Ride of the Valkyrie Achievement
Ride of the Valkyrie25
Get 50 kills with the Huey
Get in any chopper and kill, kill, kill. If you can't fly a chopper get on the side guns so you don't crash and destroy it, they take awhile to re-spawn.
The Huey can be found on the map 'Phu Bai Valley'. Easiest way is Rush as attackers, which is probably easier as the defenders have no tanks to shoot you down. You can change the chopper controls from normal to inverted if that makes it easier for you.
It might help using the V WARHD spec. If you are not good with aiming do it on normal core playlists because hardcore playlists do not have reticules.