6. Electrical

What is the primary source of electrical power on the Boeing 737?

• Two engine integrated drive generators (IDGs)
• Auxiliary Power Unit (APU) generator
• External ground power
• Main battery

Answer explanation

The primary source of electrical power on the Boeing 737 is provided by two engine integrated drive generators (IDGs).

What type of current do the engine integrated drive generators (IDGs) supply?

• Single-phase, 115 volt, 60 cycle AC
• Three-phase, 115 volt, 400 cycle AC
• Three-phase, 230 volt, 50 cycle AC
• Single-phase, 230 volt, 60 cycle AC

Answer explanation

The engine integrated drive generators (IDGs) supply three-phase, 115 volt, 400 cycle alternating current.

What happens to an existing source of power when a new source is connected to a transfer bus on the Boeing 737?

• It remains connected
• It disconnects automatically
• It switches to a backup mode
• It shares the load with the new source

Answer explanation

The existing source of power disconnects automatically when a new source is connected to a transfer bus.

What are the three main divisions of the Boeing 737 electrical power system?

• AC power system, DC power system, and emergency power system
• AC power system, DC power system, and standby power system
• AC power system, emergency power system, and auxiliary power system
• DC power system, standby power system, and auxiliary power system

Answer explanation

The three main divisions of the Boeing 737 electrical power system are the AC power system, DC power system, and standby power system.

What maintains a constant generator speed in the engine IDGs?

• An integral hydraulic device
• An integral electro-mechanical disconnect device
• A variable frequency drive
• A mechanical speed regulator

Answer explanation

The engine IDGs maintain a constant generator speed through an integral electro-mechanical disconnect device.

What can the APU generator supply power to on the Boeing 737?

• Only the AC ground service busses
• Both AC transfer busses
• Only the DC power system
• Only the standby power system

Answer explanation

The APU generator can supply power to both AC transfer busses on the ground or in flight.

Where is the external AC power receptacle located on the Boeing 737?

• Near the tail
• On the upper fuselage
• Near the nose gear wheel well
• On the wings

Answer explanation

The external AC power receptacle is located near the nose gear wheel well, on the lower right side of the fuselage.

What is the function of the ground service switch on the forward attendant's panel?

• Provide power to all airplane electrical busses
• Provide ground power directly to the AC ground service busses for utility outlets, cabin lighting, and the battery charger
• Disconnect external power source
• Switch between AC and DC power sources

Answer explanation

The ground service switch provides ground power directly to the AC ground service busses for utility outlets, cabin lighting, and the battery charger.

How is DC power supplied on the Boeing 737?

• By the main battery and auxiliary battery only
• By the transformer rectifier (TR) units and the main battery/battery charger
• By the APU generator and external power
• By the engine IDGs only

Answer explanation

DC power is supplied by the transformer rectifier (TR) units and the main battery/battery charger.

What are the main and auxiliary batteries used for on the Boeing 737?

• Backup power for the AC and DC standby system
• Primary power for the DC power system
• Power for the APU generator
• Power for the external ground service

Answer explanation

The main and auxiliary batteries provide backup power for the AC and DC standby system.