A defensive arrangement must account for systems being unavailable. In the example, two weapons placed fore and aft each have an arc of roughly 270 degrees. If one fails, the other still covers much of the ship's sides. A pair mounted on opposite sides, each covering 180 degrees, leaves a sector without support when its weapon goes down. The surviving mount cannot cover that sector. Arrangements with three or four systems raise the same question: how much coverage remains after a failure? The value of additional weapons therefore depends on where their firing arcs overlap.
Notable Point · 1:20-2:27
Fore-and-aft weapon arcs after a system failure
Overlapping firing arcs let fore-and-aft mounts retain coverage after one fails; weapons on opposite sides can leave an unsupported sector.