I was a lift operator at Shanty Creek in Bellaire Michigan for four seasons from the late 80's and early 90's..... and both of the antique chairs had very similar evac-backup engines. The "Schuss Mountain" side of the resort got five or six brand-new quad lifts about 10-15 years ago (I forget exactly) ... but the "Summit" side is still using these two antique double-chair Tetanus-despensers.
For the first two years of my employment..... I didn't even
KNOW the lifts had backup engines. But after the resort hired a new outdoor manager (i forget his exact title) this new guy insisted that EVERY lift-operator know how to operate the backup systems. We started the engines every morning and let them warm up. His name was Bob,... his last name isn't necessary, online..... but he was a great guy to work for and still got fired because he knew more about running a ski-resort than the buttwipes who never left the warm offices inside the lodge.
I've never been on the slopes when a chair had to be evacuated.... but I've heard about it, after-the-fact. I think it happened three times during my first two years as a lift-op. Ski-Patrol had to spend about three or four hours with cables and pulleys evacuating EVERYBODY from the chairlift during high-wind conditions during power outages and such. I still find it hysterical that all they needed to do was start the backup engines and shift into "Drive"......... but it took this "New Guy" to introduce us to the gas engines that no-one knew were there.
I love spark plugs.
Love 'em.
.....(And carburetors,..... can't forget the carburetors).
Silence is golden,..... Duct Tape is silver.