Open your main `server.cfg` and paste these into the bottom. Then modify the settings to your desires. It may take some trial and error to get it exactly how you like.
// Chopper settings
set scr_heli_armor “100”
set scr_heli_armor_bulletdamage “0.3”
set scr_heli_attract_range “4096”
set scr_heli_attract_strength “1000”
set scr_heli_hardpoint_interval “180”
set scr_heli_health_degrade “0”
set scr_heli_loopmax “1”
set scr_heli_maxhealth “100” //value of 1 upto 1300. 1 is easiest to kill, 1300 is default.
set scr_heli_missile_engage_dist “2000”
set scr_heli_missile_friendlycare “256”
set scr_heli_missile_max “3”
set scr_heli_missile_regen_time “10”
set scr_heli_missile_rof “5”
set scr_heli_missile_target_cone “0.3”
set scr_heli_rage_missile “5”
set scr_heli_target_recognition “0.3”
set scr_heli_target_spawnprotection “5”
set scr_heli_targeting_delay “0.5”
set scr_heli_turret_engage_dist “1000”
set scr_heli_turret_spinup_delay “0.75”
set scr_heli_turretClipSize “5” // values of 0 to 40. 0 heli wont fire, but 40 is default value.
set scr_heli_turretReloadTime “1.5”
set scr_heli_visual_range “3500”