FCOM/FCTM: 24 - Electrical

Question 1

What are the ratings of the systems that normally power the aircraft?

Answer 1

AC system: three phase, 400Hz, 115V
DC system: 28V

06/06/2024

Question 2

What are the key speeds to remember when the RAT is supplying electrical power?

Question 3

In normal operations, what are the main sources of electrical power?

Answer 3

2 engine driven generators, producing 115VAC.
1 APU generator, also producing 115VAC.
Some of the AC is converted into DC by Transformer Rectifiers.

06/06/24

Question 4

What is the difference between deploying the RAT on the EMER ELEC PWR panel and HYD panel?

Question 5

What powers the AC ESS BUS?

Question 6

Can you re-engage a CB in flight that has tripped off by itself?

Question 7

What happens if you press & hold the IDG pbs for more than 3s?

Question 8

At what temp does the ELEC: IDG 1(2) OIL OVHT trigger?

Question 9

What are the main engine driven generators rated to supply?

Answer 9

90 kVA at 115V or 200V, at 400Hz

06/06/24

Question 10

How are the outputs of the engine driven generators regulated?

Answer 10

By the GCU (Generator Control Unit), which controls the line contactor.

06/06/24

Question 11

What is the rating of the APU generator?

Answer 11

The same as the engine driven generators:
90 kVA at 115V or 200V, at 400Hz

06/06/24

Question 12

What is the rating of the emergency generator?

Answer 12

5kVa, 3-phase, 115V & 200V, 400Hz

Question 13

When will the static inverter activate?

Answer 13

If only the batteries are supplying electrical power to the aircraft:
Speed >50kt: no matter if BAT pbs are on or off.
Speed <50kt: only if BAT pbs are on.

06/06/24

Question 14

What is the rating of the TRs?

Answer 14

28V 200A each
(TR1, TR2 and ESS TR)

06/06/24

Question 15

What are the batteries rated at?

Answer 15

23Ah

06/06/24

Question 16

What is the difference between green CBs and black CBs?

Answer 16

Green are monitored
Black are not
Monitored CBs will trigger a warning the ECAM warning “C/B TRIPPED” when they have tripped for more than 1 min.

06/06/24

Question 17

When clearing an ECAM “C/B TRIPPED”, what must you be aware of?

Answer 17

Using the CLR pb will clear the caution. If the C/B remains pulled, further tripped C/Bs on the same panel will not trigger further cautions. If the C/B is reset, then cautions will continue to be triggered.
The EMER CANC pb inhibits ALL “C/B TRIPPED” ECAM cautions.

06/06/24

Question 18

What happens if you lose both main generators in flight?

Answer 18

The RAT will extend automatically and starts powering the emergency generator. This whole process takes about 8 sec. In the transition period, the batteries power the emergency generation network.

06/06/24

Question 19

Above what speed will the RAT extend automatically, if needed?

Answer 19

100kt

06/06/24

Question 20

Discuss flying in EMER ELEC.

Answer 20

Only screens on the LHS are powered, so CM1 becomes PF.
AP, FD and ATHR are lost.
Flight is in alternate law (no protection), with direct law once gear selected down.
Only the EWD (upper ECAM) is available, so careful use of the ECAM control panel is needed.
Speed needs to be maintained above 140kt in order for the RAT to keep functioning.
RA 1+2 are lost, meaning no associated call-outs.
CAT 1 only.
QRH summary available.

06/06/24

Question 21

Which displays are available in EMER ELEC?

Answer 21

PFD1 and the EWD (upper ECAM)

06/06/24

Question 22

Explain the sources of electrical generation and their priorities.

Answer 22

GEN 1 and GEN 2 have highest priority.
Next is the APU, except if external power is available and the EXT PWR pbs is pushed ON.

06/06/24

Question 23

In flight under normal operations which generator has the higher load, and why?

Answer 23

GEN 1, because normally this will be supplying the AC ESS BUS (via AC BUS 1) and the DC ESS BUS and DC BAT BUS (via TR 1, which in turn is taken off AC BUS 1).

06/06/24

Question 24

What does the emergency generator power?

Answer 24

AC ESS BUS
DC ESS BUS (via ESS TR)

06/06/24

Question 25

Approximately how long does the emergency generator take to come online?

Answer 25

8 sec

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Question 26

While the emergency generator is starting, what is powering the aircraft?

Answer 26

After the loss of all AC power, the emergency generation network transfers to the batteries and the static inverter.

06/06/24

Question 27

What speed must be maintained for the RAT to function properly?

Answer 27

140kt

06/06/24

Question 28

What is the difference between selecting the GEN off and the IDG off?

Answer 28

GEN 1(2) pbs controls the line contactor, whereas the IDG pbs disconnects the IDG from its driveshaft and is not re-settable in flight.
This is why the IDG pbs is guarded.

06/06/24

Question 29

What is the purpose of selecting the APU master switch on the overhead panel in the smoke configuration checklist?

Answer 29

XXXXX

Question 30

Under what circumstances will the RAT extend automatically?

Answer 30

Loss of AC BUS 1 and AC BUS 2, with speed > 100kt.

06/06/24

Question 31

At what altitude can the APU be started in the EMER ELEC config, and why?

Answer 31

If in EMER ELEC config, the maximum altitude for APU start is 25,000ft.
Remember that above 25,000ft the APU may supply electrical power only (not bleed air AND electrical power).
Above this altitude, the air density is too low and a start on battery only (as is the case in EMER ELEC) may result in a failed start attempt.

06/06/24