Which color illuminates in a switch to inform the crew that a system is available?

Which color illuminates in a switch to inform the crew that a system is available?

• A. Red
• B. Blue
• C. Amber
• D. Green

Answer: (D)

Status lights use color coding to convey status at a glance. Green on a switch shows the system is powered and available to use, i.e., operating normally. Red indicates a fault or dangerous condition, amber warns of degraded performance or need for attention, and blue is often used for advisory or special functions. Therefore, seeing green means the crew can rely on that system being ready, which is exactly what “system available” implies.

Status lights use color coding to convey status at a glance. Green on a switch shows the system is powered and available to use, i.e., operating normally. Red indicates a fault or dangerous condition, amber warns of degraded performance or need for attention, and blue is often used for advisory or special functions. Therefore, seeing green means the crew can rely on that system being ready, which is exactly what “system available” implies.