D1/2011L In-flight fuel leak in a passenger aircraft on 15 January 2011

An incident occurred on 15 January 2011 to a Boeing 757-28A twin-engine passenger aircraft, registration OH-AFJ, which was on a scheduled charter flight FIF-661 from Helsinki to Las Palmas. The aircraft was operated by Air Finland Ltd and owned by International Lease Finance Corporation. After about two hours in-flight, the pilots’ fuel monitoring showed that fuel consumption was higher than calculated. On closer examination, the pilots concluded that there was a fuel leak and traced it to the right fuel system or engine. The fuel leak was so large that the captain decided to land at the nearby Paris Charles de Gaulle airport. The incident did not result in injuries to persons or any other damage.

The sequence of events was established through interviews of the parties involved, flight and aircraft documents, and flight data recorder print-outs. The investigation focused on pre-flight maintenance actions, which were examined based on the aircraft maintenance records as well as other documents and evidence provided by the organisations.

The immediate cause of the incident was a fuel leak from a fuel tube coupling in the right engine high pressure fuel pump. The investigation group found three possible causes for the fuel leak.

The most probable cause leading to the fuel leak, as concluded by the investigation group, is that the fitting of the seal was originally too tight, for which reason the seal may have been pressed incorrectly against the edge of the groove when it was installed during maintenance before the incident flight.

Another possible cause for the fuel leak is that the bolts between the coupling flanges had not been tightened up to the instructed final value during maintenance before the incident flight.

The third possible cause for the fuel leak is that a wrong seal was inadvertently installed in the coupling during maintenance before the incident flight. The investigation group does not consider this likely, but it cannot be fully excluded.

The in-flight fuel leak resulted in an incident. The pilots did not shut down the leaking engine during the flight, although the Quick Reference Handbook (QRH) instructs to do so in engine fuel leak situations. The pilots’ deviation from QRH instructions caused the maximum allowable fuel imbalance to be exceeded as the fuel leak continued, which led to operations outside the approved performance envelope and the incident developed into a serious incident according to ICAO classification.

The Safety Investigation Authority, Finland will not issue any safety recommendations. Originally, it intended to issue four safety recommendations to Air Finland Ltd, but since the company was placed into liquidation during the investigation, any recommendations can no longer be directed to the airline.

D1/2011L Report (pdf, 0.37 Mt)