Refuelling

Pressure refuelling is the fuel system's busiest ground operation, and the A330 runs it almost entirely by computer: the operator presets a total, the FCMS distributes it across the tanks in the correct and safe configuration, tests its own overfill protection first, and shuts everything when done. This article follows the fuel from the coupling to the tanks, then works through the automatic sequence, the protections behind it, manual and overwing fallbacks, and the handful of numbers a pilot should hold (25/35 minutes, 200 kg, 3 000 kg, THS at zero).

1. The plumbing — coupling to diffuser

 fuel bowser hoses (50 psi / 3.45 bar)
        │
 [REFUEL/DEFUEL COUPLING] — under the wing leading edge;
        │                    two valve heads per coupling
 [ISOLATION VALVE] — electrically controlled, HYDRAULICALLY operated
        │            (opens only when energised AND pressure present);
        │            manual override button on the valve body
        ▼
 ═══ REFUEL GALLERY ═══ runs the wing span
   │      │      │      │
 [inlet valves per tank: outer M/N · inner F/H · centre G · trim L]
   │
 [restrictor valves: centre 5515QA · trim 5506QA — flow/pressure limiters]
   │
 [REFUEL DIFFUSERS] — slow the fuel into the tank (anti-static, anti-splash)

Aircraft are fitted with either one or two couplings; each coupling carries two valve heads, so up to four hoses can feed simultaneously on two-coupling aircraft. Time from usual reserves to full at 50 psi: approximately 25 minutes with four hoses, 35 minutes with two.

Details that earn their keep:

• the isolation valve is electro-hydraulic — solenoid energised and refuel pressure present, then it opens; no pressure, no flow regardless of electrics. If the solenoid side fails, a manual override button on the valve still opens it mechanically — refuelling survives an electrical fault;
• battery-only refuelling is supported: "It is possible to use only the electrical power from the aircraft batteries to do a refuel of the aircraft";
• the trim restrictor valve limits flow and pressure toward the trim tank but lets fuel return freely the other way — the THS tank is protected from being slammed, never from being drained;
• static safety: refuel bonding points are provided on each main-gear uplock pin.

Attitude matters more than expected: to reach full tanks the aircraft must be on level ground with the THS at 0°; refuelling is possible on slopes up to 2° or with THS between −1° and +5°, but maximum capacity is then unobtainable — the trim tank lives inside the stabiliser, so the stabiliser's angle changes how much it can hold.

2. The automatic sequence

At the refuel/defuel panel (990VU, behind its quick-release door — opening the door itself powers the panel circuits and tells the FCMS):

1. Preselect the total with the LOAD/INC/DEC switch — the PRESELECTED figure must exceed ACTUAL;
2. MODE SELECT to REFUEL — the isolation valves are energised; flow starts when the bowser pressurises;
3. HI LEVEL TEST first — the test pushbutton makes the FCMS run a continuity check of every high-level and overflow sensor: serviceable circuits answer by toggling their panel lights (lights that were off come on, lights that were on go off), and during the test the FCMS drives all inlet valves closed. Refuelling proper begins only after the overfill protection has proven itself;
4. The FCMS distributes — "automatically distributes the set quantity of fuel in the correct (and safe) fuel tank configuration": outers and inners first, centre as needed, trim per the CG plan, with the trim line's own guard (flow to the trim tank above 450 litres/min is stopped);
5. END light steady = complete; MODE SELECT OFF closes the isolation valves.

Each tank's inlet valve closes on the first of: its two high-level sensors wetting (and once closed for high level it stays closed, even if a sensor later dries), its panel switch set to SHUT, or its tank reaching the allocated load.

APU running during refuel? Covered automatically: if gallery pressure sags while the trim tank is being filled, the low-pressure switch (53QU) isolates the trim line (trim-pipe isolation, trim inlet, trim-tank isolation and auxiliary forward-transfer valves all close) and the APU feeds from its forward pump — see APU fuel feed.

Quality-control numbers at the end:

• wings differing by more than 3 000 kg → END light flashes and the ECAM flags a wing imbalance (FUEL-page quantities flash);
• ACTUAL vs PRESELECTED differing by more than 200 kg (10 s after completion) → one further top-up is permitted; still outside → END flashes.

