B777 Electrical

Boeing 777 Electrics

Boeing 777 Electrics

1 / 15

What is the correct electrical panel configuration for normal flight?

BUS TIE switches in AUTO, BATTERY switch OFF, GENERATOR CONTROL switches ON.

BUS TIE switches in ISLN, BATTERY switch ON, GENERATOR CONTROL switches ON

BUS TIE switches in AUTO, BATTERY switch ON, GENERATOR CONTROL switches ON.

BUS TIE switches in AUTO, BATTERY switch ON, GENERATOR CONTROL switches OFF.

2 / 15

During autoland, the busses isolate to allow three independent sources to power the three autopilots.

False.

True.

The left IDG powers the left AC transfer bus, the left main DC bus, and the captain’s flight instrument bus The right IDG powers the battery bus and AC standby bus through the main battery charger The backup system powers the right AC transfer bus, the right DC bus, and the first officer’s flight instrument bus.

3 / 15

During autoland, the busses isolate to allow three independent sources to power the three autopilot. In this case which one of the following is the power source for the right AC transfer bus, the right DC bus, and the first officer's flight instrument bus?

Backup System

APY Generator

Right IDG

Left IDG

4 / 15

How many main AC power sources are required to maintain the entire plane AC electrical load?

5

2

1

4

5 / 15

When will the RAT auto-deploy?

Both transfer busses unpowered, both engines fail and C hydraulic system low

Both transfer busses unpowered, all three hydraulic systems low, and both engines fail.

Both transfer busses unpowered, and both engines fail.

Both transfer busses unpowered, all three hydraulic systems low, both engines fail and C hydraulic system low

6 / 15

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

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

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

The APU generator is electrically identical to the IDG generators.

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

7 / 15

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

DC busses.

Main AC busses.

Left transfer bus.

Hot battery bus.

8 / 15

Backup power is provided by one variable speed, variable frequency generator mounted on each engine. A frequency converter converts the generator frequency to a constant 400 Hz. Only one backup generator can power the converter at a time.

False.

True.

9 / 15

Which of the following is not a main AC electrical power source?

APU generator.

Transformer Rectifier Units (TRUs).

Left and right engine integrated drive generators (IDGs).

Primary and secondary external power.

10 / 15

What is the correct source order for powering left and right main busses in flight?

APU generator - respective IDG - opposite IDG.

Opposite IDG - APU generator - respective IDG.

Respective backup generator - APU generator - opposite backup generator.

Respective IDG - APU generator - opposite IDG.

11 / 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.

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

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.

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.

12 / 15

How can you power the ground handling bus before shutdown if no external power is available?

The bus is powered as long as the right main bus is powered.

Deploy the RAT.

Start the APU.

Select the ground handling bus ON.

13 / 15

Which bus powers the main battery charger and the APU battery charger?

Right main bus.

Standby bus.

Ground service bus.

Left main bus.

14 / 15

Which one of the following is not true about the flight control DC electrical system?

Primary power for the flight control DC electrical system comes from permanent magnet generators (PMGs) housed within each backup generator.

Each PSA also uses a dedicated battery to prevent power interruptions to the related flight control DC bus.

Variable frequency PMG AC power is the unique power source for the power supply assemblies (PSAs).

Variable frequency PMG AC power is used by individual power supply assemblies (PSAs) to provide DC power to the three flight control DC busses.

15 / 15

What automatic switching will occur if you start the APU with external power on the BUS TIE system?

The APU connects to the BUS TIE and replaces primary external power.

The APU connects to the BUS TIE swıtches and powers the maın bus.

The APU connects to the BUS TIE and replaces secondary external power on the left main bus.

The APU connects to the BUS TIE switches but does not power either main bus.

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