A320 Electrical Questions

Which communication and navigation radios are operational in the Emergency Electrical Configuration with the EMER GEN powering the system?

• ACP 1 and 2, VHF 1, HF, RMP 1, VOR 1, and ILS 1.
• VHF 1, RMP 1, VOR 1.
• RMP #1 & #2, VHF #1, HF (if equipped), ACP #1, VOR #1 and ILS #1.
• All radios are lost.

Explanation: The QRH's "ELEC EMER CONFIG SYS REMAINING" table, for the EMER GEN RUNNING column, lists VHF 1, HF 1, RMP 1, and both ACPs as NORM, and VOR and MMR (the ILS/GPS receiver) as "N°1 only" — matching ACP 1&2, VHF 1, HF, RMP 1, VOR 1, and ILS 1 exactly.

Electrical Abnormal Procedures - ELEC EMER CONFIG SYS REMAINING

An AC ESS FEED switch located on the overhead panel shifts the power source for the AC ESS bus from:

• AC bus1 to AC bus 2
• AC bus 1 to AC Grnd/Flt bus
• AC bus 2 to AC bus 1

Explanation: In NORMAL, the AC ESS bus is fed from AC BUS 1. Selecting ALTN (or the automatic switching logic kicking in if AC BUS 1 is lost) shifts that feed to AC BUS 2.

Electrical - Controls & Indicators (AC ESS FEED)

How many times can you reset a circuit breaker?

• Once.
• Once, if authorized by the procedures.
• Twice.
• Twice, if authorized by the procedures.

Explanation: This reflects the general operating philosophy around circuit breakers as protective devices rather than switches — a reset is done once, and only when a procedure specifically authorizes it, not as a routine troubleshooting step. The extracted FCOM text doesn't state this as a single numbered rule verbatim, so treat the precise wording with some caution even though the underlying principle is standard.

Electrical - General / Description

If a TR fails:

• The other TR automatically replaces the faulty one and the ESS TR supplies the DC Ess Bus
• The static inverter replaces the faulty TR
• The DC Bus on the faulty side is lost
• The Emergency generator supplies DC power on the faulty side.

Explanation: The FCOM's TR-fault distribution table confirms this: if TR 1 fails, TR 2 automatically takes over supplying DC BUS 1 (in addition to its own DC BUS 2), while the ESS TR takes over the DC ESS BUS — the same pattern applies symmetrically if TR 2 fails instead.

Electrical - General / Description (Distribution Table)

While operating on Emergency Electrical Power with the landing gear lowered which of the following statements is correct?

• If the APU is not operating it should be started at this time.
• The APU will not start until the aircraft has come to a complete stop and all power has been removed for 15 seconds.
• On the ground at 100 knots, the DC BATTERY BUS automatically reconnects to the batteries allowing APU start.
• At 70 knots ESS AC is disconnected from the batteries.

Explanation: Below 100 kt, the DC BAT BUS automatically reconnects to the batteries, and on the ground with only the batteries powering the emergency network, APU start is only available once speed drops below that same 100 kt threshold.

Electrical - General / Description (emergency generation network)

Which flight control computer will be inoperative with gear extension while in the Emergency Electrical Configuration?

• FAC 1 and ELAC 1.
• SEC 1
• SEC 1 and ELAC 1
• FAC 1

Explanation:

If AC Bus 1 fails the AC ESS bus is supplied by:

• Emer Gen.
• The RAT
• Static Inverter
• AC Bus 2

Explanation: The FCOM confirms AC BUS 2 can supply the AC ESS BUS via the AC ESS feed contactor — so if AC BUS 1 is lost, the AC ESS bus transfers to being fed by AC BUS 2 instead.

Electrical - Controls & Indicators (AC ESS FEED)

Having started the APU, how can you get the APU generator to power the electrical system?

• The APU generator must be switch on.
• By pushing the EXT PWR pushbutton thus disconnecting the external power.
• By pushing the BUS TIE pushbutton.
• You are unable to as the APU power output is outside normal parameters.

Explanation: External power outranks the APU generator in the priority order, so even with the APU generator switched on, it won't actually connect while external power is still supplying — pushing the EXT PWR pushbutton to disconnect ground power is what lets the (lower-priority) APU generator take over.

Electrical - General / Description