In-flight upset - 154 km west of Learmonth, WA, 7 October 2008,

Summary of ADR and IR data for the occurrence flight (from the QAR)The QAR data showed that the flight was uneventful until 0440:26 when spikesbecame evident on all of the recorded ADR and IR parameters from ADIRU 1. Thedata spikes continued until the aircraft landed. The QAR data for several keyADIRU parameters are shown in Figure 21. As indicated, frequent spikes wererecorded in IR parameters, and intermittent spikes were recorded for ADRparameters.When there were no spikes, the ADR parameters appeared to be correct. In additionto the data spikes, all of the IR parameters showed persistent deviations from theirexpected values. For most of these parameters, the deviations showed oscillatorybehaviour (Figure 22). The groundspeed parameter showed a differentcharacteristic, gradually diverging from the actual value and increasing to 1,000 kts,where the value remained for the rest of the flight, except for a number of lowervaluedata spikes.A comparison between the overall FDR and QAR data patterns found:• The presence of spikes for all ADR parameters on both the FDR and QARthroughout the flight after 0440:26, indicating that ADIRU 1 flagged most of itsADR output data (including the data spikes) as valid.• The presence of spikes for all IR parameters on the QAR but not the FDR duringthe period from 0440:26 to 0443:45 (when the ATT HDG switch position waschanged), indicating that ADIRU 1 flagged most of its IR output data as invalid.Figure 21: QAR plot showing key ADIRU parameters- 39 -