What happened
On 24 April 2025, a Boeing 737-8200 MAX, registration EI-HEZ, was operating a passenger flight from Venice to Manchester. Shortly after reaching cruise altitude, the crew noticed a fuel imbalance between the wing tanks. The commander performed a fuel balancing procedure from memory, but a second imbalance was identified approximately 20 minutes later.
Upon reviewing the fuel consumption, the crew determined that the imbalance was increasing at a rate that suggested an engine fuel leak. Although the Quick Reference Handbook (QRH) specifies a threshold for identifying a leak, the pilots noted the rate was only slightly above this limit. Consequently, the crew decided to divert to London Stan and elected not to shut down the affected engine, stopping the non-normal checklist prematurely.
During the approach to Stansted, the 'IMBAL' alert illuminated. Following landing, the aircraft was met by the fire service, who confirmed fuel was leaking from the right engine. There were no injuries and no fatalities among the 191 passengers or 6 crew members, and no damage was reported to the aircraft.
The investigation
The investigation focused on the crew's decision-making regarding fuel balancing and the management of the suspected leak. Investigators examined the use of the fuel balancing procedure from memory and the decision to bypass the engine shutdown instructions in the QRH. The investigation also looked into the operational risks of using thrust reversers during an active fuel leak.
Findings
- The crew performed the initial fuel balancing procedure from memory, which caused them to miss the instruction to check for a potential leak, thereby delaying the diagnosis of the issue.
- The pilots identified a fuel leak but did not complete the required non-normal checklist to shut down the engine.
- The use of thrust reversers for approximately six seconds during landing increased the risk of fire, as the process can disperse fuel vapour over hot engine components.