Emergency Electrical Configuration

The total loss of AC BUS 1 + 2. The hardware of the emergency generator, the "ECMU standby" logic of ECMU contactor management and the godfather lineage of AC ESS feed transfer all converge here into one procedure: ELEC EMER CONFIG (a red WARNING, LAND ASAP). It is the heaviest failure article in the chapter. It is built in four layers: the two procedural branches → the FCTM philosophy → the EDP / RAT two-state scripts → the restoration clause. The FCTM positions it first: this is a complex procedure — once the ECAM is complete you go to the QRH summary (16.01A) and the SYS REMAINING table (16.02A).

1. Trigger and the two branches

The trigger condition, in the procedure's own words: the main generators and all AC busbars are not supplied. The FWS offers two procedures, sorted by whether anything has since recovered.

Branch 1 — at least one source is back

GEN 1 and/or GEN 2 recovered, or APU GEN available: LAND ASAP → EMER ELEC PWR ... MAN ON (shown only if not already auto-coupled) → ALL GEN ... OFF THEN ON. This is the procedural face of the emergency generator's "the coupling does not yield" rule:

"When the emergency generator is automatically or manually coupled, and if at least one generator is recovered, the DC and AC ESS buses are still supplied by EMER GEN. The ELEC EMER CONFIG procedure is no longer displayed but replaced on the ECAM by the following procedure and status."

Per FCOM PRO-ABN-ELEC. Once the EMER GEN is coupled, the DC/AC ESS buses stay on it even after a generator recovers; the ELEC EMER CONFIG procedure is no longer displayed and is replaced by the follow-on procedure and status. A related procedure rides along: FUEL FCMC 1+2 FAULT (the dual-FCMC restart that follows the power interruption — see ATA 28).

Branch 2 — not recovered, APU unavailable

The main event. Read step by step:

LAND ASAP
EMER ELEC PWR ....... MAN ON      ← backstop after auto-start failed (the 3 s / 10 s window)
ALL GEN ............. OFF THEN ON ← first reset round (a GCU reset chance)
BUS TIE ............. OFF         ← "split the two generation corridors"
ALL GEN ............. OFF THEN ON ← second reset round

Why BUS TIE OFF is sandwiched between the two reset rounds (an integrative reading, cross-validated against the FCTM cause analysis): the FCTM says most EMER CONFIGs are rooted in a network anomaly such as a short circuit that trips every generator. If the short is on the corridor / busbar side, the first reset round simply re-feeds the fault and trips again. Setting BUS TIE OFF physically severs the left and right corridors before the second reset — a healthy-side generator can then survive on its own isolated half-network. This is a textbook fault-isolation move.

[!warning]- BUS TIE held OFF means the APU GEN cannot join the network

The STATUS spells it out: "Only in the case of GEN or ENG failure … set the BUS TIE to AUTO." So if you want to recover on the APU GEN you must first set BUS TIE back to AUTO — the island isolation that locked out the faulty side also locks out the APU GEN, which reaches the network through the BUS TIE corridor. "BUS TIE OFF island isolation" and "start the APU to restore power" are a knot to be untied: before trying the APU, BUS TIE → AUTO.

The follow-on procedure then forks by which source drives the EMER GEN. Comms: the EDP script is VHF 1 / HF 1 / ATC 1 (SELCAL inoperative); the RAT script offers VHF 1 only. Common items: VENT EXTRACT ... OVRD; if the standby airspeed disagrees with the captain's PFD, discard the standby (the standby probe is not necessarily on the de-ice list); engine anti-ice forced ON regardless of the pushbutton → fuel burn about +1.5 %; on the RR fit ENG 1+2 N1 DEGRADED + N1 MODE ON + MAN THR; SEC 2 KEEP ON; SPD BRK DO NOT USE. And:

"WEIGHT/CG INITIALIZE — This line appears because the FCMCs lose the WEIGHT/CG information, due to the power interruption that occurs before EMER GEN activation. The GW and CG must be initialized again in the FCMC, by manually re-entering their values in the FUEL PRED page."

