Hmm. You can create a loop script and play around with the setcamrelpos command...
Do you want me to write you a script?
Aw! Okay then ;D. Since you insisted...
cam1 = "camera" camcreate [0,0,0]
cam1 cameraeffect ["internal","back"]
#loop
cam1 camsettarget ChopperOrPilot (You'll have to check bouth methods)
cam1 setcamrelpos [2,2,2] (You must play around with the values here to get the dezired effect)
cam1 setcamfov 0.7
cam1 camcommit 0
? stop : goto "end"
goto "loop"
#end
exit
Then you can save this as chopper.sqs or whatever you want and exec it from the game.
If stop=true the script will exit.
Just ask for further explanation if you need it!
Good luck! ;D