How is the Emergency Lighting System activated in an aircraft?

The Emergency Lighting System in an aircraft is activated through the loss of normal aircraft power. This activation mechanism is critical because, in the event of an emergency, the aircraft may lose its primary power source, which could disable essential lighting and safety systems. The emergency lighting is designed to automatically activate so that crew and passengers can safely navigate the aircraft and reach exits during an emergency situation or evacuation.

When normal power is lost, the emergency lighting system relies on backup power sources, typically battery-powered, ensuring that sufficient illumination is provided along aisles, exits, and other vital areas. This automatic activation is crucial for maintaining safety and visibility, allowing for an effective response during critical situations.

Other options, such as a manual switch in the lavatory or passenger requests through a call button, do not provide the immediate and reliable response needed in an emergency. Also, while onboard sensors might serve various functions within the aircraft, they are not responsible for activating emergency lighting specifically related to power loss.