Contaminated fuel caused the accident last year in which a Cathay Pacific jet's engines failed forcing the aircraft to make an emergency landing in Hong Kong, investigators confirmed yesterday.
An updated report from the Civil Aviation Department into the incident nine months ago said particles found in the Airbus A330's engines were consistent with those found in the fuelling dispenser at Juanda International Airport in Indonesia.
The report also found similar particles in an engine of another Airbus on the same Cathay Pacific route, which had refuelled at the same stand a day before the accident.
In August, the department said 'fine particles' were found inside both engines of the jet. Investigators said the particles could not have come from within the aircraft airframe or engine systems under normal operating conditions.
The update said the 'fine spherical particles' that caused the engines to fail were five to 20 microns in size, and some as big as 30 microns were also found in the fuel system. One micron is equal to one-millionth of a metre.
'Analysis showed that the spheres contained carbon, oxygen, sodium, chlorine and sulphur and were mainly sodium polyacrylate, which was consistent with the super absorbent polymer material used in the filter monitors on a fuelling dispenser,' the report said.
'Such spheres were also present in the hose and strainer of the dispenser used for refuelling the accident flight at Juanda International Airport ... such contamination was believed to be related to the fuel ... through the dispenser. The investigation so far is not able to establish how the spheres were created and how they could enter the aircraft.'
The report also noted that a filter monitor attached to the fuel stand that the accident jet used collapsed and lax procedures in refuelling operations also contributed to the contamination. They were: weekly monitoring of dispenser pressure was not done properly, staff did not investigate irregularities such as vibration of hoses; and low flow rates well below the required capacity, reducing the effectiveness of monitoring pressure.
The department said although the findings were tentative, the International Civil Aviation Organisation should 'establish requirements for oversight and quality control on aviation fuel supply at airports'.
'Such requirements should also cover the refuel operational procedures and associated training for relevant personnel,' the report said.
Flight CX780 from Surabaya, with 309 passengers and 13 crew on board, made an emergency landing at Chek Lap Kok at 1.43pm on April 13 last year, after engine problems.
The hard landing left all four tyres on the left of the aircraft and two tyres on the right deflated and on fire - probably because of overheating during emergency braking. All on board were evacuated, but eight passengers were injured.
Cathay endorsed the department's recommendations.