Virgin Australia Airlines is reviewing their program to replace engine fuel feed crossfeed valves after a fuel imbalance on a flight from Gold Coast to Melbourne led to a declaration of a PAN and a diversion to Brisbane.
During climb, the crew observed that both engines were being supplied only from the right fuel tank, resulting 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.
Since the crew could not confirm fuel from the left tank could be used once the centre tank pumps were selected off, or that no fuel leak existed, they diverted to Brisbane. 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.
...the crew selected the centre tank pumps on, which resulted in the fuel imbalance stabilising.
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.
You can find this and other investigations in the ATSB’s Aviation Short Investigation Bulletin issue 13. The bulletin highlights valuable safety lessons for pilots, operators and safety managers.
Read the report: Fuel imbalance - Boeing 737, VH-VOL, 28 km south-west of Gold Coast Airport, Queensland, on 15 April 2012, which includes important advice.