Engine Starting System — Air Starter, Start Valve, Start Sequence

Ignition gave the spark; this article gives the other half — getting the engine turning. It covers the air-turbine starter, the start valve, the three-step automatic start sequence, manual start, dry/wet cranking, and the FADEC's start-fault detection. It is the direct basis for Start Faults and Relight.

1. Starter and start valve

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 engine pneumatic start system supplies the power which turns the High Pressure (HP) rotor to start the engine.

Per DSC-70-80-30 and AMM 80-11-00, an air-turbine starter (FIN 5000ES) plus a start valve (FADEC electrically controlled, with a manual handle on the ground) turns the HP rotor (N3) to start — echoing the fuel system's HP-shaft-driven HP pump: start spins N3 up first. The start air:

The air necessary for the starting comes from the duct connecting precooler exchanger via a 4 in. (101.5998 mm) diameter duct to the SCV.

Per AMM 80-13-00, start air comes from the precooler via a 4-inch (101.5998 mm) duct to the SCV (start control valve).

2. Start / ignition control chain

Per the start-and-ignition-control schematic:

 ENG 1 + ENG START selector (CRANK/NORM/IGN-START) + MAN START (ON)
        │                                              │
        ▼                                              ▼
     EIVMU 1 ─────────────────────────────► ALTERNATE START & IGNITION LOGIC
        │                                              │
        │   ┌──── HARDWIRED BACKUP SIGNAL (bypasses EIVMU) ──┘
        ▼   ▼
     FADEC 1 (CH A / CH B)
        ├─► START VALVE
        └─► IGNITERS

The normal path runs via the EIVMU; a hardwired backup signal bypasses it straight to the FADEC (echoing the 02 EIVMU-failure backup). Both FADEC channels reach the start valve and igniters.

3. Automatic start — three steps

Initial configuration (DSC-70-80-30): ENG MASTER OFF, ENG START NORM, ENG MAN START OFF.

Step 1 — ENG START to IGN/START:

The flight crew must set the ENG START selector to IGN/START, leading to the following: ‐ The ENG SD page appears on the SD ‐ All engine parameters are available ‐ All pack valves automatically close. After 30 s, if the flight crew does not set the ENG MASTER lever to ON, the pack valves automatically open again…

The ENG SD page appears, all pack valves close (handing bleed to the starter), and a 30 s window opens.

Step 2 — ENG MASTER to ON (the sequence body, with the key N3 thresholds):

‐ 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)…

Step 3 — ENG START to NORM:

The automatic engine start is finished. The flight crew must set the ENG START selector to NORM. On ground the WHEEL SD page replaces the ENG SD page. In flight the CRUISE SD page replaces the ENG SD page. If ENG START selector is not switched to NORM, the ENG page is automatically replaced… 15 s after all engines are running.

The N3 thresholds (all verbatim):

4. FADEC control and start-fault detection

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.

Per DSC-70-80-30, the FADEC runs the whole sequence and detects hot start, hung start, surge, no light-up or N1 rotor locked, with a FAULT + specific ECAM message and, on the ground, a start abort (close HP valve, close start valve, stop ignition) followed by an automatic dry crank. Handling of the five is in Start Faults.

5. Manual start

If an automatic start is not successful, the flight crew can perform a manual start. In the manual start sequence, the FADEC has limited control. As a result, the flight crew must monitor engine acceleration. To perform a manual start, the flight crew must: ‐ Set the ENG START selector to IGN/START ‐ Set the ENG MAN START pb-sw to ON ‐ Set the ENG MASTER lever to ON.

In a manual start the FADEC has limited control and the crew must monitor acceleration; steps: ENG START → IGN/START, ENG MAN START → ON, ENG MASTER → ON.

6. Cranking — dry and wet

There are two modes of engine cranking in which the engine can be motored, dry or wet. To dry motor an engine is to turn the engine with the pneumatic starter.

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).

Per AMM 80-10-00 and DSC-70-80-30: two cranking modes, dry and wet; dry cranking turns the engine on the pneumatic starter to ventilate fuel vapour after an unsuccessful ground start (ENG START → CRANK + ENG MAN START → ON, ENG MASTER OFF; stop via MAN START OFF or ENG START NORM).

7. ENG START selector and counterintuitive points

[!warning]- The starter turns the HP rotor (N3), and the sequence runs on N3 The air starter drives the HP rotor (N3) (AMM 80-11); ignition at N3 25–30 %, start valve closes at N3 ≥ 50 % (DSC-70-80-30). The whole start is watched on N3, not N1.

[!warning]- All pack valves close during start Setting IGN/START closes all pack valves (DSC-70-80-30) — bleed goes to the starter. If ENG MASTER is not set ON within 30 s, the pack valves reopen.

[!warning]- In the stabilised windmill zone the start valve does not open Step 2's "start valve opens" has an exception: not in flight in the stabilised windmill zone (DSC-70-80-30) — windmill speed is already enough, no starter needed. Directly relevant to windmill relight.

Self-test

[!note]- Q1. Starter type, which rotor, and the air source? An air-turbine starter (5000ES) turning the HP rotor (N3); air via the precooler → 4-inch duct → SCV.

[!note]- Q2. Step 2 (MASTER ON) — what happens, with the key N3 thresholds? LP valve opens → start valve opens → ignition (ground N3 25–30 % / in-flight immediately) → HP valve opens → N3 ≥ 50 % start valve closes (10 s).

[!note]- Q3. What start faults does the FADEC detect? hot start / hung start / surge / no light-up / N1 rotor locked — with FAULT + ECAM, ground start abort + automatic dry crank.

[!note]- Q4. Manual vs automatic start? Manual: FADEC has limited control, crew must monitor acceleration; IGN/START + MAN START ON + MASTER ON.

[!note]- Q5. What is dry crank for, and how is it selected? Ventilate fuel vapour after an unsuccessful ground start; ENG START → CRANK + MAN START → ON (MASTER OFF).

Key takeaways

References

• FCOM DSC-70-80-30 — starting system; three-step automatic sequence (N3 25–30 % ignition, ≥ 50 % start-valve closure in 10 s, 30 s / 15 s windows); manual start; dry crank; fault detection.
• AMM 80-11-00 §1 — pneumatic start system turns the HP rotor.
• AMM 80-13-00 §1 — start air via precooler → 4-inch duct → SCV.
• AMM 80-10-00 §1 — two cranking modes dry/wet; dry motor on the pneumatic starter.
• Start-and-ignition-control schematic — ENG START/MAN START → EIVMU → FADEC (CH A/B) → start valve + igniters, hardwired backup.

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.