Tiger Airways Australia has revised its incident reporting procedures, after Australian authorities found that the airline failed to report a fault on an Airbus A320 aircraft that resulted in a flight diversion months later.
The fault, which involved the A320's aileron control system, caused abnormal vibrations of the aircraft on a flight from Mackay to Melbourne on 18 May 2009. The aircraft, registration VH-VNC, was diverted to Gold Coast and landed safely.
Investigations revealed that the aircraft had experienced a similar problem eight months before the incident, but Tiger did not report it as required, says the Australian Transport Safety Bureau (ATSB). In the earlier incident, the aircraft had to return to its point of origin.
In the May 2009 incident, the aircraft was cruising at flight level 350 when the flight crew experienced a "light continuous shaking", says the ATSB report.
Checks by the pilot showed that the Elevator Aileron Computer (ELAC) 1 system had malfunctioned, which resulted in the ELAC 2 system taking over control of the ailerons.
The aircraft's co-pilot, who looked out of the cockpit window, reported that "the left aileron was moving up and down continuously, and that the left wing was moving up and down through about 1m", says the ATSB report.
The flight crew then decided to divert the aircraft to Gold Coast.
Investigations into the incident found that it was caused by two separate faults in the aircraft's aileron control system.
The servo valve within the aircraft's left green aileron servo was incorrectly adjusted during manufacture, which resulted in "abnormal wear of a number of components within the servo valve".
This particular valve was activated when the aircraft's ELAC 1 system malfunctioned, resulting in the ELAC 2 system taking control of the ailerons, says the ATSB.
The ELAC 2 system controls the left green aileron salvo and the right blue aileron servo, while the ELAC 1 system controls the left blue aileron servo and the right green aileron servo. Only one servo on each side operates at any one time.
To address the fault, the servo valve manufacturer has taken steps to prevent the risk of incorrect adjustment during the manufacturing process, says the ATSB.
In response to the incident, Tiger has "improved the training of its staff and the reportable event requirements in its safety management system manual in an effort to address the non-reporting risk", it adds.
The airline also subsequently incorporated a non-mandatory Airbus service bulletin upgrade on its entire A320 fleet to prevent similar faults.
Source: Air Transport Intelligence news
