B777 Electrical

Boeing 777 Electrics

Boeing 777 Electrics

1 / 15

On ground no power connected to the airplane. Which items will be powered if you push the BATTERY switch ON?

All statements are correct.

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

The hot battery bus will be powered.

Only the main battery bus will be powered.

2 / 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.

3 / 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.

One engine shutdown.

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

Approach (APP) mode is selected for autoland.

4 / 15

What is the electrical configuration during autoland?

There is no change from normal.

The left transfer bus isolates from the right main bus.

The left transfer bus isolates from the right transfer bus.

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

5 / 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.

True.

False.

6 / 15

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

Opposite IDG - APU generator - respective IDG.

APU generator - respective IDG - opposite IDG.

Respective backup generator - APU generator - opposite backup generator.

Respective IDG - APU generator - opposite IDG.

7 / 15

What provides DC power on the B777?

Transformer rectifier units.

Transfer busses.

Standby inverters.

DC generators.

8 / 15

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

Transformer rectifier units.

DC generators.

APU battery.

Main battery.

9 / 15

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

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.

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.

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 generator provides standby power to the C1 and C2 TRUs.

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

The RAT can supply electrical and hydraulic power simultaneously.

11 / 15

Which one of the following is not true about the backup electrical system?

A frequency converter converts the generator frequency to a constant 400 Hz.

If both IDGs and the APU generator are inoperative, a backup generator powers essential airplane equipment to reduce electrical loading on the backup generator, some of the systems becomes inoperative such as TCAS, Centre tank override/jettison pumps (centre tank fuel is unusable).

Right and Left backup generators power the converter at the same time.

Backup power is provided by one variable speed, variable frequency generator mounted on each engine.

12 / 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 switches but does not power either main bus.

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.

13 / 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.

14 / 15

Which one of the following is not true about Electrical Load Management System (ELMS)?

When an additional power source becomes available or the loads decrease, ELMS restores power to shed systems in the same order of shedding(First shed system restored first).

Priority for shedding is galleys first, then utility busses. Utility busses are followed by individual equipment items powered by the main AC busses.

The ELMS provides load management and protection to ensure power is available to critical and essential equipment.

If the electrical loads exceed the power available (airplane or external), ELMS automatically sheds AC loads by priority until the loads are within the capacity of the airplane or ground power generators.

15 / 15

The standby electrical system consists of:

The main battery and the RAT generator.

The main battery, the standby inverter, the RAT generator and its associated generator control unit and the C1 and C2 TRUs.

The main battery, the standby inverter, the RAT generator and the C1 and C2 TRUs.

The main battery, the standby inverter, and the RAT generator.

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