Under which conditions do the emergency exit lights illuminate?

• A. Deacceleration force exceeding two G's, loss of essential DC bus power, emergency light test switch is positioned to on
• B. Engine failure only
• C. Landing gear retraction only
• D. Cabin pressure loss only

Answer: (A)

Emergency exit lighting is designed to come on whenever the aircraft is in an emergency or its power system is compromised, so evacuees can find exits even in adverse conditions. The three triggers described cover the main ways this lighting is activated: a loss of essential DC power automatically switches to the emergency lighting so it remains lit when normal power fails; the emergency light test switch allows maintenance crews to verify the system by forcing the lights to illuminate; and a severe deceleration event (more than two G’s) ensures the exit paths remain visible during a crash or hard stop.

Engine failure, by itself, does not automatically cause the exit lights to illuminate unless it also results in loss of essential power or the test switch is used. The same goes for landing gear retraction or cabin pressure loss—they’re not direct triggers for emergency exit lighting, so they wouldn’t guarantee illumination on their own.