What about if the Helicopter was on the ground, I bet spearmen could get it then (you didnt after all specify that the helicopter was airbourne
)
Couldnt throw the spear 2 miles, but nobody said it had to be thrown, maybe it could be fired, some kind of big speargun thing, like a harpoon only bigger
I could think of quite a few ways in which a "spearman" (being unclearly defined) could down a helicopter (being unclearly defined).
Of course if we are talking a wooden spear , thrown only by the arm of a single man, against an airbourne helicopter moving at speed...well thats a different kettle of fish, not sure we're given that specific a set of parameters though.