Call of Duty: Black Ops Achievements

First, get to the Valkyrie rockets. Now run back to where you landed after falling from the chopper. Lure the helicopters to the pad where your standing, now if you fail this next bit, kill yourself to restart. Line the helicopters up and fire the rocket, get it inbetween both helicopters and press RT again to make it explode. If done correctly, it should take both of them down. OR you can get fancy and hit one helicopter into the other. Either way will get you the achievememt.