B777 Electrical

Boeing 777 Electrics

Boeing 777 Electrics

1 / 15

What does the green EXTERNAL POWER AVAIL light indicate?

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

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

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

External power is disconnected from the airplane.

2 / 15

What is the correct electrical panel configuration for normal flight?

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

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

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

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

3 / 15

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

Main DC busses.

Backup generators.

Engine generators.

Ram Air Turbine.

4 / 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

5 / 15

If the RAT is unable to maintain RPM, the RAT generator electrical load is shed until RPM is satisfactory. Power for standby electrical loads is provided by the main battery during deployment of the RAT and when RAT generator loads are shed.

False.

True.

The RAT is deployed automatically if both AC transfer busses lose power in flight. The RAT can be manually deployed by pushing the RAM AIR TURBINE switch on the overhead panel.

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 primary power source for 'fly-by-wire'?

APU.

Battery.

Main AC busses.

Permanent magnet generators.

8 / 15

What is the electrical configuration during autoland?

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

The left transfer bus isolates from the right transfer bus.

There is no change from normal.

The left transfer bus isolates from the right main bus.

9 / 15

Bus tie relays, controlled by BUS TIE switches, isolate or parallel the right and left main busses. When both BUS TIE switches are set to AUTO, the bus tie system operates automatically to maintain power to both main busses.

False.

True.

10 / 15

What is the primary source of DC power during normal flight?

DC generators.

Transformer rectifier units.

APU battery.

Main battery.

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.

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.

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

12 / 15

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

The RAT can supply electrical and hydraulic power simultaneously.

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

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

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

13 / 15

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

4

7

5

6

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

14 / 15

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

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.

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

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

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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