B777 Electrical

Boeing 777 Electrics

Boeing 777 Electrics

1 / 15

What does the green EXTERNAL POWER AVAIL light indicate?

External power is connected to the airplane, correct and ready to power the electrical busses.

Electrical power is available to the electrical busses but may not be correct.

External power is disconnected from the airplane.

External power is connected to all the airplane's electrical busses.

2 / 15

What is the primary source of power for the transfer busses?

Engine generators.

Main DC busses.

Ram Air Turbine.

Backup generators.

3 / 15

The standby inverter converts DC power to AC power. The inverter powers the AC standby bus if the right transfer bus is not powered.

False.

True.

The standby inverter converts DC power to AC power. The inverter powers the AC standby bus if the left transfer bus is not powered.

4 / 15

What is the source of standby electrical power if the RAT sheds electrical power because of low hydraulic pressure?

Back up generators.

DC busses.

APU.

Main battery.

5 / 15

Which one of the following is not a reason for the backup electrical system to automatically power one or both transfer busses?

Only one main AC generator (includes APU) is available.

Power to one or both of the main AC busses is lost.

Approach (APP) mode is selected for autoland.

One engine shutdown.

6 / 15

Which one of the following is not true about the APU generator?

The APU generator is electrically identical to the IDG generators.

The APU generator cannot power both main busses at the same time.

In flight, when both transfer busses are unpowered, the APU starts automatically, regardless of APU selector position.

If no other power source is available when the APU generator becomes available, the APU generator automatically connects to both main AC busses.

7 / 15

What is the secondary source of power for 'fly-by-wire' if one or more PMGs are unpowered?

DC busses.

Left transfer bus.

Hot battery bus.

Main AC busses.

8 / 15

Primary power for the flight control DC electrical system comes from permanent magnet generators (PMGs) housed within each backup generator. Variable frequency PMG AC power is used by individual power supply assemblies (PSAs) to provide DC power to the three flight control DC busses. To ensure a high level of system reliability, each PSA also has multiple AC power sources.

True.

False.

To ensure a high level of system reliability, each PSA also has multiple DC power sources (No AC power!). If primary PMG AC power is not available, secondary power for the left and right PSAs is provided by the related main DC bus. Secondary power for the center PSA is provided by the captain’s flight instrument bus. The hot battery bus provides additional backup power for the left and center PSAs only. Each PSA also uses a dedicated battery to prevent power interruptions to the related flight control DC bus. The batteries have limited capacity and are incorporated to supply power for brief periods during PSA power source transfers.

9 / 15

Which one of the following is not true about the Primary External Power?

If both busses are powered from secondary external power, pushing the PRIMARY EXTERNAL POWER switch ON connects primary external power to the both main busses.

If a single IDG powers both busses, pushing the PRIMARY EXTERNAL POWER switch ON connects primary external power to both busses and removes the IDG source.

When the Primary power source voltage and frequency are within limits, the primary external power AVAIL (available) light illuminates.

If the APU generator is running, pushing the PRIMARY EXTERNAL POWER switch ON connects primary external power to the right main bus, leaving the previous source connected to the left main bus.

10 / 15

How many total AC sources of power does the B777 accommodate?

5

7

4

6

Seven (2 IDG, APU, PRI and SEC external power, 2 BUG).

11 / 15

Which items below are de-powered if you position the BATTERY switch to OFF during power down?

The APU battery and the hot battery bus.

The battery bus, Fırst Offıcer’s dısplay and the rıght AIMS.

The engine fire extinguisher bottles and APU fire extinguisher bottle.

The standby bus, Captain's displays and left AIMS.

12 / 15

Which one of the following is not true about the Secondary External Power?

If a single IDG powers both main busses, pushing the SECONDARY EXTERNAL POWER switch ON connects secondary external power to both busses and removes the IDG source.

If the BATTERY switch is ON and no other source is powering the main busses, pushing the SECONDARY EXTERNAL POWER switch ON connects secondary external power to both main busses.

When the secondary external power source voltage and frequency are within limits, the secondary external power AVAIL (available) light illuminates.

Secondary external power can only power the left main bus.

13 / 15

How are the busses powered if the right engine is started with the APU powering the left bus system and external power powering the right bus system?

The right engine genrator automatically powers the right main bus.

There is no automatic switching till the left engine is started.

External power continues to supply the right main bus.

The right engine generator powers both main busses.

14 / 15

The Electrical Load Management System (ELMS), manages load shed priority (galley first, utility bus second, then selected AC components).

False.

True.

15 / 15

You have a cold airplane (no power connected). Which items will be powered if you push the BATTERY switch ON?

Only the main battery bus will be powered.

The hot battery bus will be powered.

The APU controller and the DC fuel pump will be powered.

Your score is

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