It's the most inconsistent weapon when locking on. Some times it beeps for 3 seconds, other times for 8. You fire it and every once in awhile it'll show a missile come out, but you lose no ammo as if it never shot. Then if the pilot has half a brain they can dodge it easily, not to mention they have an unlimited amount of flares.
Even if you do manage to hit a helicopter, they fly away and have auto repair or just have 2-3 guys repairing while they're being hit. No one when else in this game seems to even try to shoot them down with. I just bought the game on PC hoping with more people we could accomplish more. Nope, just another 15 snipers out in a field setting down a beacon spawn 500 feet away from a flag lol.
I seriously can't see a reason to use this weapon. We'd have a helicopter over our spawn getting killed. 3 people would shoot at it and it just absorbed all of our stingers until we had none left since it was constantly being repaired. Shouldn't you have to land the thing to fix it?