Maybe two more little things:
1.)
I really don't like the way the helis fall down after being dead. This turning is somewhat unrealistic especially as they have lost their blades. Maybe when dead you just pin down their direction at that moment in a vector plus calculate their speed and then you give those two properties to the wreckage model and just let a gravity force affect it. The way it is it's just too repetitive (as all will fall in the same manner) and you probably will get problems when you shoot someone at a higher altitude because the heli shot down at 1:38 spins incredibly fast before hitting the water. I think your script makes it spin faster with time but - well as I said I'd prefer a simple "rock falling" technique instead of this spinning (if you want to keep it you should slow down that spinning acceleration a lot)...

2.)
The "dust clouds" the heli creates when getting close to the ground is a very nice detail but it's not done very well I think. To be true I think you put in too much effort here for an effect coming out wrong. You somehow manage to spawn a "ring" of particles whose size depends on the heli's height. I think it would be better if you just trace the position right under the helicopter and from that point you spawn some bigger (maybe animated) dust-cloud particles, which randomly move away in all 360° directions (either you take the world axis for this or you try to calculate the normal vector of the terrain face to have a correct spawning even on tilted terrain). Depending on the altitude you could spawn more of those clouds, make them bigger and faster. This way you have an effect of your heli pushing anything below it away instead of those strange constant circles of dust...

Enjoy your meal
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