Fuel Transfer Pump

What it's for

A single reversible pump, submerged in the LH tank sump, that can move fuel in either direction between the left and right main tanks through a pipeline routed via the existing intercommunication channel — no new tank wall interfaces. It self-primes in either direction within 10 seconds of power, self-stops once it can't pump any more fuel to the other side, and reports its health to the AMMC.

Two distinct jobs: in OEI, it makes the fuel below the intercommunication channel on the failed engine's side — fuel that would otherwise be stranded and unusable — available to the engine that's still running. In AEO, if the tanks become unbalanced (a leak, uneven consumption, or fuel sloshing during unbalanced flight), it can transfer fuel to restore balance.

The one-way rule in OEI

With one engine failed, the pilot can only transfer fuel from the failed engine's tank to the operating engine's tank — never the other direction. The EDCU FUEL page only shows the button for the failed-engine side; the opposite button is inhibited by software, not just by procedure. This is a hard-wired safeguard against ever pulling fuel away from the engine that's actually keeping the aircraft flying.

Direction and progress show as a green arrow over the FUEL XFER icon on EDCU, PFD and the MFD synoptic page, plus an advisory naming the direction ("FUEL XFER 1→2" or "2→1"). FUEL XFER COMPLETE displays for about 10 seconds once an OEI transfer finishes and the pump stops itself.

Why unusable fuel becomes 0 kg

Without this kit, fuel below the intercommunication channel in the tank tied to a failed engine simply can't reach the system and counts as unusable. With the Fuel Transfer Pump installed and used, that figure becomes 0 kg indicated for OEI — the pump is precisely what closes that gap. Below 160 kg is where this actually starts mattering; above that level the two tanks are already interconnected and balanced on their own.

AEO limits and stopping conditions

In AEO, transfer automatically stops the moment 1(2) FUEL LOW activates on the tank being drawn from — FUEL XFER STOPPED displays for about 10 seconds. In the two genuinely abnormal cases — a leak, or one engine burning fuel unevenly — don't use FUEL XFER unless FUEL LOW is already active on the low tank and the other tank's spare fuel is actually needed to finish the flight safely. The routine case is different: after unbalanced flight has returned to balanced, XFER can simply restore the tanks to even without any of that caution attached. On the ground, it can also be used to correct an unbalance created by single-point refueling below the intercommunication channel.

Pump failure

FUEL XFER PUMP caution: confirm XFER is actually OFF on the EDCU FUEL page. If the fuel on the failed-engine side is needed to finish the flight safely, try switching it back on. If the caution persists, that fuel has to be treated as unusable — land as soon as practicable or as soon as possible, depending on what's actually left.