If you are doing aerial filming you would want to set the focus to infinity (mountain icon).
Also, it is a good idea to have a shutter speed higher than 1/500th of a second to reduce the effect of the vibrations. The higher the better. You will need to use shutter speed overrides to achieve this. If the weather is slightly overcast you may want to raise the camera's ISO setting a bit.
When you connect the camera to the helicopter make sure to mount it against something that will act as a shock absorber and reduce some of the high frequency the vibrations like a piece of rubber. If you rigidly mount the camera to your helicopter it will directly transfer the vibrations to the camera.
If you shoot video from your camera you should look into a video stabilizing plug-in like deshaker, or smoothcam, etc..
For a table of pre-computed CHDK shutter speed overrides check out my blog:
http://www.andrewhazelden.com/blog/2010/06/chdk-shutter-speed-overrides-explained/
