Starting System

"The engine starting system consists of an air turbine starter and a start valve. The start valve admits air supplied by the pneumatic system to operate the starter. The FADEC electrically controls the start valve. On ground, in the event of an electrical control failure, the start valve can be manually operated by a handle."

The essence of starting: borrow a breath of outside air and spin N3 up to a self-sustaining speed. The breath comes from one of three lenders; the pilot's entire contribution is three moves (selector — MASTER — selector back); and the FADEC watches with five pairs of eyes for the five classic start diseases. That manual handle in the FCOM's last sentence lives behind the left fan-cowl door 415BL (article 02's walkaround map) — the ground-start method of last resort when electrical control is gone.

1. The hardware pair, and three air lenders

The air turbine starter (EGM front face, QAD-mounted): an air turbine drives a reduction gear train — converting high speed/low torque into low speed/high torque — through a ratchet (pawl) clutch to the output shaft, into the gearbox, and onto the HP spool (N3). Three easily missed details: the casing carries a containment ring (a starter is itself a small turbine machine, and its turbine fragments must be caught); it has its own independent oil system — sight glass, filler plug, and a drain plug with its own magnetic chip detector, so its blood test belongs to the starter, not to the engine oil system; and the clutch pawls disengage automatically once N3 outruns the starter's output speed — the very pawls that the "no running engagement" limitation of article 00 protects.

The start control valve (SCV) (lower right of the LP case, between the two duct runs): a dual-winding solenoid valve — one winding per FADEC channel; energised open, de-energised closed. In the early seconds of a start it is energised by aircraft power (conditioned to DC in the PCU); once the FADEC's own alternator can carry the load, the supply hands over — another instance of "aircraft power only opens the show" (article 04's 8 % switchover philosophy).

The three lenders:

"The air to turn the pneumatic starter is supplied from one of the sources which follows: ‐ the other engine through the cross-bleed system ‐ the Auxiliary Power Unit (APU) ‐ a ground air supply source."

The system schematic (read directly) sorts the control wiring into three line types — air circuit, analog hardwire and ARINC bus: the three cockpit controls (MASTER, START selector, MAN START pushbutton) pass as discretes through the EIVMU onto the ARINC path into both EEC channels, while the EEC drives the SCV solenoid by hardwire and reads back its position switch — the source of the START VALVE four-state symbol on the ENG SD page (article 15).

2. The three moves

 initial state: MASTER OFF ┊ selector NORM ┊ MAN START dark
     │
 MOVE 1: selector → IGN/START
     │   (ENG SD page appears, full parameters; pack valves close;
     │    if MASTER untouched for 30 s → packs reopen, SD page withdraws)
 MOVE 2: MASTER → ON
     │   LP valve opens → SCV opens → ignition (ground: N3 25–30 %; flight: immediate)
     │   → HP valve opens → at N3 ≥ 50 %: SCV closes (fully closed in 10 s) + ignition off
 MOVE 3: selector → NORM
     │   (left unselected: 15 s after all engines running, SD auto-switches pages)
     ▼
 【interrupt】 at any moment, MASTER → OFF: LP+HP valves close · ignition off · SCV closes

3. The automatic start: full authority and the five diseases

"This sequence is under the FADEC's full authority, which controls the: ‐ Start valve ‐ Igniter(s) ‐ Fuel HP valves. It provides: ‐ Detection of hot start, hung start, surge, no light up or N1 rotor locked ‐ FAULT announcement with specific ECAM message ‐ Start abort on ground (high pressure valve closure, start valve closure, ignition stopped) and automatic engine dry crank after start abort. One further automatic start attempt will be initiated by the FADEC after cranking, except in the case of N1 rotor locked. If this start attempt fails, the start will be aborted."

The hidden script inside that paragraph deserves spelling out: first attempt fails → the FADEC aborts (HP valve closed, SCV closed, ignition off) → dry-cranks the engine by itself to purge fuel vapours → tries once more on its own (with both igniters this time, powered once EGT is below 150 °C — article 11) → only a second failure hands the problem back to you. The single disease that gets no second chance is N1 rotor locked — if the fan itself cannot turn, no amount of purging helps. And the abort logic has a deliberate blind spot:

"Automatic start abort is inhibited on ground, when N3 is above 50 % or in flight."

On the ground above 50 % N3 the engine is moments from self-sustaining — cutting it down then is more dangerous than letting it finish. In flight the inhibition is absolute: there is no automatic giving-up in the air; whether to persist or to stop is entirely the crew's decision (the keynote of in-flight relights, article 26). The AMM's start-malfunction table aligns disease, consequence and ECAM name — SCV stuck closed = no assisted start; SCV stuck open = continued running will damage the starter; HP valve stuck closed = no start; high EGT, surge, no light-up, fan locked = ground abort — the base table that article 23 turns into procedures.

4. Move 2's timetable — the precise numbers

"‐ The LP fuel valve opens ‐ The engine start valve opens (except in flight in the stabilized windmill zone) ‐ The ignition starts: On ground: when N3 is between 25 and 30 % / In flight: Immediately. ‐ The HP fuel valve opens ‐ When N3 ≥ 50 %, the engine start valve closes (the valve is fully closed in 10 s) ‐ The ignition stops."

