Well i can proudly say i got my first Helicopter kill with the UAV earlier 
Was epic, was flying straight as i shot it from the side and the rocket just curled round and up into the bottom of the chopper and blew it up before they could even bail.
Also the Smoke grenades the UAV uses are damn forceful when you hit a chopper mid flight with them. Not done it in a real situation but i hit Squarks tail with them on my team and the chopper almost fell over sideways (before crashing since he was hovering over the ground).
You probably got teamswapped (or they did) mid life. Its really irritating when your killing the enemies, then suddenly your own team blasts you in the back... Its also really irritating when it swaps you when you're doing well. Tefal, Rifle, Squark and me were slaughtering the other team on Cold War, then on the last 2 points as we armed 1 point and killed a load of there team so the crap players on our team could push up then suddenly our entire squad got teamswapped.

Was epic, was flying straight as i shot it from the side and the rocket just curled round and up into the bottom of the chopper and blew it up before they could even bail.
Also the Smoke grenades the UAV uses are damn forceful when you hit a chopper mid flight with them. Not done it in a real situation but i hit Squarks tail with them on my team and the chopper almost fell over sideways (before crashing since he was hovering over the ground).
You probably got teamswapped (or they did) mid life. Its really irritating when your killing the enemies, then suddenly your own team blasts you in the back... Its also really irritating when it swaps you when you're doing well. Tefal, Rifle, Squark and me were slaughtering the other team on Cold War, then on the last 2 points as we armed 1 point and killed a load of there team so the crap players on our team could push up then suddenly our entire squad got teamswapped.