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The Aviation Herald is reporting the European Aviation Safety Agency (EASA) has issued an updated Emergency Airworthiness Directive (EAD) 2009-0012-E following two incidents involving Qantas Airbus A330 and A340.
These incidents were attributed to Air Data Inertial Reference Unit #1 (ADIRU-1) providing erroneous data. The EAD recognizes additional failure modes, that have been discovered in the meantime.
EAD 2009-0012-E : Navigation – Air Data Inertial Reference Unit (ADIRU) – Operational Procedure, requires flight crews of the Airbus A330 and A340, who experience failures by one of the three ADIRUs on board of their aircraft not to limit their actions to turning off the affected ADIRU off, but to completely de-energize it under all circumstances by selecting the IR mode rotary to OFF.
A first EAD 2008-225-E had been issued on December 18th 2008 following an inflight upset of a Qantas Airbus A330-300 near Learmonth on Oct 7th 2008. During this event a faulty ADIRU-1 had transmitted randomly faulty data producing unjustified stall and overspeed warnings prompting the airplane’s systems to pull the airplane into a dive. Disengaging the ADIRU did not stop the faulty ADIRU from transmitting such faulty data. The resulting EAD required the crews to verify, whether the disengagement of the ADIRU was followed by the OFF light to illuminate and in case of this light not appearing to de-energize the ADIRU.
A second incident occured to another Qantas Airbus A330-300 near Perth on December 27th 2008 leading to the disconnection of the autopilot, but without an inflight upset. The emergency directive now suggests, that the crew, following the first version 2008-225-E of the emergency directive received the OFF light for their ADIRU-1, however, the ADIRU-1 still did not disconnect and continued to supply faulty data.
The full Emergency Airworthiness Directive is available here.
