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Somebody correct me if I'm reading this wrong, but it appears with a bad IRU telling the airplane it is in a stall, the fly by wire takes over and the crew has no control over the jet. In this case, the jet did a negative G push over injuring passengers. In August 2005 a 777 did a pitch up for similar reasons. The answer apparently is to get the IRU and any system that allows the bad IRU to communicate with the others (in this case the Air Data Inertial Reference Unit) OFF, ASAP.
Source: Australian Air Transport Safety Board
... .
The aircraft was flying at FL 370 or 37, 000 feet with Autopilot and Auto-thrust system engaged, when an Inertial Reference System fault occurred within the Number-1 Air Data Inertial Reference Unit (ADIRU 1), which resulted in the Autopilot automatically disconnecting. From this moment, the crew flew the aircraft manually to the end of the flight, except for a short duration of a few seconds, when the Autopilot was reengaged. However, it is important to note that in fly by wire aircraft such as the Airbus, even when being flown with the Autopilot off, in normal operation, the aircrafts flight control computers will still command control surfaces to protect the aircraft from unsafe conditions such as a stall.
The faulty Air Data Inertial Reference Unit continued to feed erroneous and spike values for various aircraft parameters to the aircrafts Flight Control Primary Computers which led to several consequences including:
The Digital Flight Data Recorder data show that ADIRU 1 continued to generate random spikes and a second nose-down aircraft movement was encountered later on, but with less significant values in terms of aircraft's trajectory.
At this stage of the investigation, the analysis of available data indicates that the ADIRU 1 abnormal behaviour is likely as the origin of the event.
The aircraft contains very sophisticated and highly reliable systems. As far as we can understand, this appears to be a unique event and Airbus has advised that it is not aware of any similar event over the many years of operation of the Airbus.
Airbus has this evening, Australian time, issued an Operators Information Telex reflecting the above information. The telex also foreshadows the issue of Operational Engineering Bulletins and provides information relating to operational recommendations to operators of A330 and A340 aircraft fitted with the type of ADIRU fitted to the accident aircraft. Those recommended practices are aimed at minimising risk in the unlikely event of a similar occurrence. That includes guidance and checklists for crew response in the event of an Inertial Reference System failure.
Meanwhile, the ATSB's investigation is ongoing and will include:
20 "Serious" injuries, cabin panels smashed, etc:
http://www.smh.com.au/articles/2008/10/08/1223145446448.html?feed=html
Source: Australian Air Transport Safety Board
... .
The aircraft was flying at FL 370 or 37, 000 feet with Autopilot and Auto-thrust system engaged, when an Inertial Reference System fault occurred within the Number-1 Air Data Inertial Reference Unit (ADIRU 1), which resulted in the Autopilot automatically disconnecting. From this moment, the crew flew the aircraft manually to the end of the flight, except for a short duration of a few seconds, when the Autopilot was reengaged. However, it is important to note that in fly by wire aircraft such as the Airbus, even when being flown with the Autopilot off, in normal operation, the aircrafts flight control computers will still command control surfaces to protect the aircraft from unsafe conditions such as a stall.
The faulty Air Data Inertial Reference Unit continued to feed erroneous and spike values for various aircraft parameters to the aircrafts Flight Control Primary Computers which led to several consequences including:
- false stall and overspeed warnings
- loss of attitude information on the Captain's Primary Flight Display
- several Electronic Centralised Aircraft Monitoring system warnings.
- the flight control computers commanding a nose-down aircraft movement, which resulted in the aircraft pitching down to a maximum of about 8.5 degrees,
- the triggering of a Flight Control Primary Computer pitch fault.
The Digital Flight Data Recorder data show that ADIRU 1 continued to generate random spikes and a second nose-down aircraft movement was encountered later on, but with less significant values in terms of aircraft's trajectory.
At this stage of the investigation, the analysis of available data indicates that the ADIRU 1 abnormal behaviour is likely as the origin of the event.
The aircraft contains very sophisticated and highly reliable systems. As far as we can understand, this appears to be a unique event and Airbus has advised that it is not aware of any similar event over the many years of operation of the Airbus.
Airbus has this evening, Australian time, issued an Operators Information Telex reflecting the above information. The telex also foreshadows the issue of Operational Engineering Bulletins and provides information relating to operational recommendations to operators of A330 and A340 aircraft fitted with the type of ADIRU fitted to the accident aircraft. Those recommended practices are aimed at minimising risk in the unlikely event of a similar occurrence. That includes guidance and checklists for crew response in the event of an Inertial Reference System failure.
Meanwhile, the ATSB's investigation is ongoing and will include:
- Download of data from the aircraft's three ADIRUs and detailed examination and analysis of that data. Arrangements are currently being made for the units to be sent to the component manufacturer's facilities in the US as soon as possible and for ATSB investigators to attend and help with that testing, along with representatives from the US National Transportation Safety Board, The French Bureau dEnquêtes et dAnalyses (BEA) and Airbus.
- In addition, investigators have been conducting a detailed review of the aircraft's maintenance history, including checking on compliance with relevant Airworthiness Directives, although initial indications are that the aircraft met the relevant airworthiness requirements.
- Work is also ongoing to progress interviews, which will include with injured passengers to understand what occurred in the aircraft cabin. The ATSB plans to distribute a survey to all passengers.
20 "Serious" injuries, cabin panels smashed, etc:
http://www.smh.com.au/articles/2008/10/08/1223145446448.html?feed=html
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