ELEC Control Panels

The whole crew interface to the electrical network fits on three panels: the overhead ELEC panel (235VU), the overhead EMER ELEC PWR panel (211VU), and the external power panel by the nosewheel — with one more switch, the ground-service / MAINT bus selector, on the forward attendant panel. Every other article in this chapter dives a single component; this one is the map. It walks the panels switch by switch, gives the verbatim FCOM legend for each, and points every cell at the component article that owns the mechanism behind it.

A consolidation article adds nothing the deep-dives do not already establish — its value is in reading the panel as one object. The detailed logic of each control was built up in the earlier articles (IDG, GCU, batteries, and so on); here the loop closes. By the end you should be able to answer five things a panel scan really tests:

1. The thirteen controls on 235VU — how they group, and the "dangerous position" of each.
2. Which controls carry a guard, and what the guard is warning about.
3. Which FAULT legends are inhibited, so that a dark legend cannot always be trusted (and a lit one is not always a protection trip).
4. The four controls on 211VU — their order of use on the approach, and the price each one charges.
5. What each OFF / reset cycle actually resets — because four different cycles reset four different boxes.

Per FCOM DSC-24-20.

1. The 235VU layout — three functional groups

FCOM lays the controls out by physical position; read by function they fall into three groups — a battery group that reads and manages the batteries, a generation group that excites, disconnects or ties the AC sources, and an external/load group that brings power in, sheds it, or re-routes it.

235VU  ELEC PANEL (overhead) — three functional groups
┌─ BATTERY GROUP ──────┬─ GENERATION GROUP ──────┬─ EXTERNAL / LOAD GROUP ─┐
│ BAT 1/2/APU selector │ IDG 1   IDG 2  ◄guarded │ EXT A        EXT B      │
│  + voltage display   │ GEN 1   GEN 2           │ GALLEY       COMMERCIAL │
│ BAT 1     BAT 2      │ APU GEN BUS TIE         │ AC ESS FEED  ◄guarded   │
│ APU BAT              │                         │                         │
└──────────────────────┴─────────────────────────┴─────────────────────────┘
  read & manage           excite / disconnect /      bring in / shed /
  the batteries           tie the AC sources         re-route the loads

Two guarded controls live on 235VU — IDG 1/2 and AC ESS FEED. The physical row-by-row placement is per the FCOM panel figure (p.1713); the grouping above is by job, which is how a pilot actually reasons about the panel.

2. The ELEC panel (235VU) — thirteen controls

2.1 Battery group

BAT selector + voltage indication. A three-position selector (1 / 2 / APU) drives a single voltmeter:

"BAT 1(2 or APU) selector: Selects the battery for voltage indication."

The display reads the selected battery's voltage and is available in any configuration, because it is fed off the permanently-powered hot-bus side — which makes it the master instrument when the aeroplane is otherwise dark (the indication logic on the ECAM DC page is detailed in Monitoring and Indication).

BAT 1 / BAT 2 pb (AUTO / OFF). The pushbutton commands the Battery Charge Limiter (BCL), not the battery directly. In AUTO the BCL opens and closes the battery line contactor on its own schedule:

"The batteries are connected to the DC BAT BUS in the following cases: Battery voltage below 26.5 V (battery charge). The charging cycle ends when battery charge current goes below 4 A (for 10 s on ground, 15 min in flight); On the ground (with speed below 50 kt), when batteries only are supplying the aircraft; In flight DC generation lost (limited to 7 s)."

Selecting OFF stands the BCL down — but it does not kill survival power:

"OFF : The Battery Charge Limiter is not operating, the DC ESS BUS is not connected to the battery (except in flight in emergency configuration). OFF comes on white if the DC BAT BUS is powered. Hot buses remain supplied."

Read that last clause carefully. OFF cannot disconnect the hot buses, and it cannot block the in-flight emergency-configuration DC ESS connection — management authority is not the same as survival authority. The FAULT legend is the thermal-runaway tell:

"FAULT lt : Comes on amber associated with an ECAM caution, when the charging current for corresponding battery is outside limits. In this case the battery contactor opens."

