[Mobhack]

If helos get close enough to infantry they can fire at them - assume that if the infantry fire does a lot of damage that an RPG may have been part of the response.

It has also been a while, but I seem to recollect that a landed chopper is a soft target like a truck for ground weapons. So an RPG team if in range could splat such as it is landing troops. But if landing infantry inside RPG range of defenders, something has gone pear-shaped anyway for the choppers..