Crossfeed

One valve sits in the gallery between the left and right engine-feed lines. Closed — the normal state — it cuts the fuel system into two independent halves. Open, it turns six pumps and two tanks into a single pool from which any pump can feed any engine. Almost every fuel abnormal ends up asking the same question: is the crossfeed your rescue, or your enemy? This article gives the hardware and the decision logic.

1. Hardware — one valve, two motors

The crossfeed valve is a single ball valve driven by two electric motors on separate buses (one of them on the essential side), either motor sufficient — the same dual-actuation pattern as the LP and SPLIT valves, because a valve that reconfigures engine feed must not be lost to a single electrical failure.

Control is the X FEED pushbutton on the overhead FUEL panel:

• pressed in → ON light (blue) in the button, valve drives open; when fully open the OPEN light shows;
• on the EWD, an open crossfeed shows the green memo FUEL X FEED — a deliberate "you have an abnormal configuration set" reminder sitting in the corner of every scan;
• on the SD FUEL page the valve shows in-line green (open) / crossline green (closed) / amber when position and command disagree.

Position-versus-command disagreement raises FUEL WING X FEED FAULT: stuck open → monitor for slow imbalance; stuck closed → the imbalance procedure's backup path exists for exactly this case (below).

2. When to open it

Three families of use, all crew-initiated (the FCMS never opens it):

1. Fuel imbalance — feed both engines from the heavy side until balanced (fuel imbalance);
2. Engine-out — burn the dead engine's fuel through the live engine, simultaneously solving fuel access and the slow imbalance an engine-out creates;
3. Pump-group loss on one side (no leak) — the WING PUMPS LO PR procedure's first action: the healthy side's pumps push fuel across to the starving engine (pump failures and gravity feed).

If the valve is failed closed when imbalance correction is needed, the QRH provides the gallery detour: open OUTR TK XFR to connect the two inner tanks through the refuel gallery, then fly a small sideslip (3° wing-down on the lighter side, rudder for heading, stick neutral) to move fuel by gravity — slow but functional (fuel imbalance).

3. When it must stay shut

The crossfeed shares one pool — which is exactly wrong when one side's fuel or plumbing is the problem:

[!warning]- Three hard prohibitions

1. FUEL ENG 1(2) FEEDLINE BURST — the procedure's line is WING X FEED — DO NOT OPEN: opening would pump the healthy side's fuel into the ruptured line and overboard.
2. Engine fuel contamination confirmed — WING X FEED — OFF / DO NOT OPEN: keep each engine drinking its own tank; never give contaminated fuel a path to the second engine (fuel contamination).
3. Fuel leak not yet located — the leak procedure holds the crossfeed closed during the isolation test (and the imbalance procedure's first caution diverts you to the leak drill): an open crossfeed feeds the leak from both tanks and destroys the quantity bookkeeping that locates it (fuel leak).

Common thread: open the valve only once you know why the sides differ.

4. Dispatch

Some operators' MEL requires the crossfeed valve operative for dispatch in the general case, and treats its position indication with the same "the light is part of the function" logic as the LP valve — several relief items elsewhere in the fuel chapter (for example the centre-tank burst-disk item in tank venting) explicitly require a check that the crossfeed indication works before dispatch, because their fallback plans depend on it.

Self-test

[!note]- Q1. What is the crossfeed's normal position, and who can open it? Closed — the system flies as two independent halves. Only the crew opens it (X FEED pushbutton); the FCMS has no authority over it.

[!note]- Q2. How do you know the crossfeed is open from the EWD alone? The green memo FUEL X FEED is displayed whenever the valve is open.

[!note]- Q3. An imbalance needs correcting but the crossfeed is failed closed. What is the backup? Connect the inner tanks through the refuel gallery (OUTR TK XFR ON) and fly a small sideslip — 3° wing-down toward the lighter side, rudder holds heading — to move fuel by gravity.

[!note]- Q4. Name the three cases where opening the crossfeed is prohibited. Feedline burst (would feed the rupture), confirmed fuel contamination (would poison the second engine), and an unlocated leak (would feed the leak from both sides and wreck the isolation logic).

[!note]- Q5. Why does an engine-out usually lead to crossfeed use? The dead engine stops burning its side's fuel — both an access problem (fuel you cannot use) and a growing imbalance. Feeding the live engine from the dead side solves both.

Key takeaways

References

• FCOM DSC-28-10-40 (crossfeed valve, control and indication); PRO-ABN-FUEL (FEEDLINE BURST, WING PUMPS LO PR, X FEED FAULT); QRH fuel imbalance / fuel leak procedures.
• AMM 28-23-00 (valve hardware).
• Some operators' MEL (valve and indication requirements).
• The "rescue or enemy" framing is 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.