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United Airlines 777 Airplane Systems Study Guide v5.2 (9/26/2023) > Electrical > Flashcards

Electrical Flashcards

1
Q

What happens to the APU and RAT when both transfer busses are lost in flight?

A

The APU automatically starts and the RAT automatically deploys

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2
Q

What are the components of the standby electrical system?

A

The Main battery, Standby inverter, RAT generator, and the C1 and C2 TRUs.

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3
Q

What causes the IDG drive to automatically disconnect from the engine?

A

High generator drive temperature.

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4
Q

The engine airplane AC/DC electrical load is supplied by ______.

A

any two main AC power sources

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5
Q

Secondary external power can power the ______.

A

left and right main busses

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6
Q

What does the illumination of a generator DRIVE light indicate?

A

Low IDG oil pressure

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7
Q

The primary external AVAIL light illuminates when the ______.

A

primary power source voltage and frequency are within limits

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8
Q

The external AVAIL light means power is plugged in and ______.

A

voltage and frequencies are within limits but not yet selected/connected

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9
Q

The BACKUP GEN OFF Light illuminated indicates _______.

A

a backup generator failure, a circuit fault, or the switch is off

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10
Q

Pushing the IFE/PASS SEATS power switch to OFF removes power from what?

A

All inflight entertainment components.

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11
Q

Once one engine is started, with no other electrical source providing power and the BUS TIE switches are in AUTO, the ______ powers both main busses.

A

IDG

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12
Q

The primary power source for the flight control DC electrical system are the _______ backup generator PMGs.

A

left and right

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13
Q

If demand from the RAT exceeds capacity to provide hydraulic and electrical power, which has priority?

A

Hydraulic power - electrical load is shed until satisfactory RPM is satisfactory.

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14
Q

What does the main DC electrical system use to produce DC power?

A

TRUs

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15
Q

Several events can cause the backup AC electrical system to operate automatically, one of these events is when _____.

A

power to one or both main AC busses is lost

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16
Q

The ground service bus is normally powered by the right main bus. The ______ and ______ are alternate sources of power.

A

APU generator, primary external power

17
Q

When the GEN CTRL switches are ON, the generator breaker is armed to close automatically when generator power is ______.

A

available

18
Q

The main battery provides standby power to the ______.

A

hot battery bus, battery bus, and standby inverter

19
Q

When AC power is removed from the airplane with the BATTERY switch ON, the PA system remains powered ______.

A

in flight or on the ground

20
Q

The backup generator system automatically powers the right transfer bus when _____.

A

approach mode (APP) is selected

21
Q

The main battery charger, when powered, will power the ______.

A

hot battery bus

22
Q

The ______ normally supply power to the flight control DC electrical system.

A

PMGs

23
Q

What is the maximum altitude for APU start?

A

43,100 feet

24
Q

Each engine-mounted backup generator contains _____ permanent magnet generator(s)
(PMG).

A

2

25
Q

Inflight, when both BUS TIE switches are set to AUTO, the priority for powering the left and right main busses is the ______.

A

respective IDG, APU generator, opposite IDG

26
Q

The ______ powers the AC standby bus if the left transfer bus is not powered.

A

standby inverter

27
Q

Several items are powered by the ground handling bus, item(s) include the _____.

A

forward and aft cargo doors

28
Q

During power source transfers (such as switching from the APU generator to an engine generator) operating sources are momentarily paralleled to prevent power interruption _____.

A

on the ground

29
Q

While on the ground, normally the IDG can be electrically disconnected from the main busses by selecting an external electrical power source or ______

A

by selecting the GEN CTRL switch to OFF

30
Q

On the ground, power transfers are made without interruption, except when ______.

A

switching between primary and secondary external power sources

31
Q

Pushing the CABIN/UTILITY power switch to OFF removes power from the ______.

A

ground service bus

32
Q

If primary external power is powering one or both main busses, and then the APU is started, the APU automatically connects to _______ after reaching operating speed.

A

the left main bus

33
Q

Which of the following is NOT powered by the ground service bus?

A

Refueling panel

34
Q

If the electrical loads exceed power available (airplane or external), ELMS ______.

A

automatically sheds nonessential systems

35
Q

Can you turn the battery off in flight?

A

No, the switch is inhibited.

36
Q

How does the APU generator compare to the IDGs?

A

It is electrically identical to the IDGs.

37
Q

What does the main DC electrical system use to produce DC power?

A

TRUs

38
Q

If an IDG is manually disconnected in flight with the DRIVE DISC switch, can the pilots reconnect it?

A

No, maintenance action is required on the ground.

39
Q

Doug spent several hours creating this Brainscape class. How can I show my appreciation for using these flashcards?

A

Make a small donation to his favorite charity! You can use PayPal!
https://www.flyingsamaritansmotherlode.org/

United Airlines 777 Airplane Systems Study Guide v5.2 (9/26/2023) (14 decks)

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