Electrical Flashcards by Heather Kelly

Describe the function of the GROUND SERVICE switch on the Forward F/A panel

Provides manual control of ground service busses. Enables servicing of airplane using external power without activating AC transfer busses

ON - connects external power to ground service bus

OFF - disconnects external power from ground service bus

VOL 2 / 6.1.5

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Explain the meaning of the blue GRD POWER AVAILABLE light

Illuminated blue - ground power is connected and meets airplane power quality standards

Note: doesn’t follow dim blue/bright blue logic. If it’s on - it’s available

VOL 2 / 6.1.4

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Explain the meaning of the blue APU GEN OFF BUS light

Illuminated blue - APU is running and not powering a bus (it’s available for use)

VOL 2 / 6.1.4

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Explain the meaning of the GEN OFF BUS

Illuminated blue - IDG is not supplying power to the related transfer bus

VOL 2 / 6.1.4

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Recall where to read voltage, frequency and amps

AC and DC metering panel on the forward overhead panel

VOL 2 / 6.1.2

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Explain the meaning of the amber DRIVE light

Illuminated (amber) - integrated drive generator (IDG) low oil pressure

VOL 2 / 6.1.3

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Explain the meaning of the amber TRANSFER BUS OFF light

Illuminated (amber) - Related transfer bus is NOT powered

Extinguished - Related transfer bus IS powered

VOL 2 / 6.1.4

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Explain the meaning of the amber SOURCE OFF light

Illuminated (amber) - No source has been manually selected to power the related transfer bus, or the manually selected course has been disconnected

Note: SOURCE OFF light triggers ELEC light and Master Caution to alert crew of change to source of power to associated Transfer Bus

VOL 2 / 6.1.4

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Explain the meaning of the amber BAT DISCHARGE light

Illuminated (amber) - with BAT switch ON, excessive battery discharge detected

VOL 2 / 6.1.2

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Explain the meaning of the amber TR UNIT light

Illuminated (amber) - TR failure

TR = Transformer Rectifier

VOL 2 / 6.1.2

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Explain the meaning of the amber ELEC light

Illuminated (amber) - fault exists in DC power system or standby power system

Note: operates only with airplane on the ground

VOL 2 / 6.1.2

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Explain the meaning of the amber STANDBY PWR OFF light

Illuminated (amber) - one or more of the following busses are unpowered:
- AC standby bus
- DC standby bus
- Battery bus

VOL 2 / 6.1.3

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Recall the number of minutes available on standby power with two fully charged batteries

60 minutes
VOL 2 / 6.2.5.2.2

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Recall the function of the Ground Power (GRD PWR) switch

Three position switch, spring loaded to neutral

OFF - disconnects ground power from AC transfer busses

ON - if momentarily moved to ON position and ground power is available:
- removes previously connected power from AC transfer busses
- connects ground power to AC transfer busses when power quality is correct

VOL 2 / 6.1.4

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Recall that it is not possible to use APU power and GRD power at the same time.

There are two basic principles of operation for the 737 electrical system:

No paralleling of AC sources of power
The source of power being connected to a transfer bus automatically disconnects the existing source

VOL 2 / 6.2.1.2

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Recall the function of positioning the APU Generator (GEN) switches to ON

Three position switch, spring loaded to neutral.

Neither AC transfer by powered by an IDG:
Moving an APU GEN switch to ON:
- Powers both AC transfer busses from the APU generator
- Disconnects external power, if connected
- Opposite SOURCE OFF light illuminates until the APU GEN switch is moved ON

Both AC transfer busses powered by IDGs:
Moving an APU GEN switch to ON:
- Powers the related AC transfer bus from the APU generator
- Other AC transfer bus continues to receive power from the IDG

VOL 2 / 6.1.4

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Recall the components powered by the ground service bus

Utility outlets
Cabin lighting
Battery chargers

Memory Aid:

CUB

VOL 2 / 6.2.2.4

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Recall the location of the GROUND SERVICE switch

The forward flight attendant control panel

VOL 2 / 6.1.5

Recall the function of the Generator (GEN) switches

Three position switch spring loaded to neutral

OFF - disconnects IDG from related AC transfer bus by opening generator circuit breaker

ON - Connects IDG to related AC transfer bus by disconnecting precious power source and closing generator circuit breaker