Per FCOM PRO-ABN-ELEC. (A cost item on the emergency generator's timeline: those ten seconds of dead bus wiped the FCMCs' memory.) Single-side fuel feed plus the L/R PUMP 2 see-saw is the same picture as DC bus 1+2. The STATUS carries three hard limits at the top: MAX FL 350 / MAX SPEED 330/M0.82 / ALTN LAW: PROT LOST.

2. The approach sequence — the procedure and its cost

FOR SLATS EXTENSION:
  RAT MAN ............ ON         ← extend the RAT by hand first!
  LAND RECOVERY ...... ON         ← redeem the landing kit
  FOR LDG ............ FLAP LVR 3
FOR L/G GRVTY EXTN:
  MAX SPEED .......... 200 KT
  L/G GRVTY EXTN ..... DOWN        ← gravity gear (no retract on go-around + degraded climb)
WHEN L/G DN:
  MAN PITCH TRIM ..... USE         ← gear down = direct law, autotrim gone
LDG DIST PROC ........ APPLY

Why extend the RAT first even in the EDP script? The FCTM gives the reason:

"When the emergency generator is powered by EDP, this avoids strong fluctuation of the green hydraulic pressure which may cause a spurious disconnection of the emergency generator."

Per FCTM PR-AEP-ELEC. Slat actuation is a heavy customer of the green system — the pressure dip at the moment of slat extension can drive the CSM/G's speed governing unstable and trip its protection (the OS/UF picture from the emergency generator). Extend the RAT first to hold a reserve of green pressure, then extend the slats. The procedural LAND RECOVERY restores: ILS 1 (on the no-MMR fit) / SFCC 1 / LGCIU 1 / BSCU 1 / WHC 1; the cost is the same as ever (remaining fuel pumps lost / ADR 3 → AP 1 — see the emergency generator).

[!warning]- Nose-wheel steering is lost in all cases — directional control is rudder + differential braking

The FCTM body states NWS is lost in all cases: "the PF must use the rudder" — landing-roll directional control is rudder plus differential braking only, and the crew should set the A/SKID & N/W STRG switch to OFF. Several items in the big INOP list are not broken out in the FCTM two-state table yet are landing-critical: N/W STRG / AUTO BRK (autobrake lost); and the RAT script has no anti-skid on the pedals to begin with — prefer a dry, long runway, brake by hand, smoothly and in pulses. Two more costs after LAND RECOVERY: about 2 t of fuel per side is trapped in the inner tanks because the remaining pumps stop (L/R INR TK: 2T UNUSABLE), the approach guidance degrades to FLS: F-APP + RAW ONLY, and the FMS fuel prediction is untrustworthy ("Disregard FMS fuel predictions" — recompute per the QRH fuel penalty).

3. The FCTM four blocks — philosophy and the two scripts

Background — two cause families. The network-anomaly (short-circuit) type: every generator trips, the EDP drives the EMER GEN, and APU recovery is unlikely (the short is still on the network). The combined-failure (electrical + engine) type: recovery via the APU may be possible. The RAT-driven scenario is lower probability still — and crucially the QRH summary does not cover the RAT scenario (keep that boundary in mind when you use it). A mechanism worth knowing: above 260 kt the EMER GEN power rises with the engine windmill effect (the other face of the 3.5 kVA from the emergency generator — there is credit above 260 kt).

General guidance (every line is examinable): only PFD 1 → the left seat becomes PF; MAYDAY; LAND ASAP does not mean rushing toward a poor airfield in poor weather — the EMER GEN's drive source (EDP / RAT) should feed the airport decision; not recommended to hold this configuration for long; workload rises sharply; only the E/WD is available → ECP discipline; consider starting the APU; read the STATUS carefully; transfer to the QRH summary once the ECAM is complete; press LAND RECOVERY early, before the approach, do not delay.

The remaining-systems two-state table (the FCTM table, in the "fly, navigate, communicate" frame):

The restoration clause — the most-missed line:

"the LAND RECOVERY AC and DC BUS bars are initially shed and will remain shed until the LAND RECOVERY pb is set to ON. This remains true if normal electrical configuration is restored."

