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737 > Electrical > Flashcards

Electrical Flashcards

0
Q

How is the IDG driven?

A

By N2 powered drive transmission

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1
Q

Stats on 3 IDGs:

A

Each generator supplies 3 phase, 115 volt, 400 cycle Alternating Current (AC) power.

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2
Q

IDGs are cooled how?

A

Fan air & engine fuel flow

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3
Q

How can an IDG auto disconnect?

A

High oil temp

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4
Q

How do you manually disconnect an IDG?

A

Guarded switch on ovhd panel

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5
Q

Can you reconnect a disconnected IDG?

A

No, only on gnd by mx

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6
Q

What provides speed to APU IDG?

A

APU fuel control unit

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7
Q

Is there a direct control switch for DC power?

A

No

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8
Q

When normal DC pwr isn’t available, what supplies DC pwr?

A

Battery

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9
Q

What bus is connected to the battery when the battery switch is off?

A

Hot batt bus ( also connected to APU starter)

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10
Q

What busses are powered when the batt switch is on:

A

Hot batt bus, batt bus, sw’d hot batt bus

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11
Q

With batt switch on, when stby pwr switch is in auto, what else receives pwr?

A

DC stby bus and AC stby bus VIA the static inverter

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12
Q

What is the point of the GROUND SERVICE button?

A

Powering just gnd service buses instead of every bus when external pwr is connected/avail

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13
Q

Where is the gnd service button?

A

Fwd flt attendant panel

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14
Q

What busses does AC Trans bus 1 pwr?

A

AC gnd service bus 1, AC main bus 1, Galley bus C + D and AC stby bus

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15
Q

What busses does AC Trans bus 2 pwr?

A

AC gnd service bus 2, AC main bus 2 , galley bus A+B

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16
Q

What does the GND PWR AVAIL light mean?

A

This light indicates not only that the power is connected, but that the power is of good quality.

17
Q

How many APU GEN switches need to be in the on position to power both transfer buses?

A

Just 1, the BTBs will close and both transfer buses will be powered. However, a source off light on the opposite side will illuminate

18
Q

Do engine generators automatically come online?

A

No, they must be selected on by the respective switches

19
Q

What does a SOURCE OFF light mean?

A

The SOURCE OFF light illuminates when the respective Transfer Bus is powered through the Bus Tie System.

20
Q

Does the APU generator automatically come online?

A

No. It must be selected on

21
Q

If the AC system is powered by one eng gen, what loads get shed in what order?

A
  1. Galley pwr on Trans bus 2
  2. Galley pwr on Trans bus 1
  3. Main bus 1&2
22
Q

Inflight, if the aircraft is pwred by just the APU, what is shed?

A
  1. All galley buses shed

2. Main bus 1&2

23
Q

On the ground, if only powered by APU, which buses are pwred?

A

APU tries to pwr all buses

24
Q

Battery bus primary & alternate sources of pwr:

A

Normal: TR 3
Alternate: battery charger or battery

25
Q

The cross bus tie is normally:

A

Closed

26
Q

When does the cross bus tie normally open and why?

A

The normally closed Cross Bus Tie relay opens when the autoflight Approach mode captures the glideslope with the Flight Director or Autopilot in use.
This feature provides electrical isolation during an approach, so that a fault on one system will not affect another system.

27
Q

What does the STANDBY POWER OFF light mean?

A

The STANDBY PWR OFF light illuminates when the Standby AC Bus, the Standby DC Bus, or the Battery Bus is not powered.

28
Q

How does the bus transfer switch work?

A

The BUS TRANSFER Switch in the AUTO position allows the BTB’s to operate automatically to maintain power on the Transfer Buses from any available source of AC power.
In AUTO, the DC Cross Tie Relay is closed unless the glideslope is captured by the autopilot and/or the flight director.

29
Q

What happens when the bus transfer switch is in the off position?

A

The BUS TRANSFER Switch in the OFF position isolates Transfer Bus 1 from Transfer Bus 2 if one IDG is supplying power to both Transfer Buses.
In addition, the OFF position opens the DC Crosstie Relay.

30
Q

What does the TRANSFER BUS OFF light mean?

A

The TRANSFER BUS OFF light illuminates when the respective Transfer Bus is not powered.

31
Q

What does the GEN OFF BUS light mean?

A

The GEN OFF BUS light illuminates when the respective IDG is not powering the related Transfer Bus.
The engine Generator Switches apply power directly to the related Transfer Bus.

32
Q

Inflight or on the ground with loss of all AC power, the AUTO position of the STANDBY PWR SWITCH allows the:

A

AC Standby Bus to be powered by the Inverter - which is powered by the battery: and the DC Standby Bus is also powered by the battery.

33
Q

The OFF position of the Standby Power switch:

A

removes all power from the AC Standby Bus and the DC Standby Bus.

34
Q

The digital display to see electrical components outputs and status needs what to operate?

A

Batt bus pwr

35
Q

What does the BAT DISCHARGE light mean?

A

A BAT DISCHARGE light illuminates when excessive battery discharge is detected with the BAT switch ON. This light can illuminate during an APU start.

36
Q

What does TR UNIT light mean?

A

A TR UNIT light illuminates when any TR fails on the ground, or inflight it monitors TR1 as well as a combined failure of both TR2 and TR3.

37
Q

What does the ELEC light mean?

A

An ELEC light illuminates on the ground when a fault exists in the DC power system or Standby power system. This light is inhibited inflight.

38
Q

What does the DRIVE Light mean?

A

A DRIVE light indicates problems with the generator drive unit.

39
Q

When will the DRIVE light illuminate?

A

It illuminates upon IDG failure, engine shutdown, IDG automatic disconnect, or manual IDG disconnect.

40
Q

Describe the automatic online IDG feature:

A

The automatic IDG on-line feature allows the engine generators to automatically come on-line if takeoff is made with the APU powering the electrical systems. This is a one time operation for each flight and protects the aircraft from an inadvertent loss of electrical power.
The automatic engine generator on-line feature only operates once inflight if the on-line APU power fails or is turned OFF.

737 (15 decks)

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