http://gtaxscripting.blogspot.com.br/2013/03/script-heli-combat.html

Features:

Custom weapon number and position
Custom cameras
Up to 4 Cannons
2 Hellfire launchers
8 Rockets with lock on feature (lock on any vehicle)
2 Gunner position on chopper
Spawn menu
Enemy helicopter

v1.2:






v1.1

Fixed bug with patch version .4 (i hope)
Fixed enemy heli exploding after killing player
Fixed enemy aim method
Added train derail feature
Added flares (Hotkey E)
Fixed Cannon fire rate
Fixed gunner initial camera rotation
and some other little things