The stop list. The isolation valves close and refuelling halts if: a surge-tank overflow sensor wets · (six-tank) the centre high-level sensors wet · (jettison-fit) a jettison valve is open or unreporting · any high-level sensor fails · the OUTR TK XFR or T TANK MODE pushbutton is set on in the cockpit. That last one surprises people: someone touching the transfer buttons on the flight deck stops the bowser outside. Fix the condition and the refuel resumes.

[!warning]- Buttons behave differently mid-automatic-refuel A tank switch moved to SHUT acts immediately. Moved to OPEN, it is ignored until the automatic refuel completes — then, about 15 seconds later, refuelling resumes into that tank in manual mode. The automation finishes its job before honouring your request.

3. Manual pressure refuel — the guarded fallback

With MODE SELECT in REFUEL and individual tank switches OPEN, the operator distributes fuel manually; the FCMS still closes valves on wet high-level sensors. Two guards persist:

• the trim tank's longitudinal-balance interlock — its inlet valve will not open unless one of: both inners above 14 000 kg; one inner above 14 000 kg and the other inner's inlet open; (six-tank) the centre inlet open; both inner inlets open. And categorically: "the FCMS does not permit a refuel to the trim tank if it puts the CG of the aircraft into a dangerous condition" — you cannot manually load the tail of an empty aircraft;
• the same stop list as automatic mode (overflow, sensor failure, cockpit transfer buttons).

Manual mode is also the legal fallback for two specific failures: a failed surge-tank overflow sensor, or a jettison valve reported "failed unknown" — both of which block the automatic mode through its stop list.

Cockpit refuel (option): aircraft with the cockpit REFUEL pushbutton preselect via the MCDU; the panel shows CKPT while the cockpit holds control, and a ready-to-refuel light at the coupling tells the ground crew the aircraft is armed.

4. Overwing refuel — the gravity fallback

No pressure source available? Each inner tank has an overwing adapter under a cap on the upper wing surface:

"The fuel only goes into the inner tank. Then it is necessary to do a ground fuel transfer to get the fuel into the correct fuel-load configuration."

Gravity fills the inners only; distribution to other tanks is then a ground-transfer exercise (defuelling and ground transfer) — typically followed by topping the inners up again.

5. After refuelling — the flight-deck face

Two EWD memos police the panel state (controls and ECAM): REFUEL PNL DOOR OPEN-family logic shows when the door is open or any panel control is out of the flight position (MODE SELECT not OFF, a valve switch out of NORM, the transfer switch OPEN, power on BAT) — the pre-departure check is, in essence, every switch back, door closed. On the dispatch side, the MEL's alert-to-item mapping makes "REFUEL IN PROCESS displayed" one of the fastest tables to consult after an abnormal refuel.

Self-test

[!note]- Q1. Why does the HI LEVEL TEST come before fuel flows — and what does a healthy circuit look like? The test proves the overfill protection (high-level and overflow sensors) before it is needed; serviceable circuits toggle their lights (off→on, on→off) while the FCMS holds all inlet valves closed.

[!note]- Q2. The bowser stops mid-refuel and END flashes. Name three cockpit-side causes. OUTR TK XFR or T TANK MODE set on; (with the list's other members: an overflow sensor wetting, a high-level sensor failure, centre high-level wet on six-tank aircraft, a jettison valve open/unreporting on jettison aircraft).

[!note]- Q3. What stands between a nearly empty aircraft and fuel loaded into its trim tank manually? The longitudinal-balance interlock: trim inlet opens only with inners above 14 000 kg (or equivalent inlet-open conditions) — and the FCMS refuses any trim refuel that would put the CG in a dangerous condition.

[!note]- Q4. Why can't you always reach maximum fuel capacity on a sloping stand? Full capacity requires level ground and THS at 0°; up to 2° slope or THS −1° to +5° still permits refuelling but not maximum capacity — the trim tank's geometry moves with the stabiliser.

[!note]- Q5. What is the 200 kg rule at completion? If ACTUAL differs from PRESELECTED by more than 200 kg ten seconds after completion, one more top-up may be made; if still outside, the END light flashes — the panel's accuracy contract.

Key takeaways

References

• AMM 28-25-00 Description and Operation §3/§6/§7.A (plumbing, isolation valve, automatic and manual sequences, stop lists, interlocks, timings, attitude conditions).
• FCOM DSC-28-10-110 (refuel panel and sequence, pilot level).
• Some operators' MEL ME-28 mapping (alert-to-item table).
• Framing remarks (the "automation finishes first" note) are integrative synthesis.

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.