Mission 9 The Only Easy Day... Was Yesterday
Half way through the mission a helicopter will spawn in. Run back from where it spawned and it will follow you, isolating it in a 1v1. Now just time your grenade throw to explode the helicopter. Playing on recruit is highly recommended as the helicopter will easily kill you on harder difficulties. reload the checkpoint as needed.
Here is a video guide with English commentary!
Here is a playlist of guides for this game!https://www.youtube.com/playlist?list=PL-HeW6XkKdUK97oYVSMU7...