Which coast guard?
Are you thinking of Bear Trap? Canadians use it a lot:
http://www.alexisparkinn.com/photoga...gs_on_Deck.wmv
"The helicopter lowers a line that attaches to the bear trap. When the line is attached, the helicopter applies power to create tension on the line. This prevents the helicopter from colliding with the ship as it is "winched" onto the flight deck. "
Lynx has a harpoon fixed to the belly to lock into a grid for stability.