Emergency update – The French BEA ( Bureau of Enquiry and Analysis for Civil Aviation Safety) have updated on the systematic failure of navigation equipment on XL Airways A330-200 from 26th December 2014.
The specific navigation system in question was the ‘Inertial Reference System’ which is made up of 3 independent systems in the A330 – IRS1, IRS2 & IRS3. While on the ground at ‘Roland Garros Airport’ in Reunion just east of Madagascar one of these systems (IRS2) reported a deviation in location between 6-15nm, while this is unusual the other two ‘IRS’ still in operation act as a redundancy.
The faulty system on the aircraft was due to be replaced 2 days earlier but due to an identification mistake the wrong IRS was replaced and subsequently the faulty device started a cascade of events that resulted in a loss of primary flight information and other autopilot systems on the aircraft such as the auto-throttle.
For some reason the crew switched IRS3 to ‘attitude’ from its original setting of ‘navigation’ then the flight-guidance computer reverted back to using IRS1 & IRS2, IRS2 being the faulty equipment.
The conflicting information between the 2 systems prompted a disengagement of the autopilot, autothrust and flight directors, and the disappearance of position and flightplan information on the navigation displays.
The crew had to determine their position via a back-up navigation system and re-align all 3 IRS mid-flight. Since the navigation system was not operating as it should, the TCAS (Traffic Collision Avoidance System) went offline and the crew had to declare an emergency and squawk 7700.
Air Traffic Control vectored the aircraft to Athens and the crew successfully landed the A330 manually.