Engine Overview & Limitations

The A330 covered in this series is powered by two Rolls-Royce Trent 700 high-bypass turbofans. This opening article does two jobs at once. First, it builds the panoramic map of the powerplant — what the seven official sub-systems are, what each one does for the aircraft, and which article in this chapter takes each one apart. Second, it lays down the complete set of engine limitations from the FCOM limitations chapter, in full, so that every later article can refer back to a single authoritative baseline instead of re-quoting numbers piecemeal.

If you only have time for one article in this chapter, this is the one: everything else hangs off the skeleton built here.

1. More than thrust: the engine as the aircraft's power source

The FCOM introduces the powerplant in a single sentence:

"The aircraft has two Rolls-Royce Trent 700 engines that supply power to the aircraft."

That wording deserves a second look. It says the engines supply power to the aircraft — not merely "produce thrust". The distinction is real and operationally important. Through its accessory gearbox, each engine drives an IDG (electrical generation), one or two engine-driven hydraulic pumps (hydraulic generation), and supplies bleed air from its compressor (pneumatic generation, engine starting, air conditioning, anti-ice). Thrust is simply the most visible product of a machine that is, in truth, the aircraft's prime mover for every onboard power system.

This is why losing one engine never means losing "half the thrust" and nothing else. It means simultaneously losing one generator, one or more hydraulic pumps, and one bleed source — a resource cascade that the single-engine articles later in this chapter (engine failure and single-engine operations) account for line by line. It is also why ATA-70 sits at the centre of the whole aircraft-systems syllabus: hydraulics, electrics and pneumatics are all consumers; this chapter describes the producer.

The FCOM then gives the official decomposition of the powerplant into seven blocks:

"The engines are turbofan engines that have: ‐ A high bypass ratio, ‐ A Full Authority Digital Engine Control (FADEC), ‐ A fuel system, ‐ An oil system, ‐ An air system, ‐ A thrust reverser system, ‐ An ignition system and a start system."

These seven items are the manufacturer's own table of contents for the engine, and they are the skeleton on which the thirty-six articles of this chapter are built.

2. The seven systems and where each one is covered

A brief word on each, before the limitations.

The turbofan proper. The Trent 700 is a triple-spool design: LP, IP and HP rotors on three concentric shafts, each free to run at its own optimum speed with no mechanical connection between them. This is why the A330 cockpit shows three spool speeds — N1, N2 and N3 — where a twin-spool type shows only two. The full anatomy, from the spinner to the common exhaust nozzle, is in article 01; the pylon, cowls, accessory gearbox and drains that attach it to the aircraft are in article 02.

FADEC. "Full authority" is a term of art, not marketing: there is no mechanical linkage of any kind between the cockpit and the fuel valve. The thrust levers are an electrical request to the EEC (Engine Electronic Controller), a two-channel computer mounted on the fan case that owns every actuator on the engine. The FADEC even carries its own electrical generation — a dedicated magnetic alternator — so that once the engine is running, the loss of every aircraft electrical bus does not disturb engine control. Architecture and power supply are covered in article 04, the control laws and protections in article 05, and the engine–aircraft interface unit in article 06.

Fuel system. The engine-side fuel system takes over at the LP fuel shut-off valve (everything upstream belongs to ATA-28) and does three jobs with one fluid: fuel is the energy source, the hydraulic muscle for engine actuators (VSVs and others are fuel-powered), and a cooling medium for the oil system and the FADEC. "Shutting down the engine" is, mechanically, the act of closing the LP and HP fuel shut-off valves.

Oil system. Lubrication and cooling, of course — but equally the engine's blood sample. Oil pressure, temperature, quantity and the magnetic chip detectors form a continuous health report to the cockpit. The indicated oil pressure is actually a differential pressure, a subtlety left to article 10.

Air system. The air the engine keeps for itself: variable stator vanes and bleed valves manage the compressor's surge margin, the internal air circuit cools and seals the rotating machinery and balances axial loads, and turbine case cooling trades a little fan air for measurable cruise fuel burn. Note the boundary: bleed air supplied to aircraft users (packs, anti-ice) belongs to ATA-36; this chapter covers only the engine's own air.

Thrust reverser. The Trent 700 reverses fan (cold-stream) flow only — four pivoting blocker doors redirect bypass air forward while the core stream continues aft. Because the bypass stream carries most of the thrust on a high-bypass engine, reversing it is enough. An uncommanded deployment in flight is a severe event, so the doors are held by three independent levels of locking — the failure spectrum of that lock system is in article 32.