Three "whys" hide in the timetable (synthesis). Ignition waits for 25–30 % because the compressor must first establish a minimum airflow — only then is the fuel/air mixture both lightable and stable (in flight the windmilling engine already has flow, hence "immediately"). The starter retires at 50 % because turbine power can now self-accelerate the spool; hanging on past that point recreates the very speed-mismatch problem the engagement limits exist to prevent. The 10-second closure is a soft shutoff that spares the bleed ducting a water-hammer. And Move 1 carries its own 30-second rule: select IGN/START but leave the MASTER untouched for 30 seconds and the packs reopen, the SD page withdraws — the system concludes you were merely passing through, and returns the borrowed bleed air to the cabin.

5. The manual start: the FADEC steps back

"In the manual start sequence, the FADEC has limited control. As a result, the flight crew must monitor engine acceleration. … The FADEC: ‐ Opens the engine start valve when the flight crew: Sets the ENG START selector to IGN/START / Sets the ENG MAN START pb-sw to ON ‐ Opens the HP shutoff valve, and operates both igniters when the flight crew sets the ENG MASTER lever to ON ‐ Closes the engine start valve, and cuts off the ignition when N3 reaches 50 %. … The FADEC provides a passive survey of the engine during the starting sequence."

The essential difference between automatic and manual is one sentence: who decides the moment fuel is introduced. Automatically, the FADEC waits for 25–30 % N3 and schedules the fuel; manually, MASTER ON opens the HP valve and fires both igniters at once — the fuel timing becomes the moment you move the lever, and the hot-start risk plus the monitoring duty transfer to the human (the supplementary procedure that manages this rhythm is in article 34). The FADEC does not fully let go: it still closes the SCV at 50 % and keeps a passive survey. One adjoining rule completes the picture: in flight, any start below 50 % N3 is automatically starter-assisted — the FADEC makes that call itself, the other face of the 50 % boundary that shapes the relight envelope of article 26.

6. Dry crank and wet crank

"A dry cranking cycle enables the engine to be ventilated to remove fuel vapors after an unsuccessful start attempt on ground. Cranking can be manually selected by setting the ENG START selector to CRANK and the ENG MAN START pb-sw to ON (ENG MASTER lever to OFF)."

Wet crank is the "fuel flows but absolutely nothing sparks" leak-check: the CRANK position's hardware-level no spark anywhere (article 11) is its safety precondition, and a dry crank to purge always follows. From a dry crank, a manual start can be entered directly (selector to IGN/START, MASTER ON).

7. With the EIVMU failed: four functions become two

"In the case of EIVMU/EIU failure, the FADEC uses a backup signal from the ENG MASTER lever and the alternate start/ignition signal to control: ‐ An automatic start, or ‐ A dry crank, or ‐ Continuous ignition. Manual starting is no longer available."

A memory handle (synthesis): the backup signal chain carries only coarse words — the MASTER state and one alternate discrete — and cannot convey fine words like the MAN START pushbutton. So everything that requires pressing MAN START — manual start and wet crank — is gone, while everything the FADEC decides for itself — automatic start, dry crank, continuous ignition — survives. The "what remains" inventory of the EIVMU FAULT alert (article 19) is hereby complete.

8. Where the starting system meets the failure chapters

Self-test

[!note]- Q1. In a ground automatic start, when does ignition begin and when does the starter retire? Ignition begins between 25 and 30 % N3 (in flight: immediately, because the windmilling engine already has airflow). At N3 ≥ 50 % the start valve closes — fully closed within 10 s — and ignition stops.

[!note]- Q2. The first attempt fails to light. What does the FADEC do next — and which disease gets no retry? Abort (HP valve, SCV, ignition all closed/off) → automatic dry crank to purge vapours → one automatic retry (both igniters, once EGT < 150 °C). A second failure ends the matter. N1 rotor locked gets no retry — a fan that cannot turn cannot be purged into health.

[!note]- Q3. When is the automatic abort not available? On the ground above 50 % N3 (the engine is nearly self-sustaining; cutting it then is worse than finishing) — and always in flight: the air has no automatic surrender; persistence or abandonment is the crew's call.

[!note]- Q4. Configuration and purpose of a wet crank? Selector CRANK (hardware-guaranteed no spark) + MAN START ON + MASTER ON (fuel flows through the open shut-off valve) — a fuel leak check, watching the exhaust for vapour; followed by a dry crank to purge, with the starter duty-cycle clock of article 00 running throughout.

[!note]- Q5. The EIVMU has failed. How do you start that engine? Use the automatic start — the MASTER backup signal plus the alternate start/ignition discrete still support automatic start, dry crank and continuous ignition. Manual start and wet crank are unavailable (nothing can carry the MAN START button's "fine words").

Key takeaways

References

• FCOM DSC-70 (starting system) — system composition and the manual handle, full-authority sequence and five-disease detection, abort/dry-crank/retry script and its inhibitions, the Move-2 timetable, manual-start division of labour, in-flight starter-assisted rule, dry-crank selection, EIVMU-failure survivals.
• AMM 80-10 (cranking, D/O) — dry/wet crank configurations and purposes, the three air sources, the start-malfunction table.
• AMM 80-11 (starter and SCV, D/O) — reduction train, pawl clutch, containment ring, independent oil with MCD; dual-winding solenoid and the aircraft-power-first arrangement.
• ASM (starting system schematic, read directly) — the three line types, EIVMU discrete routing, SCV solenoid and position switch.
• FCOM start-sequence figure (read directly) — the three-move control timeline and interrupt path.
• Integrative synthesis (marked in text): the three timetable "whys"; the who-times-the-fuel distinction; the coarse-words/fine-words memory handle.

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.