Another chairlift at Sugarloaf ski resort malfunctioned this weekend by going backward, prompting some frightened skiers to bail out and raising questions about the safety of aging infrastructure at New England’s ski resorts.

The resort said Sunday a preliminary investigation found that a gearbox on the lift malfunctioned and effectively disabled two brake systems. A third backup brake also didn’t deploy properly and a lift attendant pulled an emergency brake to bring it to a halt after chairs slid about 450 feet, Sugarloaf spokesman Ethan Austin said in an emailed statement.

A rollback refers to an incident in which the chairlift travels backwards. The rollback did not cause the lift to de-rope. The lift rolled back a distance of nine chairs.

The King Pine Quad is a 4 passenger monocable fixed grip quad built in 1988 and manufactured by Borvig. It is located on the eastern side of the mountain. King Pine is 3,400 feet long with a vertical of 1,074 feet. The chair moves at a speed of 450 feet per minute and the chairs are roughly 51 feet apart. There are a total of 122 chairs on the lift, which is powered by a 400 horsepower motor. It has a transportation capacity of 2,100 skiers per hour.

Seven skiers were hurt at the resort. Two of the three injured skiers transported to a hospital 40 miles away were treated and released. A third skier was transported to another hospital, a hospital spokeswoman said Sunday. The condition of the third skier was not known, but the resort said the injuries were not believed to be life threatening.

Previously at Sugarloaf, a December 2010 incident involved a 35-year-old double chairlift – since replaced – that was being worked on while skiers were on board. Saturday’s incident involved a 27-year-old quad chairlift. See Sugarloaf Ski Accident Investigation.

The King Pine lift that malfunctioned over the weekend had passed its annual state inspection and a dynamic load test that’s required every seven years last fall, according to the resort spokesperson. The gearbox that failed, effectively blocking two of the three brake systems from deploying, had just received preventative maintenance the day before, he said, adding that it’s too early to know if procedures will be changed.

According to Sugarloaf, Monday, March 23: “The gearbox failure effectively decoupled the bullwheel from the lift’s primary service brake, which is located on the drive shaft between the two gearboxes, and its anti-reverse brake, which is the first of three redundant backup mechanisms for preventing reverse travel.

“Just one day before the incident, the gearbox passed a sophisticated routine preventive maintenance procedure intended to identify potential problems.

“At this point, the emergency bullwheel brake, which uses calipers to apply braking pressure to the flange of the bullwheel itself, was applied by the lift attendant. 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.

“The final braking mechanism, known as a drop dog (a large metal pin that drops into the bullwheel to prevent rotation), apparently failed to deploy as designed. Lift mechanics routinely check gearbox oil levels as part of their daily pre-operating checklist. But much like an automobile transmission, the machinery inside of a lift gearbox is not easily observed, so Sugarloaf contracts for routine maintenance tests that can indicate potential problems before they occur.

“The gearbox last underwent major servicing, including the replacement of worn components, just before the start of the 2011-2012 winter season. The work was performed by a contractor who specializes in gearbox maintenance.”

So this extensive detailing of resort maintenance on the lift begs the question as to why the braking system failed so completely. In light of all that maintenance, one must ponder if perhaps some ski lifts are just too old to not fail.

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