Killzone 3 Walkthrough - Stahl Arms Infiltration: Part 3
Full Walkthrough: http://www.gamefront.com/killzone-3-walkthrough/
You'll enter the factory next. Enemies are lined up on the left, so fire away. Break out your arc cannon to take out the guys on the upper floor as you enter the room, and use it again on the jetpack reinforcements that appear right after you thin out the enemies on the ground floor.
As you advance, another set of jetpackers will appear to take you on. Hit them as they slow or land. You'll find an ammo dump as you advance up to the second floor.
Rounding the corner, you'll find Helghast on the rig across from you on two levels. Use the arc cannon to clear them out quickly (there's an ammo dump ahead on your left), then watch for an additional soldier to come up the elevator at you on the right as you go forward.
At the bottom of the elevator, watch for an RPG trooper on the top floor just ahead of you. Drop him and clear out the others on the ground (can't say enough good things about the arc cannon here).
Advance to an elevator. Right before it is another ammo dump, so fill up before you hit the button to ascend. When you get outside, you'll face a large group of Helghast troops. There are jetpacks on the left if you want them, but you might be better off just taking cover and shooting down on the enemies to the left.
There's not much to the strategy here, especially since you have so much cover. Basically, just sit tight and pick your shots. Let your soldiers help out and draw fire while you put headshots into Helghast troopers. Push down the ramp once you've cleared it, if you want, and take the small building at the bottom. That should wrap up the enemy troops.
Grab ammo in the small building, then sprint back up to your men at the top of the ramp: you're about to fight a flying ATAC, a light artillery vehicle. (Un)fortunately, there's not a lot to this fight, either.
The ATAC likes to hover around at the bottom of the ramp and to the left if you're facing down it, so set up with cover so you're back's to the wall on the right of the ramp. From here, you should be able to hammer the ATAC with your assault rifle or whatever makes you feel comfortable, with little issue.
The only attack that might be worrisome is the ATAC's missile bombardment. Watch for it to lean forward and strafe toward you at a high rate of speed; quickly dodge sideways or sprint clear of your cover to avoid being blown up.
TROPHY: Keep pounding the ATAC and it'll explode before long, giving you the "Go Down and Stay Down" Trophy.
Full Walkthrough: http://www.gamefront.com/killzone-3-walkthrough/