How does a B-17 gunner swing a pair of .50 caliber machine guns through a full circle without shredding his own tail, wings, or propellers? The answer is a combination of mechanical engineering and early electrical logic built directly into the turrets. The core problem: - A powered turret like the Sperry upper turret can rotate a full 360 degrees - During that sweep, the gun barrels pass over the vertical stabilizer, the wings, and the propeller arcs - In combat, a gunner tracking a fighter is watching the target, not his own airframe - Even a brief burst into the tail could cripple the aircraft Solution 1: the fire interrupter - A cam or profile plate is machined to match the outline of the aircraft as seen from the turret - As the turret rotates and the guns elevate, a follower rides along that profile - When the barrels line up with a protected zone, the follower opens a switch in the firing circuit - The trigger solenoids lose power and the guns stop firing, even if the gunner ...