I could be wrong, but I think you need to purchase a timer remote (intervalometer). You can get a compatible timer like the Pixel TC-252 for $40 or so.
Yes, you need an external intervalometer controller. They are $20 if you look around.
GH2 on an R/C plane? Better to look at a GoPro camera. Smaller, lighter, tougher, and has a built in intervalometer.