Mcheli Controls Help

I found a B-29 Superfortress in a chest, but I can't figure out how to fly it. Nothing happens when I press W, and I can't access whatever inventory screen you add fuel in. The only info I can find says it's supposed to be the R key, but that's the one used to switch seats.
Does anyone know how to how to refuel it, or start it if it doesn't need fuel?
Any help would be greatly appreciated, thanks!