what u have to do is to shoot at the region enclosed by the orange line
(look at picture1)
(you have to face the front of the helicopter in order to shoot at that region,
sometimes the heli might be too close to you, if this happens, just run away a little bit from it and you can see and shoot at that region)
this should work no matter the helicopter is moving or not
but of course shooting at correct region when it's moving is harder
picture1 (click to enlarge)
direct link: http://g.imagehost.org/0830/2_15.jpg
(maybe shooting somewhere near the region enclosed also work, but i don't know detail about it, need to be tested)
pic2 (1 shot & the heli will go out of control, crash into something & explode)
with this trick, you can possess other slot 9 weapon (other than rocket launcher) without needing to worry about the police heli, as you can always use a slot 10 weapon(sniper type) to destroy it quickly!
note: other normal method for destroying police heli:
shoot heli with:
m60: take 36 ammo
minigun: take 176 ammo
(hard to believe, as minigun does more damage as stated in the weapon.dat!)
rocket launcher: 1 & for all...
other weapons: take even more ammo i believe, not to be attempted......
sub-machine guns (eg. mp5,uzi) : 180 ammo
grenade with detonator/rocket from tank cannon: hell, it seem the police heli is immune to them
edit: new finding: shooting at other region also works
Edited by p3v, 07 August 2009 - 07:26 AM.