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Hawk Tech > Electrical System > Flashcards

Electrical System Flashcards

1
Q

What is the main power source for the Hawk, and what is its rating?

A

The engine driven generator.

25kVA

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2
Q

What rating is the APU driven aux generator?

A

12kVA

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3
Q

What voltage does the DC system run at?

What voltage are the two DC batteries (each)?

A

28V

24V

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4
Q

State the voltage, phase and frequency of the main and aux generators.

A

200/115V
3 Phase
400Hz

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5
Q

How is the main generator cooled?

A

Oil cooled - it has its own oil system.

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6
Q

How is the aux generator cooled?

A

Air cooled.

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7
Q

Which busbar do the main and aux generators feed directly?

How are the other busbars powered?

A

The 200V 3-phase AC Maintained Busbar.

The AC offloadable busbar is powered directly from the AC maintained busbar.
The 26V Single Phase AC busbar is powered by the AC Maintained busbar via a 115/26V transformer.

The 28V Main DC Busbar is fed from the AC Maintained Busbar via the TRU.
The 28V ESB is fed from the 28V Main DC Busbar.
The No.1 and No.2 battery busbars are fed directly from their respective batteries.

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8
Q

Name the 7 busbars used in the electrical system.
3 AC
4 DC

A

AC:
200V Maintained
200V Offloadable
26V Single Phase

DC: 
28V Main Busbar
28V Essential Services Busbar
No.1 Battery Busbar
No. 2 Battery Busbar
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9
Q

What system prioritises the power supplies?

What is the order of priority?

A

Interlock system.

Main Gen.
External Power
Aux Gen.

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10
Q

What volts and amps does the DC system run on?

A

28V, 250A.

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11
Q

How is the TRU cooled?

A

Fan cooled.

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12
Q

What busbar is the DC Voltage dial connected to?

A

The 28V DC ESB.

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13
Q

What does the VSU control?

A

The Bus-Tie contactor.

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14
Q

When will the VSU de-energise the bus tie contactor? (4)

A

When the engine start switch is selected to START on the ground.

When the relight sequence is initiated in flight.

When the VSU senses the 28V DC Main busbar voltage fall below 25V for more than 1 second.

When a fault condition exists.

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15
Q

What does the DC caption mean?

Therefore, what is powering the 28V DC ESB?

A

The DC bus tie contactor is opened.

The batteries.

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16
Q

What will happen if the GCU takes the main generator offline in flight?

A

The APU (and therefore Aux Gen, if switch turned on) will start automatically.

The DC caption will show until it is online.

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17
Q

How long may it take for the APU to start?

A

Up to 34 seconds.

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18
Q

What is the minimum voltage the landing gear requires to operate?

Which busbar does it get this power from?

A

21V

The 28V ESB.

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19
Q

What NH does the main generator come online at during an engine relight with the throttle at IDLE?

A

45%NH

20
Q

What happens to the APU when the Main Generator comes back online following an engine relight?

A

APU will automatically shut down 10s after main generator comes online.

21
Q

What will be the most obvious immediate indicator that you have lost AC power?

A

MFDs will lose power.

22
Q

What is the minimum voltage for the batteries to be considered serviceable?

A

23V

23
Q

Which busbar powers the PDMC?

A

28V DC ESB

24
Q

Which busbar powers the SDMC?

A

The 28V DC Main Busbar
AND
The 26V Single Phase AC Busbar

25
Q

What effect will pushing the relight button in flight have on the main generator?

A

It will turn the main generator off.

26
Q

Which busbar(s) does the VSU monitor?

A

The 28V Main DC Busbar and the 28V Essential Services Busbar.

27
Q

You are running through the pre-strap in checks, and the external power plug has been connected, but the connection is isolated. What do you need to do to allow external power to be used.

A

The battery switches in the front cockpit must be set to off briefly to allow the external power connection to become un-isolated. External power will remain connected when you turn the batteries back on - it only needs a moment with them off.

28
Q

What happens to the external power supply once the main generator is running following an engine start?

A

It is automatically isolated from the aircraft busbars by the interlock system.

29
Q

What happens to the APU on T/O if you left it running after start?

A

It will turn off within 10 seconds of weight off wheels.

30
Q

What is the expected battery life following a double generator failure?

What does it assume?

Why is it given as a range?

A

5 - 16.2 minutes

Load shedding has happened.
Only one attempted APU start.
Batteries initially in a high state of charge (>80%)
Ambient bay temp around 0 degrees.
Taxi/ landing light only used during landing.

Due to “VSU dormant failure mode” - i.e. several different combinations of failures may result in different rates of battery depletion.

31
Q

What does setting the Batt 1 and 2 switches to ON actually do?

A

Connects them to the 28V DC ESB.

32
Q

What battery switch position is required for the batteries to be charged by the generator/ APU/ external power?

A

ON.

33
Q

What is the voltage range of the Red band on the voltmeter?

A

15 - 23V

34
Q

What is the voltage range of the Green band on the voltmeter?

A

26 - 29V

35
Q

Under what conditions is the DC Bus Tie de-energized?

A

A fault condition occurs.
During Engine start on the ground.
During an engine relight in flight.
The 28V DC Main Busbar voltage falls below 25V for more than 1 second.

36
Q

What will activate the inertia crash switches?

A

A longitudinal deceleration of about 3g.

37
Q

What actions are automatically carried out if the inertia crash switches are activated?

A 
Batteries disconnected from 28V ESB.
Gen and Aux Gen turned offline.
Data Transfer Unit erased.
CSMU recording stopped.
IFF Emergency Transmissions triggered.
38
Q

At what ESB voltage level does equipment start to drop out due to low voltage?

A

18V.

39
Q

Below what voltage is a battery considered U/S on start?

A

23V.

40
Q

What indications can you expect if the Main Generator fails in flight?

A

Gen caption and audio.
DC caption and audio.

Yaw caption and audio.
AP caption and audio.

MFDs go blank.
SDMC is lost (PDMC continues to work).
HUD symbology remains functioning (generated by PDMC).

41
Q

What voltage is required to lower the flap and landing gear?

A

21V.

42
Q

What button can you press to minimise lighting in each cockpit?

A

NVG.

43
Q

At what voltage does the aircraft automatically revert to BOS?

A

20V.

44
Q

What voltage does the HDFD work down to?

A

18V.

45
Q

What are the “Big 4” when it comes to load shedding?

A

Probe heaters.
Datalink.
PDMC.
Landing Light.

Hawk Tech (16 decks)

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