I have found the best results for sound are obtained by putting a "tie clip" microphone into the earpiece of my DCs.
Plugging direct into a spare headphone outlet had massively high levels of interference from the transponder (I think). Plus, when the mic is in your earpiece, the sound of the engine is attenuated nicely...
I use a "Fisheye lens" and it seems to capture the interior shots nicely, as well as letting the approach and landing shots turn out well.
Image stabilisation is a must.
In my experience, you tube videos must catch your attention in the first thirty seconds or they'll never get watched.