There are two distinct "reset" stories on this button, and the panel chapter only describes one of them. The reset it does describe is the ground-parking automatic cut-off:

"Automatic battery contactors open when: The aircraft is on the ground; The main power supply (external power plus all generators) is cut off; The battery voltage is lower than 23 V for more than 16 s. The flight crew can reset the contactors by switching the BAT pb-sw to OFF then to AUTO."

So the OFF→AUTO action here re-arms the parking cut-off contactors. The other reset — whether a thermal-runaway FAULT may be cleared and re-tried — is BCL family logic, and is handled in Batteries and the BCL, not on the panel.

APU BAT pb (AUTO / OFF). Identical to BAT 1/2 plus one extra connection trigger:

"AUTO : The APU Battery Charge Limiter automatically controls the closure/opening of the line APU BAT contactor. The battery is connected in the following cases: To ensure battery charge (as for BAT 1 or 2); When the APU start sequence is initiated."

Its automatic cut-off uses a longer confirmation window than the main batteries: AMM 24-38-00 gives the main batteries a ground cut-off when voltage is below 23 V for 16 s, and the APU battery a cut-off when its voltage is below 23 V for more than 60 s — the APU battery is given more rope so an APU start attempt is not cut short.

2.2 Generation group

IDG 1 / 2 pb (guarded). The only one-way control on the panel. Spring-loaded out, guarded, and protected by a hard time limit:

"CAUTION 1. If the pushbutton is pressed for more than about 3 s , damage may occur to the disconnection mechanism. 2. IDG disconnection is inhibited when the engine is stopped or below idle."

"IDG switches are normally spring loaded out. Pressing this switch disconnects the IDG from its drive shaft. Only maintenance personnel can reconnect it."

"FAULT lt : Comes on amber associated with an ECAM caution in case of: IDG oil outlet overheat (above 185 °C), or IDG oil pressure low. Inhibited when the engine is stopped or below idle. It goes off when the IDG is disconnected."

Three red lines belong to this button and are worked through in Integrated Drive Generator: pressing for more than about 3 s damages the disconnect mechanism; the underspeed inhibit is a hardware gate (the button does nothing on a stopped engine); and disconnection is an in-flight one-way ticket that starts a 50-hour replacement clock. Note also the inhibit cuts both ways — the FAULT legend is suppressed below idle, so a dark legend after shutdown is not evidence the fault has cleared.

GEN 1 / 2 pb (ON / OFF·R). Excite-and-tie, or de-excite-and-reset:

"On : The generator field is energized and the line contactor closes, provided electrical parameters are normal."

"OFF/R : The generator field is de-energized and the line contactor opens. The associated Generator Control Unit (GCU) is reset."

"FAULT lt : Comes on amber associated with an ECAM caution in the event of protection trip initiated by the associated Generator Control Unit (GCU). The line contactor opens."

The decisive footnote on what a reset can and cannot recover is verbatim here:

"Note: If the protection trip is initiated by a differential fault, the reset action has no effect after two attempts."

A differential trip is the one kind the reset will not clear after two tries — the GCU has decided the source is unsafe to bring back. The on-line acceptance gate itself is GCU hardware: AMM 24-22-00 closes the generator only once the PMG frequency is above 1260 Hz and the input speed is above 4900 RPM (the GCR and PRR thresholds), the detail of which lives in GCU and AC Generation Control.

APU GEN pb (ON / OFF·R). The APU generator's button mirrors the engine GEN button, but its ON legend carries one extra automatic action that is specific to the APU generator (not the engine GEN button):

"On : The APU generator field is energized and the line contactor closes provided parameters are normal. Each bus tie contactor 1 and (or) 2 automatically closes if its associated generator is not operative."

"FAULT lt : Same as GEN FAULT. APU GEN FAULT light is inhibited when APU speed is too low."

