I'm stuck.

There is a level where your team storms a castle in the Chilean desert of South America. Inside the upper courtyard, you get swarmed by attack helicopters. I try using the mounted rocket launcher, which are effective when you can get a good shot off. Takes 3 it hits it looks like though. In practice though, they're worthless - traverse speed is uselessly slow, and elevation traverse is so low you can't aim up high enough half the time. Shoulder launched rockets aren't very effective, and you can't hide that I can tell. So it's pretty much load/die load/die for the last hour. Getting annoying.

Is there a trick to this I'm missing?