What happened
On January 15, 2011, an Air Finland Boeing 757-28A, registration OH-AFJ, was operating a scheduled charter flight from Helsinki to Las Palmas. Approximately two hours into the flight, the flight crew noticed that fuel consumption was significantly higher than planned. Upon closer monitoring, the crew identified a fuel leak affecting the right-hand engine or its fuel system.
The leak was severe enough that the captain decided to divert to Paris Charles de Gaulle Airport. During the flight, the fuel imbalance between the wing tanks grew to over 885 kg, triggering a 'Fuel Config' warning. Although the Quick Reference Handbook (QRH) instructs the crew to shut down the engine experiencing a fuel leak, the captain elected to keep the right engine running until after touchdown, citing a preference for two-engine performance and concerns regarding vibration in the left engine.
The aircraft landed at Charles de Gaulle at 14:21 UTC. Following the landing, maintenance personnel performed a 'wet motoring' procedure to locate the leak, which was quickly identified. No injuries were reported among the 2/210 crew and passengers, and no damage was sustained by the aircraft.
The investigation
The Finnish Safety Investigation Authority (OTKES) examined the sequence of events, focusing on recent maintenance performed at Helsinki-Vantaa between January 11 and 14, 2011. The investigation reviewed flight data recorder outputs, maintenance records, and interviews with the crew and maintenance personnel. The investigation also looked into the continuing airworthiness management of Air Finland and the oversight provided by Finnair Technical Services.
Findings
- The immediate cause of the fuel leak was a leak at the high-pressure fuel pump fuel line connection on the right-hand engine.
- The leak likely occurred because the seal was improperly seated due to an excessively tight fit, or because the bolts at the flange had not been tightened to the required torque during recent maintenance.
- A contributing factor was the airline's failure to implement a voluntary service bulletin (SB RB.211-73-G230) which would have improved the seal's fit.
- The crew's deviation from the QRH by not shutting down the leaking engine led to a fuel imbalance that exceeded allowable limits, elevating the incident to a serious occurrence under ICAO classification.
- Deficiencies were found in the airline's continuing airworthiness management and the oversight of maintenance work performed by the contractor.