So bringing the APU generator on automatically closes whichever bus-tie contactor is needed to back up a dead engine generator. Its FAULT legend is inhibited at low APU speed; and note that the hard APU-oil protection (the ECB shutting the APU on its own thresholds) is upstream of this button entirely — see APU Generator and the GAPCU.

BUS TIE pb (AUTO / OFF). One button commands all three tie contactors:

"AUTO : The three BUS TIE contactors open or close automatically according to the priority logic in order to maintain power supply to all AC buses. The three contactors close when: only one engine generator supplies the aircraft, or only the APU generator or single ground power unit supplies the aircraft."

"OFF : The three BUS TIE contactors open."

The AUTO closing condition is exactly the case where one source must feed the whole network. Selecting OFF therefore means manually closing the only relief corridor to the other side — the priority arbitration behind it is in Network Priority and Normal Supply.

2.3 External power and load group

EXT A pb. A momentary button that toggles the right-half external source straight on:

"AVAIL lt : Illuminates green provided external power parameters are normal."

"Momentarily pressed : If the AVAIL light was on: The external power line contactor closes; The AVAIL light goes off; The ON light comes on blue. If the ON light was illuminated: The external power line contactor opens; The ON light goes off; The AVAIL light comes on."

One press connects; ON comes on blue. If a protection condition blocks the contactor, ON simply refuses to light.

EXT B pb. Same green AVAIL, but a different second state — a request, not a connection:

"Momentarily pressed : If the AVAIL light was on: Provided the APU generator is off the external power line contactor closes; The AVAIL light goes off; The AUTO light comes on. If the AUTO light was on: The external power line contactor opens; The AUTO light goes off; The AVAIL light comes on."

"Note: When external power B is selected AUTO, AUTO light remains illuminated even when the APU generator has taken over."

The asymmetry is deliberate; its root is priority, set out verbatim in the panel note:

"The APU generator has priority over external power (A and B) for AC BUS 1. The external power A has priority over the APU generator for AC BUS 2. The APU generator has priority over external power B for AC BUS 2. The engine generators have priority over the external power or APU. The external power B has priority over external power A for AC BUS 1."

Because EXT B's home is the left half (AC BUS 1), where the APU generator outranks it, EXT B can only request — and its AUTO legend stays lit even after the APU generator has taken the bus, which is not the same as EXT B supplying it. Both external sources are dived in External Power.

GALLEY pb (AUTO / OFF). The galley shed switch:

"AUTO : The galleys are normally supplied. The ECMU automatically controls the shedding of one or more galleys in case of generator(s) failure or in case of overload detection. On ground when APU generator or the external power supplies, all galleys are supplied provided no overload is detected."

"OFF : All galleys are shed. Water/Waste (drain mast) ice protection is lost. The electrical supply of the heating floor panels is shed."

"FAULT lt : Comes on amber associated with an ECAM caution in case of overload detection if the automatic shedding is not performed."

"Note: Switching OFF then AUTO resets the galleys which have been automatically shed by the ECMU."

Note the collateral of OFF — it takes the drain-mast ice protection and the heating floor panels with it, not just the galleys. Selecting OFF then AUTO is a conditional retry: it re-supplies the galleys the ECMU had shed, but if the overload is still present they are shed again at once. Mechanically the OFF action opens the ECMU galley relays 2XA1 and 2XA2 and through them all the galley RCCBs (AMM 24-26-00); the management logic is in ECMU and Contactor Management and Galley and Commercial Loads.

COMMERCIAL pb (ON / OFF). A bigger hammer than GALLEY:

"OFF : The following equipment is shed: Galleys; Cargo loading system; Electrical service; Escape slide lock mechanism ice protection; Water/waste (drain mast) ice protection; Lavatory and cabin lights; Water heater; In-seat power supply; Passenger entertainment system."

COMMERCIAL OFF reaches a whole ring wider than GALLEY OFF — the entire commercial sub-network plus all galleys — while the essential and flight equipment feel nothing. The bus structure is in AC Distribution and Busbars.

