The function of the emergency lighting is to supply light for safe exit of the aircraft in an emergency.

The emergency lighting has external and internal emergency lights that come on automatically if the main electrical power is not available and the emergency lights are armed.

The passenger door emergency light supplies light to the external areas adjacent to the passenger door in an emergency. There is one light installed aft the passenger door at FS397.00. This light is attached to the aircraft structure with screws. The light receives 6 VDC from the related emergency lighting power supply. The light color is white.

There are two overwing emergency exit lights. These lights supply light to the external overwing area of the right fuselage in an emergency. The two lights are installed on the right side of the aircraft at FS462.00 and FS525.00 and are attached to the aircraft structure with screws. The lights receive 6 VDC from the related emergency lighting power supply. The light color is white.

Two emergency lighting power supplies provide electrical power to all components of the emergency lighting system in an emergency. The power supplies are installed in the center fuselage aft of FS360.00 and aft of FS501.00. Each power supply has a battery pack and a battery charger.

The batteries are nickel-cadmium type and are rechargeable. The batteries of the power supplies are automatically charged from the R MAIN BUS when necessary. The forward emergency lighting power supply supplies electrical power to the passenger door emergency light and one overwing emergency exit light (FS462.00). The aft power supply provides electrical power to the three emergency lights.

The emergency lighting system can be operated manually or automatically. In manual mode, the lights are set on with the EMER LTS switch positioned to ON. The emergency lighting system operates automatically if the EMER LTS switch is in the ARM position and electrical power from the R MAIN BUS is lost.

When the switch is set to ARM and electrical power is available from R MAIN BUS, the nickel-cadmium batteries of the power supply units are charged from the R MAIN BUS.

The R MAIN BUS supplies the emergency lighting power supplies with 28 VDC. If the EMER LTS switch on the LIGHTING control panel is set to ON, the power supplies provide 6 VDC to the emergency lighting system. If the EMER LTS switch is set to ARM and the R MAIN BUS becomes unserviceable, the power supplies provide the emergency lighting system with 6 VDC from the internal batteries.

EICAS messages will show when the EMER LTS switch is operated manually. When the EMER LTS switch is set to ON, the EMER LIGHTS ON message will be shown. When the EMER LTS switch is set to OFF, the EMER LIGHTS OFF message will be shown.

The EICAS messages that follow are related to the emergency lighting system: