Based on Weaverfish's B-17 with working Tail Gunner. I reworked it so that you can do the same but with the Turret on the back of the plane. All controls are the same as for the original except the rotation of the guns.

Controls:
AG1 - Flaps (VTOL)
AG3 - Auto Pilot
AG7 - Activate Turret (VTOL for vertical rotation, Trim for horizontal rotation)
AG8 - Enable / Disable pilot controls

Recommendation for use: Turn on AG1 and AG8 and set your plane on course, then turn both of them off and turn AG3 and AG7 on and switch to CAM1 to get into the Turret view.
Have fun! It's hard to shoot anything down since the gun cannot aim under the horizont line and AI fighters mostly attack from that line or below that but keep trying. :)