Limitations & Supplementary Procedures

Article 12 taught the standard start. This article is the official manual for six non-standard postures — when to change posture, and where each posture's dedicated risk point (its CAUTION or WARNING) lies. The limitations themselves were laid out in full in article 00; here the start-related ones (starter duty cycle, engagement limits, EGT start limit) return to their operational context.

1. Manual start — when the fuel timing moves to human hands

"Manual starting is recommended in the following cases: ‐ After aborting a start, because of: Engine stall / Engine EGT overlimit / Low start air pressure ‐ When expecting a start abort, because of: Degraded bleed performance, due to hot conditions, or at a high-altitude airfields / An engine with a reduced EGT margin in hot conditions, or at a high-altitude airfields / Marginal performance of the external pneumatic power group."

Six cases, one common denominator (synthesis, via article 12): the start's energy budget is tight — weak air means slow acceleration, and the same fuel burns hotter. The automatic start's fixed plan tends to hit the abort line on a tight budget; a manual start hands the fuel timing to you, introducing fuel only when N3 is higher and airflow stronger — the EGT margin widens on the spot.

Two notes form the manual start's guardrails. First, residual EGT above 100 °C: motor the engine to cool it first — the cooling threshold of article 11, which automatic mode would honour for you, becomes your own discipline in manual mode. Second, the abort comes in two sequences: suspecting trouble before MASTER ON → MAN START pushbutton OFF suffices; after MASTER ON → MAN START OFF first, then MASTER OFF — fuel has already entered, and the close-out must be complete.

2. External pneumatic start — protect the air conditioning first

"Before connecting the air start unit: PACK 1 OFF / PACK 2 OFF — Packs are selected off to prevent any possible contamination of the packs by the air start unit."

Ground-cart air is not necessarily clean — oil mist, dust (synthesis). Switching the packs off takes the air-conditioning system out of that foreign air's downstream path.

3. Crossbleed start — two iron rules

"CAUTION: Do not perform the crossbleed engine start procedure during pushback. Simultaneous use of engine bleed supply and external pneumatic power supply is prohibited."

One engine must be running to supply the other's start; before the second start, APU BLEED OFF — the supplying engine's bleed valve reopens and the crossbleed valve logic follows configuration, with the supplying engine's thrust increased as required.

The two rules' reasons (synthesis): a crossbleed start during pushback means the supplying engine must add thrust to hold duct pressure — against a tug holding the nose. And engine bleed plus external air simultaneously means two pressure sources fighting — duct and cart both lose. This procedure is the execution body of article 23's "consider X BLEED if pressure is low" — the supplying engine pushes the duct pressure up to where the starter needs it (the other end of article 15's starter-inlet reference).

4. Battery start, and the etiquette of disconnecting ground power

The battery-only start (no APU generator, no external power) allows two ground air carts in parallel when pressure or flow looks marginal. And one piece of etiquette rides with it — disconnect external power only after both engines run, and:

"WARNING: Disconnection of the external power with the EXT PWR pb-sw ON may cause injury to the ground engineer. Request disconnection of the external power only with the EXT PWR pb-sw AVAIL."

5. Manual start-valve operation — why the affected engine starts first

"BEFORE ENGINE START: Advise ground crew to prepare for manual engine start valve operation. WARNING: To ensure safety of the ground crew when starting an engine with manual operation of the start valve, the flight crew should start the affected engine first."

The reason (synthesis): operating the valve by hand means a person standing at the engine nacelle (article 02's access door, article 12's hand-crank fitting). Start the healthy engine first, and that person must then work the crank inside the danger zone of a running engine. Affected engine first, healthy engine second — the operator stays clear of a turning intake. The procedure runs on the cabin-interphone channel with explicit ground clearance and the spoken "ENGINE 1(2) START" call — this is the full execution of article 23's STUCK CLOSED "fix the door" branch.

6. Dry crank — the manual entrance to a familiar script

"On ground, after: ‐ An unsuccessful manual engine start, or ‐ An unsuccessful automatic start not followed by an automatic dry crank, the flight crew can perform a dry crank cycle on the affected engine to remove the fuel vapors."

The entrance conditions are written precisely: an automatic start normally brings its own dry crank (article 12's abort script) — the manual cycle exists only for when the script didn't play: a failed manual start, or an automatic abort you interrupted.

7. The limitations, back in context — a quick-reference card

8. Scenario walk-throughs

High-elevation airport, hot afternoon, second start attempt coming. Change to the manual posture directly — and keep the duty-cycle clock ticking in your head.

Turnaround with APU bleed failed. Crossbleed start: first engine off the external cart (packs off), cart away, then crossbleed the second — never both sources at once.

A flight with START VALVE STUCK CLOSED. Article 23 diagnosed it; this article executes: advise the ground, affected engine first, interphone calls in step.

Battery-start ferry. Two air carts paralleled and ready; both engines running before anyone touches the ground power — and only on AVAIL.

Self-test

[!note]- Q1. High-elevation, hot day, marginal air cart — which posture, and why? Manual start — all three "expecting an abort" cases apply. Human-controlled fuel timing waits for higher N3 before introducing fuel, widening the EGT margin.

[!note]- Q2. Manual start, MASTER already ON, an alert appears — the abort order? MAN START pushbutton OFF first, then MASTER OFF (fuel is in; the close-out must be complete). Before MASTER ON, MAN START OFF alone suffices.

[!note]- Q3. The two crossbleed CAUTIONs? Never during pushback (the supplying engine's added thrust fights the tug); engine bleed and external air never simultaneously (two pressure sources in conflict).

[!note]- Q4. Why does the manual-valve start begin with the affected engine? The person on the crank stands at the nacelle — starting the affected engine first keeps them out of a running engine's danger zone while they work.

[!note]- Q5. When is a manual dry crank needed? After a failed manual start, or after a failed automatic start that wasn't followed by its automatic dry crank — the automatic script normally brings its own; you only supply the missing performance.

Key takeaways

References

• FCOM PRO (supplementary procedures — engine: manual start with its notes; external pneumatic start; crossbleed start; battery start; manual start-valve operation; dry crank) — all quoted verbatim; full line-by-line sequences per the manual, with the skeleton and risk points rendered here.
• FCOM LIM (engine) via article 00 — the duty-cycle, engagement, and EGT limits returned to context.
• Integrative synthesis (marked in text): the tight-energy-budget unification; the cart-contamination reading; the two iron rules' reasons; the personnel-safety logic of affected-engine-first.

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.