Fuel contamination, causing the seizure of engine valves, has been identified as the prime suspect after a Cathay Pacific Airbus A330-300 suffered a double powerplant malfunction on approach to Hong Kong four months ago.

The aircraft, operating flight CX780, landed at high speed on 13 April after its left-hand Rolls-Royce Trent 700 engine jammed at a high thrust setting while the right-hand engine remained at low thrust. No evidence has emerged of spurious command signals from the engine controls.

But investigators discovered fine spherical particles - their nature is still to be determined - inside the fuel tanks, fuel system and several engine components, including the fuel metering units and stator vane controls.

Examination of the engine fuel components showed that both engines' main metering valves had jammed in positions consistent with the thrust levels experienced on the approach.

"The abnormal engine performance during the flight was believed to have been caused by stiction, and eventual seizure, of the [valves]," says the Hong Kong Civil Aviation Department, which says that the spherical particles could not have been generated by the aircraft or its engine systems.

While the inquiry has yet to reach any conclusions, suspicion has fallen on the uplifting of 24.4t of fuel to the A330 while it was parked at Surabaya's Juanda International airport. The hydrant refuelling circuit serving 10 stands at the airport had undergone extension work as part of an apron extension project.

"Subsequent investigation at [Juanda airport] noted that some of the recommissioning procedures of that hydrant extension work were not in line with the guidelines and practices commonly used by the aviation fuel industry," says the Civil Aviation Department.

It adds that the refuelling system for several stands, including that used by the A330, was employed before these recommissioning procedures were completed. After the CX780 landing incident the refuelling circuit was isolated.

Although the inquiry is continuing, the Civil Aviation Department is recommending that Juanda airport's authorities review the procedures and ensure they are completed before the refuelling system is brought back into operation.

Source: Flight International