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

Table 9 details the number of spikes for each value recorded by the FDR (see alsosection 3.3.4). 52Table 9: AOA 1 spike details (as recorded by the FDR)Magnitude (°) Number Time of first spike Time of last spike50.625 29 0440:34 0452:3716.875 8 0511:57 0530:225.625 18 0500:32 0531:15Figure 23 shows the AOA spikes recorded by the FDR during the period coveringthe two pitch-downs. Also shown are the recorded stall warnings, which were basedon AOA values, overspeed warnings and master warnings.Only a small number of situations could trigger a master warning, including aninvoluntary (uncommanded) autopilot disconnection, stall, overspeed, engine fire,or a high cabin altitude. The first master warning on the occurrence flight was dueto the involuntary autopilot disconnection while the later master warnings were dueto either stall warnings or overspeed warnings. Although there was a generalcorrelation between the times of the master warnings and the stall or overspeedwarnings, it was not exact. This result was explained by the sampling rates and thecomputation time of the FWS, the sampling rates of the acquisition unit for theFDR, and the brevity of the stall and overspeed warnings.Figure 23: FDR plot showing recorded AOA spikes for both pitch-downs52There were also several instances of invalid AOA 1 data being provided by the ADIRU. When thisoccurred, it was indicated on the FDR with a value of -45° (Appendix B).- 41 -