Boeing B-17G Flying Fortress
Radio Operator's Room
Here's the view out of the Radio Operator Room's ceiling hatch looking toward the aft vertical stabilizer.
Prior to late-build B-17G models, B-17s included a single .50 cal machine gun manned by the radio operator. The gun was mounted on a roller mechanism in the ceiling at the radio room hatch. When not in use, the gun was rolled forward and locked in place. However, it was found that this gun position was the least effective on the aircraft, so it was eliminated during the late stages of the war when German fighter activity was lessened. That left B-17s with twelve .50 Cal. machine guns for defense. Less weight translated into greater bomb load or longer range.