The Full Form of FCSA is‍ Fire Controlman Seaman Apprentice.

Fire controlmen provide system employment recommendations; perform organizational and intermediate maintenance on digital computer equipment, subsystems, and systems; operate and maintain combat and weapons direction systems, surface-to-air and surface-to-surface missile systems, and gun fire control systems at the organizational and intermediate level; inspect, test, align, and repair micro/minicomputers and associated peripheral equipment, data conversion units, data display equipment, data link terminal equipment, print devices, and system related equipment; make analysis for detailed systems, computer programs, electronics, and electronic casualty control; and operate associated built-in and external test equipment; load, initialize, and run preprogrammed diagnostic, performance and testing routines for digital computer equipment, digital subsystems, digital systems, and overall combat systems.

Fire controlmen attend apprentice technical training and “A”-School at Naval Station Great Lakes; this course is roughly 8 months long followed then by a “C”-school, based on one of the systems described below, which vary in length from 4 months to 8 months.

FCs typically operate weapon systems on-board surface combatant ships. They are trained in the repair, maintenance, operation and employment of weapons such as the Tomahawk missile system, the close-in weapons system, the 5″/54 caliber Mark 45 gun weapon system and its associated MK86 or MK160 gun fire control system, the MK92 gun fire control system (on frigates) the Sea Sparrow missile system, and the Harpoon missile systems. These include their associated computer and sensor packages. Their job is somewhat unusual in that they are trained to troubleshoot and repair their systems, as well as operate them. These responsibilities are typically split up between different ratings for various types of electronic equipment.

In essence, they operate the weapons sensors and tracking devices, from first detection through firing the weapons, to defend the ship against tactical threats or to make offensive strikes against hostile targets.

Another area of responsibility for FCs is the Aegis weapon system, which includes one of the most powerful air-search sea-based radars, the SPY-1, as well the MK99 fire control system, used for terminal guidance of Standard missiles, and the Aegis computer suite.