Ignition and starting. Two independent high-energy igniter systems (A and B) and a pneumatic starter motor that spins the N3 shaft through the start control valve. A normal ground start is fully FADEC-managed — the pilot moves one switch, and the FADEC sequences air, fuel and ignition while monitoring for the classic start malfunctions, aborting on its own if needed.

3. Chapter map — thirty-six articles in six groups

 A. Overview & engine proper          B. FADEC & thrust              C. Sub-systems
 ┌──────────────────────────┐   ┌──────────────────────────┐   ┌─────────────────────┐
 │ 00 Overview & limitations │   │ 04 FADEC architecture    │   │ 09 Fuel             │
 │ 01 Triple-spool core      │   │ 05 Control laws & prot.  │   │ 10 Oil              │
 │ 02 Accessory drive/nacelle│   │ 06 EIVMU interface       │   │ 11 Ignition         │
 │ 03 Air, cooling & surge   │   │ 07 EPR & N1 modes        │   │ 12 Starting         │
 └──────────────────────────┘   │ 08 Thrust levers         │   │ 13 Thrust reverser  │
                                └──────────────────────────┘   │ 14 Parameter sensing│
                                                               └─────────────────────┘
 D. Cockpit interface              E. Failure spectrum (16 articles — the heart)
 ┌──────────────────────────┐   ┌──────────────────────────────────────────────────┐
 │ 15 EWD/SD indications     │   │ 18 Alerts overview   19-24 computer/thrust/      │
 │ 16 Control panels         │   │ start/fire families  25-27 failure/relight/stall │
 │ 17 Fire detection i/f     │   │ 28-33 overlimit/vibration/oil/fuel/reverser/     │
 └──────────────────────────┘   │ all-engines-failure                              │
                                └──────────────────────────────────────────────────┘
 F. Operations close-out: 34 Limitations & supplementary procedures · 35 MEL & ETOPS

Sixteen of thirty-six articles — nearly half the chapter — deal with failures. That proportion is not editorial taste: in the FCOM itself, the engine abnormal-procedures section runs to 124 pages and roughly 55 alerts, more than twice the bulk of the system-description section. A pilot-oriented engine course weights failures heavily because the source material does.

4. Engine limitations — the complete FCOM set

Everything below comes from the FCOM limitations chapter, quoted in full. Later articles refer back here rather than re-quoting.

4.1 EGT limits — why 900 °C and 920 °C are both "the limit"

"THRUST SETTING/EGT LIMITS — Takeoff(1) and Go-around: All engines operative, 5 min; One engine inoperative, 10 min — 900 °C (920 °C, 20 s). Maximum Continuous Thrust (MCT): Not limited, 850 °C. Starting: On ground 700 °C, In flight 850 °C. (1) Includes TOGA, FLEX, and DERATE thrust modes."

The 900/920 pair is the most commonly confused number set in the engine limitations, so it is worth locking down with the display logic that the EWD itself uses. Per the engine-indications section of the FCOM:

"The EGT red limit is 920 °C. … Red: The EGT is above the EGT red limit. The current EGT: ‐ Is between 900 °C and 920 °C for more than 20 s, or ‐ Exceeds 920 °C."

Put the two quotes together and the correct reading falls out:

• 900 °C is the working limit for takeoff and go-around. Any EGT up to 900 at takeoff thrust is legitimate, for up to 5 minutes all-engines (10 minutes single-engine).
• 920 °C is the absolute red line. The band between 900 and 920 is a 20-second transient allowance — a brief excursion during the takeoff transient is by design; staying in that band beyond 20 seconds constitutes an exceedance.
• 920 °C may not be exceeded at all, even momentarily.
• Two further gates stand alone: MCT 850 °C with no time limit, and starting limits of 700 °C on the ground and 850 °C in flight. The ground-start limit is the lowest figure in the table for a physical reason: during a start the mass flow through the turbine is tiny, so the blades enjoy the least convective cooling of any operating condition — the same indicated EGT does more damage.

[!warning]- Common misreading: "the red line is 920, so 910 on takeoff is fine" Not quite. An EGT of 910 °C that persists beyond 20 seconds turns the indication red and constitutes an exceedance event. The figure to supervise day-to-day is 900; 920 is the ceiling for transients only. The EGT OVERLIMIT alert and the exceedance handling that follows are covered in article 28.

4.2 Shaft speed limits — three spools, three red lines

"SHAFT SPEEDS — Maximum N1 99 %. Note: The N1 limit depends on the ambient conditions and on the configuration of the engine air bleed. These parameters may limit N1 to a value that is less than the above-mentioned N1 value. Maximum N2 103.3 %. Maximum N3 100 %."

