The best way to get this trophy is during "Crash and Grab" after leaving the Monastery. Once you get back down to the dam to get into a boat, cross the dam and then climb the metal steps to get on top of the building where a laser designator is located. For best results, get inside the building and aim the laser on the chopper. It will be pounding you mercilessly. Just before you control the bomb, you should be able to hide back in the building to keep you alive. Steer the bomb to the helicopter. It might take you a couple of times to hit it.