- Is it possible to set this model up so as to avoid the 'fish-eye' effect? I understand the benefits of such lenses but I'd still really like to avoid it
Yes. Set it to 1080 instead of 1080w and you use a relatively medium-angle setting which avoids the fish-eye effect (by essentially only using the center portion of the picture). Field of view is then 127 degrees vs. 170 for wide-angle.
- How can you determine the appropriate volume level on the aircraft intercom for recording? Is it simply trial and error?
- I'm guessing all I need to connect the camera to the intercom is a cable that allows the mic input to be connected in parallel to the headset/intercom audio output, there's no need for any kind of additional amplification or impedance right?
I have not tried this yet, but if anything you will need a resistor or something in the circuit, instead of an amplifier. I would expect a lot of trial and error to be needed though.
EDITED: This looks like it will do just fine:
Video Recorder Audio Adapter - Fixed Wing - MyPilotStore.com
Just remember to get an enclosure that allows access to the mic port. You can get those from GoPro direct, but I suggest you look at the other link for the enclosure that includes the ND filter. One of those has an opening for the various connectors on the left hand side. See also below.
- Are there any ND filters for this camera? Is it possible to rig one up yourself?
See the link I posted for a guy who sells GoPro housings with ND filters built-in.