Occurrence
On November 11, 2013, a Boeing 737-800 was being refueled at Krakow Airport (EPKK). Approximately 10 minutes after refueling began from the right tank, fuel started leaking from the drain-vent system. The refueling operator immediately stopped the process and alerted the airport fire brigade present at the scene. The area was secured until additional fire vehicles arrived to neutralize the fuel spill.
Subsequent Refueling
About three hours later, the fuel supply organization received an order to refuel the same aircraft. Before starting, the refueling vehicle operator informed the new flight crew (the previous crew had been replaced) about the earlier fuel leakage caused by a faulty shut-off valve. The captain then set the aircraft's refueling control panel and explicitly ordered the fuel flow from the tanker to begin. Immediately, fuel again began leaking from the right wing overflow tank. The tanker operator stopped the refueling at once. The airport fire brigade again had to neutralize the fuel spill.
Cause
The incident was caused by a malfunction of the fuel shut-off valve in the aircraft's fuel system, which had been identified during the first refueling but not repaired before the second attempt.
Aftermath
A representative of the aircraft operator was informed of the event and confirmed that, despite the reported defect and without inspection or repair, the aircraft had been scheduled for its next flight.