The standby-instrument lighting system has the function to supply the necessary light for the standby instruments installed in the flight compartment. The system lets the flight crew control the light intensity to see the instruments indications in all conditions of ambient lighting.

The standby-instrument lighting system is mainly controlled by one function of the integral lighting controller, of the lamp-dimmer power supply and of the COCKPIT LIGHTS control panel. Two outputs of the integral lighting controller are used to supply power to the standby-instrument lighting system. An output of the lamp-dimmer power supply is used to supply power to the standby-instrument lighting system. Three buttons on the COCKPIT LIGHTS control panel are used to control the lighting intensity of different components of the standby-instrument lighting system. The components that are controlled by the standby-instrument lighting system are the standby compass, the integrated standby instrument (ISI) and the clock.

The integral lighting controller receives electrical power from the L MAIN BUS. The controller supplies the electrical power and controls the light intensity of the control panels and instruments which are part of the panel-integral lighting system. It can control the light output of light-emitting diodes (LEDs) and incandescent lamps. The standby-instrument lighting system uses incandescent lamps.

The standby-instrument lighting system uses the lamp-dimmer power supply No. 1. It supplies bright or dim control to the flight compartment switch/lights. The flight crew sets the bright/dim function with the ANNUN - BRT/DIM rotary button on the COCKPIT LIGHTS control panel in the flight compartment.

The standby-instrument lighting system uses the pilot-side COCKPIT LIGHTS control panel. There are three rotary buttons (potentiometers) used for the standby-instrument lighting system on this control panel. The GSHLD/L SIDE rotary button controls the left side zone which includes the standby compass lighting. The PEDESTAL rotary button controls the pedestal zone which includes the main instrument panel where the clock and the ISI are installed.

The integral lighting controller receives 28 VDC electrical power from the L MAIN BUS. The lamp-dimmer power supply No. 1 receives 28 VDC electrical power from the L ESS BUS and the R MAIN BUS.

The System Operation description includes:

Lighting Controls

On the pilot COCKPIT LIGHTS control panel, the GSHLD/L SIDE and PEDESTAL rotary knobs send variable control voltages to the integral lighting controller. The controller decreases these voltages through internal circuits. The lighting is off when the rotary knob is at the most counterclockwise position (DIM). The lighting is at full intensity when the rotary knob is at the most clockwise position (BRT). Between these two positions, the rotary knobs give a continuous intensity adjustment (dim function).

The ANNUN rotary knob on the COCKPIT LIGHTS control panel sends the bright/dim (BRT/DIM) control voltages to the lamp dimmer power supply. One output of the power supply is sent to the ISI. The lighting is off when the rotary knob is at the most counterclockwise position (DIM). The lighting is at full intensity when the rotary knob is at the most clockwise position (BRT).

Power Distribution

The BRT/DIM rotary knobs on the COCKPIT LIGHTS control panel supply variable voltages to the controller and the power supply to change the lighting intensity. The controller decreases the voltages from the rotary knobs to the applicable variable output related to the integral lighting system. This is done through internal voltage limiters. The controller supplies 1.5 to 5 VDC regulated voltage to the incandescent lamps of the standby compass, the clock, and the ISI. Also, the ISI receives 28 VDC from the lamp dimmer power supply.

Standby Compass

The standby compass has a light unit for the compass dial and the lubber line on the surface of the bowl. The light bulb is a special nonmagnetic bulb. The light unit is powered by 5 VDC from the integral lighting controller.

The left side zone which includes the standby compass lighting receives 28 VDC power from the L MAIN BUS. If the L MAIN BUS is lost, the standby compass lighting automatically goes to the R ESS BUS. The lighting intensity is set at a fixed level and cannot be adjusted.

Integrated Standby Instrument (ISI)

On the front side, the ISI has a liquid crystal display (LCD) panel and a bezel.

The LCD lighting is supplied by a 28 VDC input voltage from the lamp dimmer power supply. The ISI LCD intensity is controlled by the ANNUN rotary knob of the COCKPIT LIGHTS control panel. The ISI has also the BRT and DIM pushbuttons to control the ISI LCD intensity.

The BRT pushbutton increases the lighting intensity, and the DIM pushbutton decreases the lighting intensity. If the 28 VDC input fails, the dimming control stays available through the BRT and DIM pushbuttons on the ISI.

The lighting intensity of the bezel and control knobs is controlled by the PEDESTAL rotary knob of the COCKPIT LIGHTS control panel. The 5 VDC lighting input is supplied by the panel integral lighting system.

Clock

The display lighting is supplied by the 5 VDC from the integral lighting system. The 5 VDC lighting input is an isolated circuit and has no connection to any other circuit in the unit. The clock uses the input to control the LCD lighting and the bezel integral lighting.

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The standby-instrument lighting system has interfaces with the systems/components that follow:

• Clock
• Lamp-Dimmer Power Supply
• Panel Integral Lighting
• Integrated Standby Instrument
• Standby Compass System

All the components used in the standby-instrument lighting system are contained in other systems as shown in the list.

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