CDS

Common Display System

The DUs provide flight and engine information to the pilots from the CDS.

The Upper Display Unit displays engine and fuel indications, as well as crew alert messages. The Lower Display Unit operates with the ability to switch between secondary engine parameters and hydraulic system information.

ADIRU

Air Data Inertial Reference Units.

Provides the following information to the instruments, engines, B737 Flight Controls, FMC, and all other systems requiring inertial and air data.:

• Position
• Speed
• Altitude
• Attitude

The system includes two IRUs (Left and Right) which contain internal gyros and accelerometers for position information.

Other components of the ADIRS include:

• 4 Air Data Modules
• 1 Inertial System Display Unit
• 1 Mode Select Unit

Two main pitot tubes and four static ports provide pressure information for for speed and altitude. Two Alpha Vanes provide AoA information, and a Total Air Temperature probe provides air temperature to the ADIRS system.

This information is sent to the flight displays by two DEUs.

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DEU

Display Electronic Unit

The DEUs are computers and distribute information from various aircraft sensors and systems. The data is converted to digital signals and sent to the displays.

During normal operation DEU 1 supplies information to:

• CA’s DUs
• upper DU

While DEU 2 provides information to:

• FO’s DUs
• lower DU

Should either DEU fail, the other DEU will automatically control the other side. It allows all displays to use a single DEU source. *Note that while operating on a single DEU, each pilot still receives information from independent sources and both ADIRUs..

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EFIS

Electronic Flight Instrument System

With the DISPLAYS CONTROL PANEL switch in the NORMAL position, the left EFIS Control panel operates the captain’s flight instruments, while the right EFIS Control Panel operates the FO’s instruments. Should a panel fail, all displays are controlled by the remaining EFIS Control Panel.

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CDS Faults

There are three messages that display when there is a fault in the CDS or DEU system:

Fault message	Interpretation	Conditions	Color
CDS FAULT	Non-dispatchable fault in the CDS system	Ground only prior to second engine start	AMBER
CDS MAINT	Dispatchable fault in CDS system	Ground only prior to second engine start	WHITE
DSPLY SOURCE	A DEU has failed after both engines started or airborne	After both engine starts	AMBER

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