B777 Electrical

Boeing 777 Electrics

Boeing 777 Electrics

1 / 15

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

True.

False.

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.

2 / 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.

True.

False.

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

3 / 15

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

Main battery.

APU.

DC busses.

Back up generators.

4 / 15

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

Approach (APP) mode is selected for autoland.

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

One engine shutdown.

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

5 / 15

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

Main AC busses.

DC busses.

Left transfer bus.

Hot battery bus.

6 / 15

What is the electrical configuration during autoland?

The left transfer bus isolates from the right main bus.

There is no change from normal.

The left transfer bus isolates from the right transfer bus.

The right transfer bus isolates from the right main AC bus.

7 / 15

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

APU generator - respective IDG - opposite IDG.

Respective IDG - APU generator - opposite IDG.

Opposite IDG - APU generator - respective IDG.

Respective backup generator - APU generator - opposite backup generator.

8 / 15

What provides DC power on the B777?

Transfer busses.

Transformer rectifier units.

DC generators.

Standby inverters.

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 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.

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.

10 / 15

Which one of the following is not true about the ram air turbine (RAT) generator?

The RAT cannot be manually deployed by pushing the RAM AIR TURBINE switch if any of the AC transfer busses powered.

The RAT can supply electrical and hydraulic power simultaneously.

The RAT generator provides standby power to the C1 and C2 TRUs.

The RAT is deployed automatically if both AC transfer busses lose power in flight.

11 / 15

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

Right main bus.

Ground service bus.

Standby bus.

Left main bus.

12 / 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.

The right engine generator powers both main busses.

External power continues to supply the right main bus.

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

13 / 15

Will the IDG disconnect automatically for high temperature?

yes

no

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.

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.

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

15 / 15

Does electric power has priority over hydraulic power from the RAT?

yes

no

Hydraulic has priority, and if electric is shed, only the CA instrument bus is powered through the main battery

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