Also tried going prone in small house with door closed. Helicopter spots you. I even blew up the truck I drove to the site with.

FYI for anyone with the same problem, one of the CSAT near the windmills has an AA launcher you can use to take out the helicopter even when it inevitably spots you.

I too have this problem. Hid in bushes and I was the only member of my squad left. The helicopter ALWAYS spots you.

Whoops. Okay, ignore the part about "Stream friendly UI." The rest of the issue is still valid.