In-Flight Relight

This article expands the third fork of article 25 — IF NO DAMAGE: ENG RELIGHT CONSIDER. The whole subject compresses into three numbers: 30 000 ft (the maximum altitude at which a relight is guaranteed), 50 % N3 (the dividing line between windmill and starter-assisted starts, article 12), and 30 seconds (twice over: the light-up window after fuel flow appears, and the drain wait before any retry). The procedure itself is short — what is long is the trail of mechanisms already laid in earlier articles: light-then-lean at altitude (article 05), both igniters in the air (article 11), and the automatic starter-valve opening covered here.

1. The envelope, and the two ways back

"Engine Relight Envelope — MAX GUARANTEED ALTITUDE: 30 000 ft."

How to read the word guaranteed (synthesis): below 30 000 ft, inside the envelope's speed band, a relight is demonstrated to succeed. Above it is not forbidden — it is not guaranteed. The all-engines-failure procedure's optimum relight speed of 270 kt / M 0.82 (article 33) exists precisely to hurry the aircraft back inside this envelope.

Within the envelope, two regions divide by N3 and airspeed — and the choice between them is not yours to make:

"If outside windmilling start envelope, FADEC opens starter valve."

You never select the method. If speed and rotation suffice (the windmill region), the wind does the turning; if not, the FADEC opens the start valve by itself and borrows bleed air to help — the in-flight face of article 12's "below 50 % N3, always starter-assisted" rule. This single fact explains the two "serve the air first" steps in the procedure below.

2. The procedure, line by line

"ENG MASTER OFF → THR LEVER IDLE → ENG START sel IGN/START → X BLEED OPEN → WING ANTI ICE (for starter assisted) OFF → ENG MASTER ON → ENG PARAMETERS (N3, EGT) MONITOR — Engine light up should be achieved within 30 s after fuel flow increases. Monitor N3. If uncertain about successful relight, move the thrust lever forward and check engine response."

The whys, chained (synthesis): MASTER OFF first gives the sequence a clean origin — and covers the case where lever or switch states are uncertain. X BLEED OPEN comes early so that when the FADEC decides on a starter-assisted start, the air is already at the door. Anti-ice off surrenders its bleed to the starter — the same send-the-air philosophy as the START VALVE NOT OPEN handling of article 23: what the starter needs is real pressure in the duct (the starter-inlet reference of article 15).

And then the field technique unique to the annotated procedure — interrogate it with the lever: a windmilling N3 and a freshly-lit idle N3 can be hard to tell apart. Push the thrust lever forward a little; the engine that answers is the one that's alive.

The successful ending (idle reached, ENG AVAIL appears — pulsing for a minute, article 15):

"ENG START sel NORM / TCAS MODE sel TA/RA — Check that the selector is at TA/RA since if the ENG SHUT DOWN procedure has been applied, the TCAS mode selector may have been set at TA position. / X BLEED AUTO / Affected SYS RESTORE."

The TCAS note is a handshake between procedures (synthesis): article 25's SHUT DOWN demoted TCAS to TA (one engine cannot honour an RA); now both engines live, and RA capability must be handed back. A relight is not just lighting an engine — it is reversing every setting the one-engine world changed. That is the spirit of Affected SYS RESTORE.

The failed ending:

"If no relight: ENG MASTER OFF — Wait 30 s before new start attempt (to drain the engine)."

The same physics as article 23's in-flight 30 seconds — the dump valve clearing the combustor (article 09). And remember: in flight there is no automatic abort (article 12) — whether to stop, and how many times to retry, is entirely yours.

3. The three relights, compared

Ordered by depth of human involvement (synthesis): at the instant of flameout the FADEC rescues by itself (auto); fumble the MASTER and flip it straight back, and it takes the shortcut (quick); shut down and thought through, you run the full sequence (this article). The common floor under all three is article 05's rule: at altitude, the moment of light-up triggers an immediate fuel-flow reduction against HP-compressor surge — whichever road you took there, the FADEC does the same thing at the flame.

4. Scenario walk-throughs

Article 25's fork lands on NO DAMAGE. Descend below FL 300, set the speed, and run this procedure once, line by line.

EGT surges during the relight. No automatic abort exists in the air — your hand is the abort: MASTER OFF, 30 seconds, then assess retry versus a single-engine approach.

All-engines scenario (article 33). This procedure is the single-engine template inside that larger drama — envelope awareness leads everything.

Debrief drill: have the trainee recite the two 30-seconds and their different identities — the light-up window after fuel flow, versus the drain wait after failure.

Self-test

[!note]- Q1. Dual flameout at FL 350 — can you relight straight away? 30 000 ft is the guaranteed ceiling — above it, no guarantee. The all-engines procedure's optimum relight speed (270 kt / M 0.82) exists to get you back inside the envelope quickly.

[!note]- Q2. Why open the crossbleed early, and who decides whether the starter is used? Pre-staging air for a possible starter-assisted start; the FADEC decides — outside the windmill envelope it opens the start valve itself. You never choose.

[!note]- Q3. Fuel flow appeared 40 seconds ago, N3 creeping, and you can't tell if it lit — what now? First, the time ledger: light-up belongs within 30 s. Then interrogate with the lever — push forward and watch the response; only a live engine answers. Still doubtful: MASTER OFF, 30 s drain, retry.

[!note]- Q4. The most-missed item in the successful close-out? TCAS back to TA/RA — the SHUT DOWN procedure may have left it at TA; the relight procedure carries an explicit check for it. Restoring the one-engine settings is part of the relight.

[!note]- Q5. Quick relight vs this procedure — the essential difference? Quick relight is the 30 s / N3 > 10 % shortcut (skips checks, ignores the selector, won't auto-stop). The procedural relight is the full post-assessment sequence — envelope, air sources, monitoring, and the restoration close-out.

Key takeaways

References

• QRH (engine relight in flight) — the complete procedure and the 30 000 ft guaranteed altitude.
• FCOM PRO (engine abnormal procedures, annotated relight section) — the automatic starter-valve opening, the lever-response verification, the TCAS handshake note, the 30 s drain — quoted verbatim. The relight envelope chart itself is graphical; the guaranteed altitude and region logic are rendered in text here, with the precise speed boundaries deferred to the chart (referenced again in the all-engines scenario of article 33).
• Integrative synthesis (marked in text): the reading of "guaranteed"; the step-by-step whys; the procedure-handshake framing; the three-relights ordering and their common floor.

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.