B777 Electrical

Boeing 777 Electrics

Boeing 777 Electrics

1 / 15

Which condition(s) cause the ELEC GEN DRIVE L EICAS message to display?

Generator drive oil pressure is low.

GENERATOR CONTROL switch selected to OFF.

Either A or B is correct

Generator drive oil temperature is high.

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

The main battery provides standby power to the following:

The hot battery bus, the captain’s flight instrument bus, and the standby inverter.

The hot battery bus, the battery bus, the captain’s flight instrument bus and the standby inverter.

The hot battery bus, the battery bus and the captain’s flight instrument bus.

The hot battery bus, the battery bus, the captain’s flight instrument bus, the left and center flight control PSAs, and the standby inverter.

4 / 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.

False.

True.

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.

5 / 15

What is the primary power source for 'fly-by-wire'?

Permanent magnet generators.

Main AC busses.

APU.

Battery.

6 / 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.

7 / 15

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

Opposite IDG - APU generator - respective IDG.

Respective backup generator - APU generator - opposite backup generator.

APU generator - respective IDG - opposite IDG.

Respective IDG - APU generator - opposite IDG.

8 / 15

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

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

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

The RAT can supply electrical and hydraulic power simultaneously.

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

9 / 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.

Start the APU.

Select the ground handling bus ON.

Deploy the RAT.

10 / 15

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

Standby bus.

Right main bus.

Left main bus.

Ground service bus.

11 / 15

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

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

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).

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

12 / 15

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

True.

False.

13 / 15

Will the IDG disconnect automatically for high temperature?

no

yes

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

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

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.

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

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).

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