There is a memorable asymmetry here: the fastest spool (N3) has the most ordinary red line (100 %), the slowest spool (N1) never even reaches 100 (99 %), and the middle spool (N2) is allowed "over a hundred" (103.3 %). The percentages are each referenced to that spool's own datum speed, so they are not comparable across spools — 103.3 % N2 does not mean the IP spool turns faster than the HP spool.

Note also the N1 caveat in the quote: 99 % is only the paper ceiling. The actual usable N1 on any given day is computed by the FADEC from ambient conditions and bleed configuration, and may be lower — this is precisely the N1 rating limit you see displayed on the EWD (article 15). What happens when a spool exceeds its red line — and the entirely separate, higher thresholds at which the independent overspeed protection unit takes action — is the subject of article 28.

4.3 Oil limits — three hard numbers and the 15-quart rule

"OIL — OIL TEMPERATURE: Maximum continuous temperature 190 °C. Minimum temperature before takeoff 50 °C. OIL QUANTITY: The minimum oil quantity is the highest value of: ‐ 15 qt, or ‐ 6 qt + estimated consumption. Average estimated consumption = 0.7 qt/h. OIL PRESSURE: Minimum oil pressure 25 PSI."

The quantity rule rewards a moment's arithmetic. The formula 6 qt + 0.7 qt/h × flight time only exceeds the flat 15-quart floor when 0.7 × hours > 9 — that is, on sectors longer than roughly 12.8 hours. A worked example: for a planned 14-hour sector, 6 + 0.7 × 14 = 15.8 qt, so the minimum departure quantity rises to 15.8 qt. For the overwhelming majority of flights the answer is simply 15 qt, but the formula is the binding rule and it bites on ultra-long-haul.

The 25 PSI figure will recur throughout this chapter: it is simultaneously the limitation, the red band boundary on the SD oil-pressure scale, and the trigger value of the OIL LO PR warning (article 10, article 30).

4.4 Starter limits — duty cycle and re-engagement

"STARTER — Starter maximum continuous operation is 5 min. Two 3 min duty cycles and a consecutive 1 min cycle is permitted with run down to zero N3 between each cycle. After one continuous operation, or the three cycles, wait 30 min to allow the starter to cool. No running engagement of the starter when the N3 is above 10 % on ground, or 30 % in flight."

The re-engagement prohibition protects the starter's clutch: engaging a starter against a spinning spool with too great a speed mismatch hammers the engagement pawls. The two thresholds differ — 10 % N3 on the ground but 30 % in flight — because a windmilling engine in flight will not spool down to near-zero N3 no matter how long you wait; the limit is relaxed to make in-flight starter assistance physically possible. The start sequence itself is in article 12, and start malfunctions in article 23.

4.5 Reverse thrust — three prohibitions and one permission

"REVERSE THRUST — Selection of the reverse thrust is prohibited in flight. Backing the aircraft with reverse thrust is not permitted. Maximum reverse should not be used below 70 kt. Idle reverse is permitted down to aircraft stop."

The 70-knot rule has a concrete aerodynamic basis (developed fully in article 13): below that speed the forward-redirected efflux can be re-ingested by the engine's own intake — hot-gas re-ingestion plus debris blown forward along the runway, a combined surge and FOD hazard. Idle reverse moves far less air, which is why it remains permitted all the way to a stop.

4.6 Reduced-thrust takeoff — FLEX and DERATE have different forbidden zones

"FLEX TAKEOFF — Takeoff at reduced thrust, so-called as FLEX takeoff, is permitted only if the airplane meets all performance requirements at the takeoff weight, with the operating engines at the thrust available for the flexible temperature (TFLEX). Takeoff at reduced thrust is permitted with any inoperative item affecting the performance only if the associated performance shortfall has been applied to meet the above requirements. FLEX takeoff is not permitted on contaminated runways. TFLEX cannot be: ‐ Higher than TMAXFLEX, equal to ISA + 60 °C. ‐ Lower than the flat rating temperature (TREF). ‐ Lower than the actual OAT."

The middle sentence is the one most often skipped and most often relevant on the line: when dispatching with an MEL item that affects performance, FLEX is not automatically available — it remains permitted only if that item's performance penalty has already been fed into the takeoff performance computation. In other words, "cleared to dispatch" and "cleared to FLEX" are two separate checks.

"DERATED TAKEOFF — Selection of TOGA thrust is not permitted when a derated takeoff is performed, except when requested in any abnormal or emergency procedures. The use of reduced thrust takeoff (FLEX takeoff) is not permitted in association with derated takeoff. The use of derated takeoff is permitted regardless of the runway condition (dry, wet, or contaminated)."