Per FCTM PR-AEP-ELEC. Getting the network back does not automatically return those segments — on any approach that has been through EMER CONFIG, press LAND RECOVERY, whether or not normal power has since come back.

4. Scenarios

1. Cruise EMER CONFIG (short-circuit type): left seat takes control (PFD 1) and calls MAYDAY; run the ECAM down branch 2 — two reset rounds around BUS TIE OFF; try the APU anyway (only the combined type has a chance, but trying costs nothing — remember BUS TIE → AUTO first); once the ECAM is done transfer to QRH 16.01A / 16.02A; weight the "EDP vs RAT" question into the airport decision.
2. Approach prep (EDP script): memorise the order — RAT MAN ON → LAND RECOVERY ON → slats → CONF 3 → gravity gear (200 kt) → manual pitch trim after gear down. Each step is irreversible (RAT out cannot retract / gear out cannot retract) — pace it early rather than late.
3. RAT script short final: the EMER GEN drops off the instant the slats extend and the screens shrink once more (landing on batteries) — expect it, do not be startled; keep correcting roll by hand (the right outer aileron floats up); no anti-skid on the pedals — prefer a dry, long runway.
4. GEN 1 revives mid-stream: switch to branch 1 — the ESS stays on the EMER GEN (it does not yield); still press LAND RECOVERY on the approach (the restoration clause); do not forget to re-enter GW/CG in the FCMC.

Self-test

[!note]- Q1. Where does BUS TIE OFF sit, and what is its purpose?

Sandwiched between the two ALL GEN OFF THEN ON rounds — in a short-circuit cause, it isolates the left and right corridors before the reset so a healthy-side generator can survive on its own island half-network (a fault-isolation move). Note the corollary: to recover on the APU GEN you must first set BUS TIE back to AUTO.

[!note]- Q2. Why RAT MAN ON before the slats?

In the EDP script, slat actuation causes strong green-pressure fluctuation that can spuriously disconnect the EMER GEN — extending the RAT first holds a green-pressure reserve. In the RAT script it is the drive source anyway. The step is unified across both scripts.

[!note]- Q3. The three-row difference between the two scripts?

FLY: EDP has both trims, RAT is all manual + the right outer aileron floats up (roll out of trim). NAV: EDP has ND 1 / FMGC 1 / radar, RAT has none. COM: EDP is VHF 1 + HF 1, RAT is VHF 1 only. On approach the RAT script loses the EMER GEN when the slats extend and lands on batteries, with no anti-skid.

[!note]- Q4. Why initialise WEIGHT/CG?

The power interruption before EMER GEN activation wipes the GW/CG from both FCMCs — re-enter them by hand on the FUEL PRED page. The same interruption brings the FUEL FCMC 1+2 FAULT related procedure.

[!note]- Q5. The restoration clause?

Once the LAND RECOVERY buses are shed they do not return automatically even when normal power is restored — they must be brought back by pressing LAND RECOVERY to ON. Press it on any approach that has been through EMER CONFIG. Also: the QRH summary does not cover the RAT scenario; above 260 kt the EMER GEN has a windmill credit.

Key takeaways

References

Per FCOM PRO-ABN-ELEC (both branches in full: the coupling-does-not-yield clause, the BUS TIE OFF sandwich, engine anti-ice forced +1.5 %, the WEIGHT/CG verbatim, the full APPR PROC sequence, MAX FL 350 / 330 / M0.82 / ALTN LAW PROT LOST) and FCTM PR-AEP-ELEC (the two cause families, the QRH-does-not-cover-RAT boundary, the 260 kt windmill credit, left-seat PF, the airport decision, the RAT-first anti-disconnect reason, the two-state remaining-systems table, the restoration clause verbatim), with the QRH 16.01A/16.02A summary and SYS REMAINING table as the post-ECAM working baseline. The "BUS TIE OFF island isolation" reading and the "slat / green-pressure dip" linkage are integrative readings built on the verbatim procedure steps and the FCTM cause analysis. As the ultimate emergency, this article carries no separate MEL section.

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