Dear Stales: Rappeling and abseiling are both means of descending in a controlled manner. The abseil mentions use of a figure of eight. I gather that the rope goes about the person in a way that rate descent can be controlled, but can't imagine how the user prevents fouling or excessive tightness.Or worse still, sudden loss of control.
The chimney down through the ice apparently gave very little freedom of movement.
I haven't finished the article yet, so don't yet have any idea how they were able to dig a chimney big enough to lift the plane straight up two hundred and fifty feet! Incidentally, that means the planes sank five feet a year, meaning the ice isn't as solid as you might think.That's almost two tenths of an inch per day.