C7/2010L Airliner fuel system malfunction: incident during an approach to Helsinki-Vantaa aerodrome on 5 July 2010

The incident occurred on 5 July 2010 on Finnish Commuter Airlines Oy scheduled flight FCM256K from Kuopio to Helsinki-Vantaa. The aircraft was an ATR 72, registration OH-ATK. There were 18 passengers and four crew members onboard. When the aircraft landed at Helsinki-Vantaa aerodrome its right main fuel tank was almost empty.

Accident Investigation Board of Finland (AIB) classified this occurrence as an incident. On 8 July 2010 it appointed investigation commission C7/2010L for this incident. The investigation revealed that during the pre-flight checks the electrical pump in the left main tank was found to be broken. Nevertheless, it was permissible to fly the flight in accordance with the instructions of the Minimum Equipment List (MEL). The mechanic that was summoned to the aircraft advised the pilots to keep the fuel crossfeed valve open at all times. The pilots took this as a recommendation to keep the cross-feed on during the entire flight. This was an erroneous notion, which the pilots did not double-check from their own MEL.

Due to the fuel system malfunction and the incorrect fuel feed selections both engines received fuel only from the right main tank. The return leg from Kuopio to Helsinki was flown with analogous fuel feed selections. The aircraft was not refuelled in Kuopio. When the aircraft was parked at Helsinki-Vantaa aerodrome the right main tank gauge indicated zero fuel. The occurrence did not result in any injuries to persons or damage to equipment. As a result of the situation an emergency alert was issued at Helsinki-Vantaa.

The investigation also established whether both engines would have flamed out if the right main tank had emptied. According to the aircraft manufacturer’s (ATR) comments, in such a case the left main tank would have continued to supply fuel to both engines and they would not have flamed out.

The basic cause of the occurrence was that the pilots failed to complete their MEL and the Dispatch Deviation Guide (DDG) at both Helsinki-Vantaa and Kuopio. Rather, they relied on the mechanic’s missunderstood advice.

Another cause was that the pilots did not determine the reason for the fuel imbalance. They calculated that they had enough fuel for the return flight and, subsequently, did not have the aircraft refuelled. The pilots had an inaccurate notion of how the fuel system functioned.

The third cause was that the pilots did not follow the instructions in the abnormal procedures checklists to land as soon as possible when they noticed the impending fuel shortage.

Contributing factors included the pilots’ limited experience in their present duties and lacking airmanship, the captain’s degraded performance, insufficient Crew Resource Management as well as the uncomfortable work environment caused by the hot weather and the feeling of haste due to the delayed departure.

The investigation commission issued no safety recommendations.

C7/2010L Report (pdf, 0.66 Mt)