AC ESS FEED pb (guarded, NORM / ALTN). The re-routing of the essential family:

"Normal : The AC ESS BUS is supplied from AC BUS 1. It is automatically supplied by the AC BUS 2 when the AC BUS 1 is lost."

"ALTN : The AC ESS BUS is supplied from AC BUS 2."

"FAULT lt : Comes on amber associated with an ECAM caution when the AC ESS BUS is not electrically supplied."

The FAULT semantics are the trap: the legend means "the AC ESS BUS itself has no power", not "AC BUS 1 has no power". If AC BUS 1 is healthy but a feeder/contactor fault has left AC ESS dark, the automatic transfer does not act and the crew select ALTN by hand — the case worked in AC ESS Feed and Transfer. One ultimate fall-back is stated right on the panel:

"Note: In case of total loss of main generators the AC ESS BUS is automatically supplied by the emergency generator or by the static inverter if the emergency generator is not available."

3. The EMER ELEC PWR panel (211VU) — the four-piece set

211VU  EMER ELEC PWR PANEL (overhead) — four controls
┌─────────────────┬──────────────────────────────────────────────────────┐
│ MAN ON ◄guarded │ hand-start the CSM/G when the auto logic has not       │
│ EMER GEN FAULT  │ red: emergency gen not supplying & AC lost in flight   │
│ TEST  ◄guarded  │ press-and-hold ground check of the emergency chain     │
│ LAND RECOVERY   │ restore the AC/DC LAND RECOVERY buses for the approach │
└─────────────────┴──────────────────────────────────────────────────────┘

MAN ON pb (guarded). The manual fall-back when the automatic start has not fired:

"AUTO : In case of normal AC supply loss in flight, the emergency generator is automatically started."

"Pressed: The emergency generator runs and is connected to the aircraft network."

It is also the way to bring the emergency generator back in the RAT scenario, where slat extension sheds the CSM/G to dedicate the RAT to the flight controls — see Emergency Generator (CSM/G).

EMER GEN FAULT light (annunciator 14XE). Red, with a precise meaning:

"The light comes on red, if the emergency generator is not supplying and normal AC supply is lost in flight."

The teaching point sits in the timing: the CSM/G has a start sequence of up to ten seconds — AMM 24-24-00 fixes it at "the start-up sequence, 10 seconds maximum" — so a brief red illumination during that start window is normal, not a failure (the start-power detail is in Batteries and the BCL and the emergency-generator article).

TEST pb (guarded, press and hold). The ground functional check:

"Pressed and held : The emergency generator runs (provided the green hydraulic system is pressurized) and supplies the DC ESS BUS and the AC ESS BUS."

The precondition is verbatim — green hydraulic pressure must be available (from an electric pump or a ground source). The slats-extended inhibit and the rest of the test envelope are in the emergency-generator article.

LAND RECOVERY pb (ON). The approach restoration, with a list of exactly what comes back and what it costs:

"ON When pressed, with the emergency generator running, the AC LAND RECOVERY and the DC LAND RECOVERY buses are recovered and the following equipment are restored: LGCIU 1; SFCC 1 (flap channel is not recovered, if the emergency generator is powered by the RAT); BSCU channel 1 (not recovered, if the emergency generator is powered by the RAT); LH windshield anti-ice (not recovered, if the emergency generator is powered by the RAT); LH landing light (not recovered, if the emergency generator is powered by the RAT). The remaining fuel pump (if any) is lost."

"Note: The remaining fuel pump will be shed at 260 kt, if the emergency generator is powered by the RAT, or at LAND RECOVERY selection, whichever occurs first."

"When the LAND RECOVERY pb-sw is pressed in EMER ELEC configuration, ADR 3 is lost, and consequently, AP 1 is lost."