VOL 2 / 6.1.4

Recall the function of the BUS TRANSFER switch

AUTO (guarded position) - bus tie breakers operate automatically to maintain power to AC transfer busses from any operating generator or external power

OFF - isolates AC transfer bus 1 from AC transfer bus 2

VOL 2 / 6.1.4

Recall the function of the Generator Drive Disconnect (DISCONNECT) Switches (guarded)

Disconnects IDG if electrical power is available and engine start lever is in IDLE. IDG cannot be reconnected in the air

Note: It’s mechanically disconnected and has to be fixed by maintenance on the ground

VOL 2 / 6.1.3

Explain the function of the BAT (battery) switch

ON:
- provides battery power
- provides automatic switching of standby electrical system to battery power with loss of normal power

OFF:
- removes battery power

VOL 2 / 6.1.2

An illuminated SOURCE OFF light indicates:

Both A and B

No source has been manually selected to power the related transfer bus
the manually selected source has been disconnected

ESV-VA: ELECTRICAL

An illuminated STANDBY PWR OFF light indicates:

One or more of the above

An unpowered AC STBY BUS
An unpowered DC STBY BUS
An unpowered Battery Bus

ESV-VA: ELECTRICAL

True or False: An illuminated TRANSFER BUS OFF light indicates that the related transfer bus is not powered

TRUE ESV-VA: ELECTRICAL

True or False: If an IDG has been disconnected while airborne, it cannot be reconnected while airborne.

TRUE ESV-VA: ELECTRICAL

With the BAT switch on, which light indicates an excessive battery discharge is detected?

BAT DISCHARGE ESV-VA: ELECTRICAL

Is it possible to use APU power and GRD power at the same time?

FALSE ESV-VA: ELECTRICAL

To isolate AC transfer bus 1 from AC transfer bus 2, the BUS transfer switch must be in what position?

OFF - it isolates AC Bus 1 from AC Bus 2 ESV-VA: ELECTRICAL

The GROUND SERVICE switch is located on what panel?

the FORWARD flight attendant panel ESV-VA: ELECTRICAL

Selecting the battery switch to the OFF position provides automatic switching of standby electrical power to battery power with loss of normal power.

FALSE That only happens if the battery is ON ESV-VA: ELECTRICAL

The connection and quality of ground power can be verified by observing which light?

GRD POWER AVAILABLE light ESV-VA: ELECTRICAL

Select component(s) NOT powered by the ground service bus

AC transfer busses The components powered by the Ground Service Bus are CUB: - C: Cabin lighting - U: Utility outlets - B: Battery chargers ESV-VA: ELECTRICAL

What is the indication that the IDG is not supplying power to the related transfer bus?

the BLUE GEN OFF BUS light is ILLUMINATED The light does not flash. The light is not amber. The light is not extinguished. ESV-VA: ELECTRICAL

When an engine driven generator (GEN) switch is selected OFF, it...?

disconnects the IDG from related AC transfer bus. ESV-VA: ELECTRICAL

A generator (DRIVE) light illuminates (amber) for low oil pressure in the integrated drive generator (IDG) caused by which of the following conditions:

All of the above (because they all could cause low oil pressure): - IDG failure - Engine shutdown - IDG automatic disconnect due to high oil temperature - IDG disconnected through generator drive DISCONNECT switch - Low generator frequency condition (engine running) ESV-VA: ELECTRICAL

What is the function of the GROUND SERVICE switch? select all that apply

- manual control of ground service busses - enables servicing airplane using external power without activating AC transfer busses ESV-VA: ELECTRICAL

What light indicates an excessive battery discharge is detected?

BAT DISCHARGE ESV-VA: ELECTRICAL

With both AC transfer busses powered by the IDGs, moving an APU GEN switch on: select all that apply

- Powers the related AC transfer bus from the APU generator - Allows the opposite AC transfer bus to remain powered by the respective IDG ESV-VA: ELECTRICAL

On aircraft equipped with two batteries, two fully charged batteries have sufficient capacity to provide standby power for a minimum of 60 minutes.

TRUE ESV-VA: ELECTRICAL

What switch is used to connect external power to the AC transfer busses?

GRD PWR Switch Not the GROUND SERVICE SWITCH ESV-VA: ELECTRICAL

Illumination of an APU generator off (GEN OFF) light indicates that the APU...

is running and not powering a bus ESV-VA: ELECTRICAL