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

In summary, the source of most of the ADR and IR data recorded by the FDR couldvary. Table 8 provides a summary of the sources for the occurrence flight, based onthe actual FDR data (discussed below).Table 8: FDR’s source of ADR and IR parameters (except AOA)TimeAIR DATAswitchpositionSource ofADR dataATT HDGswitchpositionSource of IRdataTakeoff to 0440:28 NORM ADR 1 NORM IR 10440:28 to 0441:37 NORM ADR 1/ADR 2 NORM IR 20441:37 to 0443:45 NORM ADR 1 NORM IR 20443:45 to 0506:48 NORM ADR 1 CAPT ON 3 IR 30506:48 to landing NORM ADR 1/ADR 2 CAPT ON 3 IR 3Summary of ADR data for the occurrence flight (from the FDR)Soon after 0440:26, spikes became evident on all of the recorded ADR parametersfrom ADIRU 1 (Figure 19). The recorded spikes occurred at different times foreach parameter, and the spikes for many of the parameters contained repetitions of asmall number of values. As the data output rate of the ADIRUs was much higherthan the recording rate of the FDR 50 , the data available to the investigation wasincomplete, and it was not possible to determine the full nature, magnitude andfrequency of the data spikes. Further discussion of the data-spike characteristics isprovided in section 3.3.From 0440:41 to 0441:37, the ADR 1 Fail parameter intermittently recorded a failvalue (Figure 20), which indicated that at least one of the ADR 1 parameters (eitherstandard altitude or computed airspeed) was flagged as invalid during this period.From 0441:38 to 0506:48, the ADR 1 Fail parameter did not record any failindications; however, the FDR recorded many spikes in all recorded ADRparameters (including standard altitude and computed airspeed) during that time.Consequently, because no source switching had occurred, it was evident thatADIRU 1 had transmitted data spikes to other systems as valid data.The FDR did not record any fail values for ADR 2 or ADR 3.50As examples, the ADIRU outputted Mach eight times per second and the FDR recorded it onceper second, and the ADIRU outputted pitch attitude 50 times per second and the FDR recorded itfour times per second.- 36 -