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Chapter 5
Electrical

 5.1 Emergency configuration
 5.2 Battery only
 5.3 IDG low oil pressure/high temperature
 5.4 Generator fault
 5.5 Battery fault
 5.6 AC Bus 1 fault
 5.7 AC Bus 2 fault
 5.8 AC Ess Bus fault
 5.9 AC Essential Shed Bus lost
 5.10 DC Bus 1 fault
 5.11 DC Bus 2 fault
 5.12 DC Essential Bus fault
 5.13 DC Essential shed
 5.14 Loss of DC Bus 1 and DC Bus 2
 5.15 Generator overload
 5.16 Loss of TRs
 5.17 Battery bus fault
 5.18 DC Emergency configuration
 5.19 Static inverter fault
 5.20 Generator 1 line off
 5.21 Tripped circuit breakers

5.1 Emergency configuration

Attempt to restore normal power by recycling the main generators. If that fails, try again after splitting the systems with the bus tie button.

If normal power cannot be restored, ensure that the emergency generator is on line (deploy the rat manually if required) and maintain speed >140kt to avoid rat stall. Cycling fac1 will recover rudder trim. Once 45 seconds have elapsed and when below fl250, the apu can be started.

So much equipment is lost in the emergency configuration that qrh elec emer config sys remaining provides a table of surviving equipment. Notable losses are:

The qrh elec elec emer config summary should be applied once ecam actions are complete.

[ elec emer config, qrh aep.elec, fcom pro.aep.elec ]

5.2 Battery only

Battery power is available for approximately 30 mins.1

qrh elec emer config sys remaining provides details of remaining equipment. Mostly this is the same as for emergency electrical configuration (see Section 5.1). Notable additional losses are:

An attempt should be made to bring the emergency generator on line with the emer elec pwr man on button.

[ elec ess buses on bat, qrh aep.elec, fcom pro.aep.elec ]

5.3 IDG low oil pressure/high temperature

The idg should be disconnected. Assuming the associated engine is running, press the idg button until the gen fault light comes on. Do not press the button for more than 3 seconds.

The apu generator should be used if available.

[ elec idg 1(2) oil lo pr/ovht, fcom pro.aep.elec ]

5.4 Generator fault

Try to reset the generator by turning it off, then, after a short pause, turning it on again. If unsuccessful, turn it back off.

If an engine driven generator cannot be recovered, the apu generator should be used if available.

Single generator operation leads to shedding of the galley. Loss of an engine driven generator leads to loss of cat 3 dual capability.

[ elec(apu) gen (1)(2) fault, fcom pro.aep.elec ]

5.5 Battery fault

The affected battery contactor opens automatically. apu battery start is unavailable with a single battery.

[ elec bat 1(2) fault, fcom pro.aep.elec ]

5.6 AC Bus 1 fault

Some or all of the equipment on ac bus 1 becomes unavailable, including tr1: dc bus 1 is powered from dc bus 2 via the battery bus.

Power must be re-routed to the essential ac bus via ac bus 2. This is automatic on some aircraft. Manual re-routing is achieved with the ac ess feed button. Once essential ac is powered, the essential tr powers the dc essential bus.

Notable lost equipment includes the blue hydraulic system, ra1 (and hence cat 3 capability), half the fuel pumps, the nose wheel steering, the avionics blower fan and cm1 windshield heat.

[ elec ac bus 1 fault, fcom pro.aep.elec ]

5.7 AC Bus 2 fault

Some or all of the equipment on ac bus 2 becomes unavailable, including tr2: dc bus 2 is powered from dc bus 1 via the battery bus.

The majority of this equipment has a redundant backup, the loss of the fo’s pfd and nd and a downgrade to cat 1 being the major issues. Landing distances are unchanged.

[ elec ac bus 2 fault, fcom pro.aep.elec ]

5.8 AC Ess Bus fault

It may be possible to recover the bus by transferring its power source to ac bus 2 with the ac ess feed button. If this is unsuccessful, some or all of the equipment on the ac essential bus will be lost.

The majority of this equipment has a redundant backup, with the loss of the Captain’s pfd and nd and a downgrade to cat 1 being the major issues. Landing distances are unchanged.

It is worth noting that loss of ac essential bus implies loss of passenger oxygen masks. The mel allows dispatch without operative passenger oxygen masks provided that operating altitude is limited to 10,000ft. Where possible, a descent to this altitude would seem appropriate.

Where it is not possible to immediately descend to 10,000ft, a compromise level whereby a descent to a safe altitude can be achieved without masks needs to be chosen. The main form of guidance on altitude hypoxia comes in the form of “Time of useful consciousness” tables. Working on the principal that if you remain conscious you definitely remain alive, 25,000ft would seem to be a reasonable compromise. This gives you 2 to 3 minutes of useful consciousness to dive to 18,000ft, where you would then have 30 minutes to clear any terrain.2

[ elec ac ess bus fault, fcom pro.aep.elec ]

5.9 AC Essential Shed Bus lost

Some or all of the equipment on the ac ess shed bus is lost. The major issue is the loss of the passenger oxygen masks (see discussion in Section 5.8). Landing distances are unchanged.

[ elec ac ess bus shed, fcom pro.aep.elec ]

5.10 DC Bus 1 fault

Some or all of the equipment on dc bus 1 is lost. Most of the equipment loss causes loss of redundancy only. Landing distances are unchanged.

