Engine Control Panels

The engine's entire cockpit interface amounts to five items: two lever sets (thrust and reverse), one key (the MASTER), one rotary selector (START), one pushbutton (MAN START) — plus the maintenance-only FADEC GND PWR button. Every earlier article has met them from the system side; this one closes the loop with the FCOM controls chapter, enumerating every function of every control, with emphasis on three things the earlier articles have not yet covered: the three meanings of the MASTER's FAULT light, the mechanical interlock between the levers, and the precise conditions of GND PWR.

1. ENG MAN START pushbutton (overhead panel)

"ON: ‐ Initiates the manual start sequence … when the ENG START selector is set to IGN/START, or ‐ Initiates the wet crank process … when the ENG START selector is set to CRANK and the ENG MASTER lever is set to ON, or ‐ Initiates the dry crank process … when the ENG START selector is set to CRANK and the ENG MASTER lever is set to OFF. Off: ‐ Aborts the manual start sequence … ‐ Stops the dry crank process …"

One button, three identities — and the identity is decided by the combination of the selector and the MASTER: with IGN/START it begins a manual start; with CRANK + MASTER ON, a wet crank; with CRANK + MASTER OFF, a dry crank. This is the control-panel view of the crank configuration table in article 12.

2. ENG START selector (centre pedestal)

"NORM: Normal mode of operation. IGN/START: ‐ Initiate the automatic or manual start sequences … when the ENG MASTER lever is set to OFF, or ‐ Initiate the ignitors in flight as required. CRANK: ‐ Initiate the dry crank process … ‐ Initiate the wet crank process … for maintenance purposes …"

Two notes. The second IGN/START function — energising the igniters in flight as required — is precisely the manual continuous ignition of article 11. And the official qualifier on wet cranking — "for maintenance purposes" — places it firmly in the maintenance domain (a fuel-leak check), not in the pilot's daily toolkit.

3. ENG MASTER lever and its two lights

MASTER ON serves four functions, routed by the configuration at the time: continuous ignition (engines running + selector at IGN/START), wet crank (CRANK + MAN START ON), automatic start (IGN/START), manual start (IGN/START + MAN START ON). MASTER OFF: shutdown, or start abort. The lights carry this article's most important new knowledge:

"FIRE light: A fire is detected in the corresponding engine. FAULT light: ‐ The position of the HP fuel shutoff valve is abnormal, or ‐ The automatic start sequence of the associated engine aborts, or ‐ There is a malfunction of the thrust control."

The FAULT light's three meanings belong to three entirely different chapters: an abnormal HP-valve position (articles 09/31), an aborted automatic start (articles 12/23), or a thrust-control malfunction (article 19). On seeing FAULT, identify which ECAM alert is present — the light itself does not discriminate.

Inside the switch: six stages, and a hardwired kill path

Electrically, each MASTER switch comprises six stages:

"The ENG/MASTER switches located on the panel 125VU comprise each six stages that supply respectively: ‐ the alternate starting through the EEC ‐ the reset of the EEC A and B channels ‐ the HP FUEL ON and HP FUEL OFF controls, through the EIVMU ‐ the excitation of the ENG MASTER SW SLAVE relay which cuts off the power supply of the LP fuel valve actuator ‐ the closure of the HP fuel shut-off valve."

So one lever movement simultaneously: signals the alternate start path, resets both EEC channels, commands HP FUEL ON/OFF through the EIVMU, excites the slave relay that de-powers the LP fuel valve actuator, and closes the HP shut-off valve. The last of those is implemented in the way most worth remembering — two torque motors, with the manual path hardwired:

"Two systems control the operation of the HP fuel shut off valve: ‐ a manual system directly wired to the ENG/MASTER switch which operates a torque motor that causes fuel shutoff in 0.5 seconds when energized, and latches in fuel off after being energized for 5.0 seconds. ‐ an automatic EEC controlled system which operates a second torque motor during starting mode. … fuel off takes priority over fuel on."

