On 15 April 2012, a Virgin Australia, Boeing 737-8FE aircraft, registered VH-VOL departed Gold Coast, Queensland on a scheduled flight to Melbourne, Victoria.
During climb, the crew observed that both engines were being supplied only from the right fuel tank. This resulted in a fuel quantity difference between the left and right fuel tanks. The crew conducted the fuel leak engine checklist which confirmed that no engine fuel leak existed. With centre tank fuel available, the crew selected the centre tank pumps on, which resulted in the fuel imbalance stabilising.
Given that the crew were unable to confirm fuel from the left tank could be used once the centre tank pumps were selected off, or that no fuel leak existed, they elected to divert to Brisbane, Queensland and declare a PAN. The aircraft landed without further incident.
An overhaul organisation inspected the engine fuel feed crossfeed valve and identified wear to the sealing materials and Teflon within the valve body as consistent with the existence of a leak within the valve. However, the overhaul organisation was unable to confirm whether the sealing material degradation would explain a high volume fuel leakage rate.
Virgin Australia Airlines had previously established an inspection program for the crossfeed valves in accordance with Boeing recommendations. The operator also has a program in place to replace existing crossfeed valves with a modified version at scheduled maintenance servicing. This program is currently under review for acceleration.