Destroy 10 choppers using the Javelin Launcher in 'Of Their Own Accord'.

When you get to the area where there's a few enemies and one of them is holding a Javelin you'll want to take them out. In this room there are two Javelins, make sure to pick up one in the right corner. Then you will want to pay attention to the green arrows that are on either side of your screen as it tells you which direction the helicopters are flying.




Achievement is worth 30 gamerscore.