This answers a question every pilot should be able to answer (synthesis): shutting down with the MASTER depends on no computer. The manual fuel-cut path runs by hardwire from the switch to its own torque motor — with the EEC and EIVMU completely dead, this one switch still shuts the engine down (the same design language as the direct-wired thrust levers of article 04: the most vital commands skip the middlemen). And "fuel off takes priority over fuel on" guarantees that any conflict between the two systems resolves toward the safe side. The wiring schematic (read directly) adds one more layer of assurance: the HP FUEL SOV circuit breaker hangs on the 28 V DC essential bus — the manual kill path is powered at emergency grade — and shows the OPU and TOS torque-motor signal pairs landing on the same FMU terminals: the HP valve's three keyholders (MASTER, OPU, TOS) visibly in parallel (article 09). The LP valve is likewise dual-sourced: the FIRE pushbutton (the ATA-26 route) and the MASTER through the slave relay — the schematic evidence behind "the FIRE pushbutton is the LP valve's second key" in article 24.

4. Thrust levers and reverse levers: the mechanical interlock

"The flight crew can move each thrust lever forward the Idle (0) stop, when the associated thrust reverser lever is set to the stowed detent." — "The flight crew can move the thrust reverser lever backward the stowed detent (to the IDLE REV detent or MAX REV stop), when the associated thrust lever is set to the Idle (0) stop."

Mutual door-bolts: with forward thrust set, the reverse lever cannot be raised; with reverse selected, the thrust lever cannot advance — "forward thrust plus reverse simultaneously" is excluded at the mechanical layer, the hardware insurance behind the angle ledger of article 08. The gate inventory, for completeness: forward thrust has one stop and three detents (Idle stop / CL / MCT-FLX / TOGA); reverse has two stops and one detent (stowed stop / IDLE REV detent / MAX REV stop). The lever-mounted A/THR instinctive disconnect pushbuttons disconnect the autothrust (details belong to the auto-flight chapter).

5. ENG FADEC GND PWR pushbutton (maintenance panel)

"Off: The electrical network of the aircraft or the FADEC alternator automatically supplies the FADEC. ON: On ground, when pressed the electrical network of the aircraft supplies the FADEC for 5 min, when: ‐ The ENG FIRE pb-sw is not pressed ‐ The FADEC alternator does not supply the FADEC. The ON light comes on 2 s after the ENG FADEC GND PWR pb is pushed."

Each detail has a pedigree. The 5 minutes is the same figure as relay R1's post-shutdown window (article 06) — this button is simply the "borrow five more minutes" switch, used for maintenance data downloads and ground self-tests. The FIRE pushbutton not pressed condition mirrors R1's hardwired cut: in a fire state, nobody re-powers the FADEC. The 2-second lamp delay corresponds to the power-up self-test (synthesis, so marked).

6. Where the controls meet operations

Self-test

[!note]- Q1. The FAULT light is on. Name the three possibilities. Abnormal HP fuel shut-off valve position; automatic start sequence aborted; thrust-control malfunction. The ECAM alert discriminates; the light does not.

[!note]- Q2. The reverse lever will not lift. What is the most common normal reason? The thrust lever is not at the Idle stop — the mechanical interlock is doing its job (forward thrust and reverse can never coexist).

[!note]- Q3. GND PWR is pressed and the ON light stays dark. How long before that is abnormal? The design delay is 2 seconds. Beyond that, check the two conditions: the FIRE pushbutton must not be pressed, and the FADEC alternator must not already be supplying the FADEC (if it is, the button has no effect).

[!note]- Q4. What does MAN START ON do in each of its three configurations? Selector IGN/START → manual start; CRANK + MASTER ON → wet crank; CRANK + MASTER OFF → dry crank. The combination decides the identity.

[!note]- Q5. In two-engine cruise, the selector is turned to IGN/START. What happens? Manual continuous ignition on both engines (one igniter each, automatically doubling if it fails — article 11) — the first of MASTER ON's four configuration-dependent functions.

Key takeaways

References

• FCOM DSC-70 (controls — overhead, pedestal, maintenance panels) — MAN START functions, selector positions, MASTER functions and light semantics, lever gates and interlock, A/THR instinctive disconnect, GND PWR conditions and timing.
• AMM 76-12 (engine master control, D/O) — the six switch stages, dual torque motors with the hardwired manual path and fuel-off priority, LP-valve dual sourcing.
• ASM (engine master control schematic, read directly) — essential-bus breaker, slave relay, OPU/TOS torque-motor terminals in parallel.
• Integrative synthesis (marked in text): the no-computer-needed shutdown conclusion; the 2-second self-test reading; the combination-lock framing.

Independent study material, not an Airbus publication and not endorsed by the manufacturer. Always defer to the current operator FCOM, FCTM, and QRH for operational use.