I'm doing background research on a real application. At high altitudes (and/or when people are shooting at you) helicopters can't stop and hover, but could snag a survivor or critically injured litter patient at around 30 knots (15 meters per second) A similar device (Fulton Recovery system) has been used from airplanes at over 100 knots (see James Bond/Green Beret movies). Just to check my math, this would be the same equation as a ballistic pendulm. A 15 M/sec speed would result in the survivor swinging to a maximum height of 11.48 meters, with the maximum G load based on the cosine of the length of the line. A line 23 meters long wouls result in a 2G max load. The design would be trainling a line with a hook, rather like a fighter's tail hook, which would snag a loop held horizontal above the survivor.