The deep difference between the two reduced-thrust methods explains every line of their rules. FLEX is "pretending it is hotter than it is": the FADEC is told an assumed temperature above actual OAT, but the rating structure itself is untouched — so pushing the levers to TOGA at any moment instantly restores full rated thrust. That recoverability is FLEX's safety net, and the contaminated-runway prohibition exists because the assumed-temperature performance method is not valid on contaminated surfaces. DERATE is "installing a smaller engine": the rating itself is reduced, and the performance data — including minimum control speeds (VMC) — are computed for that smaller engine. That is why TOGA selection during a derated takeoff is prohibited without a procedural requirement: a sudden thrust increase invalidates the VMC basis, and with an engine failed the aircraft may not be directionally controllable. It is also why DERATE, unlike FLEX, is permitted on contaminated runways — its performance accounting is honest from the start. Mechanisation and handling of both are in article 08.

4.7 Two remaining limitations

"Engine crosswind limit at takeoff: 32 kt (gust included)." "The use of soft go-around is prohibited with one engine inoperative."

The 32-knot figure is an engine crosswind limit — it protects the fan against intake-flow distortion in strong crosswinds during the takeoff roll, and is distinct from any aircraft-handling crosswind guidance. Its very location in the engine limitations section, rather than the aircraft-general section, is the clue to its purpose. The soft go-around prohibition with one engine inoperative is equally direct: a single-engine go-around is already thrust-limited, and a deliberately softened thrust target would cut into margin that no longer exists (article 08 covers the soft-GA mode itself).

5. Alerts and dispatch — a preview

The engine abnormal-procedures section of the FCOM contains roughly 55 alerts; this chapter organises them into family articles — FADEC computer faults (19), FADEC environment and protection losses (20), thrust-mode degradations (21), thrust-lever faults (22), starting and ignition (23), the core-failure triplet of shutdown, relight and stall (25, 26, 27), exceedances and vibration (28, 29), oil and fuel-side faults (30, 31), reverser faults (32) and the all-engines-failure scenario (33). Six paper QRH procedures sit alongside the ECAM-driven ones. The full index, with the threat tiers and inhibition logic, is article 18.

On the ground, the MEL maps engine ECAM alerts to dispatch conditions item by item; engine dispatch is comparatively strict — many amber FADEC-family alerts that require no crew action in flight still carry dispatch limitations. The full mapping philosophy is article 35.

Self-test

[!note]- Q1. EGT reads 905 °C during the takeoff roll. Legal or not? Legal as a transient: 905 °C sits in the 900–920 band, which is permitted for up to 20 seconds. If it persists beyond 20 s the EWD indication turns red and the event becomes an exceedance. 900 °C is the working takeoff limit; 920 °C is the never-exceed ceiling.

[!note]- Q2. N2 indicates 101 %. Immediate thrust reduction required? Not on that number alone — the N2 red line is 103.3 %, the only spool red line above 100. Cross-check N1 (red line 99 %) and N3 (100 %) and look for an OVERLIMIT alert before acting.

[!note]- Q3. Planned 6-hour sector, oil quantity 12 qt before start. Acceptable? No. Minimum = the higher of 15 qt or 6 + 0.7 × 6 = 10.2 qt → 15 qt. 12 qt is below the limit.

[!note]- Q4. During a derated takeoff you encounter windshear after lift-off. May you push TOGA? Yes. The prohibition on TOGA during derated takeoff carries an explicit exception: "except when requested in any abnormal or emergency procedures." The windshear escape procedure commands TOGA, so TOGA is correct. What is prohibited is discretionary TOGA selection with no procedural basis — that is what invalidates the VMC assumptions.

[!note]- Q5. Why is FLEX prohibited on contaminated runways while DERATE is permitted? FLEX rests on an assumed-temperature performance method whose assumptions are not valid on contaminated surfaces. DERATE's performance data are computed genuinely for the reduced rating — runway state is already inside its accounting — so it remains available on dry, wet or contaminated runways.

Key takeaways

References

• FCOM LIM (engine limitations section) — thrust/EGT table, shaft speeds, oil, starter, reverse thrust, reduced thrust takeoff, crosswind, soft go-around (quoted verbatim above).
• FCOM DSC-70 (powerplant description, introduction) — engine type and seven-system decomposition.
• FCOM DSC-70 (engine indications) — EGT red-line display logic used as cross-check.
• Integrative synthesis (clearly marked in text): the "power source, not just thrust" framing; the physical rationale for the ground-start EGT limit, the starter re-engagement thresholds and the 70-kt reverse rule; the FLEX-vs-DERATE design contrast.

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.