The license expires Dec. 31, 2015, but another inspection is scheduled for November.

“No reports of problems, complaints or concerns about King Pine have been received by the department since that inspection,” Dunbar said.

“At this early point in the investigation, it appears the problem occurred in the gearing system that transmits power from the electrical motor to the bull wheel,” he said.

All ski areas must have a quality control program, which includes and documents additional checks and maintenance beyond the annual state-required inspection, he said.

This quality control program for all ski areas includes greater specificity and requires more detailed documentation since a chairlift incident at Sugarloaf in 2010. At that time, five chairs on the Spillway chairlift fell about 30 feet in December 2010. Of the 10 people who fell to the ground, eight were injured. A lawsuit is awaiting trial in that case.

dperry@sunmediagroup.net