So the button buys back LGCIU 1, SFCC 1, BSCU channel 1, the LH windshield anti-ice and the LH landing light (these last four only when the EDP, not the RAT, is driving), on the AC/DC LAND RECOVERY buses (the DC land-recovery buses 407PP / 805PP per AMM 24-24-00). The deposit is steep: ADR 3 is lost, and with it AP 1, and the remaining fuel pump goes. Per FCTM PR-AEP-ELEC the button "should be pressed prior to commencing the approach" — i.e. before slat extension — which is why it appears as an APPR PROC item on the STATUS page. Full handling in Emergency Generator (CSM/G) and AC ESS Feed and Transfer.

4. The external power panel and the ground-service bus

Two indications live on the panel by the nosewheel connector — note the AVAIL light here is amber, a different lamp from the green AVAIL legend on the overhead EXT A/B buttons:

"EXT PWR A (B) Avail: This amber light comes on to indicate that external power is available and the voltage is correct."

"EXT PWR A (B) not in Use: This white light comes on to inform the ground personnel that the ground power unit is not supplying the aircraft network and can be disconnected. It goes off if EXT A (B) is in use."

The amber AVAIL tells the ground crew the GPU is good (and the cockpit may now select the overhead button); the white NOT IN USE tells them the plug is safe to pull.

One switch on the forward attendant panel rounds out the interface — the ground-service / MAINT bus selector:

"This switch allows maintenance and ground service personnel to energize electrical circuits for ground servicing, without energizing the aircraft's entire electrical system."

"ON : The selector latches magnetically, provided the external power A parameters are normal (AVAIL light is on). … The switch trips, when the external source is removed."

It is a magnetically latched switch feeding a small ground-servicing network without bringing up the whole aeroplane; when the external source goes away the latch drops and it springs back. The full small-network logic is in Ground Service and Maintenance Bus.

5. Reading the panels as a system

5.1 Four "OFF / reset" actions, four different boxes

The single most useful thing this panel map teaches is that the word "cycle it" means four different things on four different controls.

5.2 Five FAULT legends and their inhibit rules

A FAULT legend is only as trustworthy as its inhibit logic — three of these can be dark while the fault is live, and one is routinely lit without being a protection trip.

5.3 The deliberate asymmetry of EXT A and EXT B

EXT A  (home = right half / AC BUS 2)        EXT B  (home = left half / AC BUS 1)
─────────────────────────────────────        ───────────────────────────────────
   AVAIL (green) ──press──► ON (blue)            AVAIL (green) ──press──► AUTO
        ▲                     │                       ▲                    │
        └────────press────────┘                       └───────press────────┘
   one press = CONNECT                            press = a REQUEST only:
   (line contactor closes)                        closes ONLY if APU GEN is off;
                                                  AUTO stays lit even after the
                                                  APU generator has taken over

EXT A's home bus (AC BUS 2) is one where external power A outranks the APU generator, so a press connects outright. EXT B's home bus (AC BUS 1) is one where the APU generator outranks it, so a press can only register a request — and the AUTO legend persists after the APU generator takes the bus. Same priority table, opposite behaviour.

5.4 The language of the guards

Five guards across the two overhead panels — IDG 1/2 and AC ESS FEED on 235VU, and MAN ON and TEST on 211VU (plus, where fitted, the EMER GEN guard) — all say the same sentence: this action is either irreversible, or it changes ownership of a survival resource. The guard is a forced one-second pause to think. The IDG guard fronts a one-way ticket; the AC ESS FEED guard fronts a change of household for the essential family.

5.5 The 211VU four-piece in approach order

The four controls are used in a fixed order on the way down: confirm EMER GEN is on line (the red legend is out) → take the APPR PROC prompt on the STATUS page → press LAND RECOVERY before slat extension to recover SFCC 1 and the other landing equipment, accepting the loss of ADR 3 and AP 1 → and, if the RAT scenario sheds the CSM/G at slat extension, use MAN ON to bring it back when needed.

Self-test

[!note]- Q1. On 235VU, what does each "OFF / cycle" actually reset?

