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Mod 11 > 11.6 - Electrical Power > Flashcards

11.6 - Electrical Power Flashcards

1
Q

What happens when the disconnect solenoid is energised while the engine is stopped

A

The disconnect device is triggered and the clutch is damaged when the engine is started

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2
Q

How is a CSD disconnect reset performed

A

The reset ring is pulled when the engine is completely stopped

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3
Q

What is the function of the voltage regulator in the GCU

A

To control the voltage at the point of regulation 115V by influencing the ecciter current

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4
Q

Which is the voltage for an under voltage condition

A

100 volts

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5
Q

What happens with a generator working in isolated condition when it receives more exciter current than necessary

A

Voltage will increase

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6
Q

When does the differential protection circuit trip the generator

A

When the current in 1 phase differs

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7
Q

What happens when you exchange 2 phase connections at the generators terminals

A

The generator runs in reverse

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8
Q

How can you check the charge level of a ni-cad battery

A

You must measure the charge current, if it is nearly zero the battery is fully charged

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9
Q

What happens when a ni-cad battery overheats during charging

A

The charging current increases and could/would start a thermal runaway

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10
Q

Which of the following methods is used to charge a battery in an electrical power system

A

The batteries can be charged by a Transformer Rectifier Unit (TRU) using the constant voltage charging method

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11
Q

Consider a 2 engine aircraft with a isolated orientation of the main bus bar, what happens in the event of a failure of one of the main engine generators in flight

A

The remaining engine generator supplies the main AC bus bar on the failed side via the bus-tie breakers and the galley loads are shed

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12
Q

Consider a multi-engined aircraft (x4) with parallel generators. What happens if the number 2 bus-tie contactor is opened

A

Generator 1, 3 and 4 supply main bus bar 1, 3 and 4 in parallel and generator 2 powers main bus 2 seperatly

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13
Q

How is an open phase in a generator detected

A

By comparing the generator load in each phase

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14
Q

What does it mean when a Avail light in the external power push button illuminates

A

The external power source is activated to supply the network and the GND service must be switched to

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15
Q

How are the engine driven generators of multi engined aircraft (3 or 4 engines) usually operated

A

In parallel operation

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16
Q

How many resets are permitted after a circuit breaker has tripped

A

1, to prevent contacts from welding if a short has occurred

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17
Q

What does the abbreviation RCCB mean

A

Remote Control Circuit Breaker

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18
Q

Which is the principle of operation of the CSD disconnect

A

Electronically disconnected and mechanically reconnected

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19
Q

Which is the maximum permitted time for operating a CSD disconnect button

A

3 seconds

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20
Q

Which protective functions are built into the aircraft’s transformer rectifier (TR) units

A

Low current and high temperature protection

21
Q

Why are there 2 short pins in there external power receptacle

A

They ensure that the external power can only be applied if the plug is located correctly in the power receptacle

22
Q

How can the CSD disconnect be reliably confirmed

A

Zero volts and zero frequency is indicated

23
Q

Which are the main components of a static inverter

A

Solid state switches and a transformer

24
Q

What happens if the bus tie switching is set to off during operation with only ground power available

A

Te power to the main bus bar is lost

25
Q

What is the main advantage of parallel operation of the main AC busses over isolated operation

A

All engine driven generators are loaded equally and there is no power loss when one generator fails

26
Q

Why are trip free circuit breakers used on aircraft

A

Because they can open an overloaded circuit even with the control knob jammed in

27
Q

Which statement accurately describes the bus-tie switching operation in a Boeing multi engined aircraft

A

The bus-tie switching is normally closed. This is known as parallel operation

28
Q

Consider the function of a GCU. Which of the following statements are true

A

The GCU’sof the engine driven generators are identical and interchangeable

29
Q

How are the engine driven generators of a twin engine aircraft usually operated

A

In isolated operation

30
Q

What is the purpose of the 2 min delay before resetting a circuit breaker

A

To allow the bi-metallic strip in the circuit breaker to cool down

31
Q

Which statement is correct concerning the input speed of the generators producing a voltage with a frequency of 400Hz

A

The speed depends on the amount of pole pairs, 24000 RPM with one pole pair and 8000 RPM with three pole pairs

32
Q

How does the static inverter generate the correct output frequency

A

With a beat generator

33
Q

Which statement is correct concerning the functions of a circuit breaker

A

The CB trips when the normal current is exceeded for a certain time even if the control knob is pressed

34
Q

What is the Transformer Rectifier Unit (TRU) used to convert

A

3 phase 115V AC from the AC power distribution into 28V DC for the DC power distribution

35
Q

On a 3 phase generator what is the angle between phases

A

120deg

36
Q

What electrolyte solution is used in a Ni-Cd battery

A

A strong alkaline

37
Q

What is the voltage and frequency required to energise the aircraft electrical system

A

115V AC and 400Hz

38
Q

How is the aircraft normally electrically powered in flight

A

Engine driven generators

39
Q

What is the main source of power when the Aircraft is on the ground

A

External power

40
Q

How is the speed of the motor controlled in the CSD

A

Hydraulically

41
Q

Which are the main components of a static inverter

A

Solid state switches and a transformer

42
Q

What is the function of the GCU regulation circuits in generators that can work in parallel

A

To make sure that all generators share the same load when they are switched into parallel operation

43
Q

What is the function of the voltage regulator in the GCU

A

To control the voltage at the point of regulation to 115V by influencing the exciter current

44
Q

What is the main advantage of parallel operation of main AC buses over isolated operation

A

All engine driven generators are loaded equally and there is no power loss when one generator fails

45
Q

Which of the following power source can work in parallel operation

A

APU and external power

46
Q

Which statement accurately describes the bus tie switching operation in a Multi engine aircraft

A

The bus tie switching is normally closed. This is known as an isolated operation

47
Q

Which is the maximum current value that can be used in aircraft circuit breakers

A

125 amperes

48
Q

Which of these protection functions is used in TR units

A

Over temperature protection

49
Q

Which statement is correct concerning the function of a circuit breaker (CB)

A

A CB trips when the nominal current is exceeded for a certain time, even if the knob is pressed

Mod 11 (21 decks)

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