[ elec dc bus 1 fault, fcom pro.aep.elec ]

5.11 DC Bus 2 fault

Some or all of the equipment on dc bus 2 is lost. Notable items are:

The other lost systems either have redundant backups or are non-essential. It should, however, be noted that the only flight computers remaining are elac1, sec1 and fac1, so not much redundancy remains.

[ elec dc bus 2 fault, fcom pro.aep.elec ]

5.12 DC Essential Bus fault

The major headache associated with dc essential bus failure is a significant loss of redundancy in communications systems.

acp1 and acp2 are lost, along with vhf1. This allows two-way communication to be recovered by one pilot using acp3 (selected via the audio swtg rotary selector) with vhf2 or vhf3. Since speaker 1 is also lost, having cm2 handle the radios with speaker 2 at high volume is the only method of both pilots having awareness of atc communications.

On some airframes,3 this loss of communications is exacerbated by a design flaw: the audio cards for cockpit mikes and headsets are all powered from the dc essential bus. It may still be possible to receive transmissions with a combination of vhf2/3, acp3 on fo and speaker 2, but transmission is limited to morse code on the transmit switch.4

Other notable lost equipment includes:

[ elec dc ess bus fault, fcom pro.aep.elec ]

5.13 DC Essential shed

The only major issue is the loss of wing anti-ice. Therefore, avoid icing conditions, and apply landing distance procedure if ice accretes.

[ elec dc ess bus shed, fcom pro.aep.elec ]

5.14 Loss of DC Bus 1 and DC Bus 2

Some or all of the systems supplied by dc bus 1 and dc bus 2 are lost.

The implications are the same as for dc emergency configuration (see Section 5.18) except that the rat will not need to be deployed since ess tr will be supplied from ac bus 1 instead of the emergency generator.

[ elec dc bus 1+2 fault, fcom pro.aep.elec ]

5.15 Generator overload

Shed some load by switching off the galleys.

[ elec gen 1(2) overload, elec apu gen overload,
fcom pro.aep.elec ]

5.16 Loss of TRs

No systems are lost as a result of failure of a single tr. If the fault is with tr1 or tr2, dc ess will be supplied by the ess tr via the ac essential bus; in this case only cat 3 single will be available.

Dual failures involving the ess tr are similar to single failures, except redundancy is further compromised. If, however, both tr1 and tr2 fail then dc bus 1, dc bus 2 and the dc battery bus will be lost. The dc essential bus will remain powered by the ess tr.

The fcom is not very forthcoming regarding this failure; there is only a description in the dsc section and nothing specific in the pro section. The situation is, however, very similar to the “ecam complete” phase of dc emergency configuration (see Section 5.18), the only difference being that ac bus 1 rather than the emergency generator is providing the power to the ess tr, and hence you don’t need to worry about rat deployment.

[ elec tr 1(2), elec ess tr fault, fcom pro.aep.elec ]

5.17 Battery bus fault

Some or all of the equipment on the battery bus is lost. The only notable losses are apu fire detection and apu battery start.

[ elec dc bat bus fault, fcom pro.aep.elec ]

5.18 DC Emergency configuration

Defined as the loss of dc busses 1 and 2, the dc essential bus and the battery bus. Recovery assumes that the dc essential bus can be fully restored by deploying the rat with the emer elec pwr button.

Equipment powered or controlled through dc busses 1 and 2 and the battery bus is therefore lost.

Loss of the equipment associated with the battery bus is fairly benign: mainly apu battery start is unavailable due to loss of the apu ecb and apu fire detection.

A lot of equipment is lost with the loss of dc busses 1 and 2, but it is worth remembering that all three affected busses are also lost in emergency electrical config. Thus, you will have, at minimum, all the equipment listed in qrh elec emer config sys remaining. The main items of note are:

[ elec dc emer config, fcom pro.aep.elec ]

5.19 Static inverter fault

Normal operations are not affected.

[ elec stat inv fault, fcom pro.aep.elec ]

5.20 Generator 1 line off

Pressing the gen 1 line button on the emergency electrical panel has much the same effect as pressing the gen1 button on the main electrical panel, with the difference that gen1 continues to supply its associated fuel pumps. It is primarily used for the smoke drill. If it’s not meant to be off, turn it on.

[ elec emer gen 1 line off, fcom pro.aep.elec ]

5.21 Tripped circuit breakers

It is generally not recommended to reset circuit breakers in flight. It is, however, acceptable to attempt a single reset if it is judged necessary for the safe continuation of the flight.

On the ground, any circuit breakers other than those for the fuel pumps may be reset as long as the action is coordinated with moc.

An ecam warning will be triggered if a green circuit breaker trips. If the circuit breaker is left tripped, additional tripped circuit breakers on the same panel will not be detected.

[ c/b tripped, fcom pro.aep.elec ]

1This information was part of Airbus cbt training. There is no figure available in the fcom.

2These tables are obviously not designed to be used in this way – the exposure to hypoxia in the descent will likely impact the touc at 18,000ft, and we are really more concerned with survivability than useful consciousness – but they can at least give a feeling for the parameters involved.

3msns 2184–2402 and msns 2471–3122 at time of writing.

4I am only inferring this solution from the list of equipment lost; there is no specific documentation to indicate that it will work.

5easyJet aircraft automatically modulate to 1000psi, but the sim may not.