Four cycles, four boxes. GEN pb OFF/R de-excites, opens the GLC and resets the GCU protection (a differential trip will not clear after two attempts). BAT pb OFF→AUTO re-arms the ground-parking automatic cut-off contactors (the ones opened by 23 V for 16 s on the ground). GALLEY pb OFF→AUTO re-supplies the galleys the ECMU had shed, but conditionally — they shed again immediately if the overload persists. AC ESS FEED to ALTN is not a reset at all but a manual re-route to AC BUS 2, with no automatic switch-back in flight once AC BUS 1 recovers.

[!note]- Q2. Which FAULT legends are inhibited or carry a special window?

IDG FAULT is inhibited with the engine stopped or below idle, so a dark legend after shutdown is not proof the fault is gone (it also extinguishes once the IDG is disconnected). APU GEN FAULT is inhibited when APU speed is too low. GEN FAULT comes on for any GCU protection trip, so a lit legend is not necessarily a differential trip. The EMER GEN red legend may be on briefly during the ≤ 10 s emergency-generator start sequence and that is normal. AC ESS FEED FAULT means the AC ESS BUS itself is unpowered — not that AC BUS 1 is unpowered.

[!note]- Q3. Why do the two external-power buttons behave differently?

EXT A momentarily pressed connects outright — ON comes on blue. EXT B momentarily pressed only registers a request — AUTO — which closes the contactor only if the APU generator is off, and the AUTO legend stays lit even after the APU generator has taken over (so AUTO ≠ supplying). The root is the priority table: EXT B's home is AC BUS 1, where the APU generator outranks it; EXT A's home is AC BUS 2, where external power A outranks the APU generator.

[!note]- Q4. In what order are the 211VU four controls used on the approach, and at what cost?

First confirm the EMER GEN is on line (red legend out); take the APPR PROC STATUS-page prompt; then press LAND RECOVERY before slat extension to recover LGCIU 1, SFCC 1, BSCU channel 1, LH windshield anti-ice and LH landing light (the last four only with the EDP driving), at the cost of ADR 3 and therefore AP 1, plus the remaining fuel pump. If the RAT scenario sheds the CSM/G at slat extension, use MAN ON to bring the emergency generator back when needed.

[!note]- Q5. Which controls are guarded, and what is the common message of the guard?

On 235VU: IDG 1/2 and AC ESS FEED. On 211VU: MAN ON and TEST (plus the EMER GEN guard where fitted). The common message: the action is either irreversible (the IDG disconnect) or it changes the ownership of a survival resource (re-sourcing the ESS family, hand-driving the emergency generator). The guard exists to force a one-second pause before either.

Key takeaways

References

Per FCOM DSC-24-20 (the Controls and Indicators panel chapter, p.1713–1722: the BAT 1/2 and APU BAT pb connection cases, OFF and FAULT legends and the OFF→AUTO parking-cut-off reset; the IDG, GEN, APU GEN and BUS TIE pb legends including the 3 s caution, the differential-trip note and the APU-GEN bus-tie auto-close; the EXT A/B momentary-press logic and the external-power priority note; the GALLEY, COMMERCIAL and AC ESS FEED pb legends; the EMER ELEC PWR four controls — MAN ON, EMER GEN FAULT, TEST, LAND RECOVERY — and the external power panel AVAIL/NOT IN USE lights and the forward-cabin ground-service switch); AMM 24-38-00 (the 16 s main / 60 s APU ground deep-discharge cut-off windows); AMM 24-22-00 (the 1260 Hz / 4900 RPM generator on-line thresholds); AMM 24-24-00 (the 14XE EMER ELEC PWR/EMER GEN annunciator on 211VU, the LAND RECOVERY buses, and the 10 s maximum emergency-generator start sequence); AMM 24-26-00 (the 2XA1/2XA2 galley relays opened by GALLEY OFF); FCTM PR-AEP-ELEC (LAND RECOVERY pressed prior to commencing the approach). Component mechanism is carried by the deep-dive articles cross-referenced in each cell; this article restates panel legends and adds no new system facts of its own.

Independent study material, not an Airbus publication. Refer to current operator FCOM, FCTM, and QRH for operational use.