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

Figure 22: QAR plot showing oscillations in IR parameters1.11.4 Recorded angle of attack dataFDR dataThe FDR recorded both AOA 1 and AOA 2 values once per second. The ADIRUtransmitted corrected AOA data16 times per second but the FDR only sampled itonce per second. As a result, it was not possible to determine the nature, magnitudeand frequency of all the erroneous AOA data transmitted by the ADIRU. However,no spikes or problems were evident at any time for AOA 2.As the captain’s AIR DATA switch remained set to the NORM position, the sourceof AOA 1 data was always ADR 1. Key results for the AOA 1 data were as follows:• The FDR recorded 42 AOA 1 spikes during the period from 0440:26 until theaircraft landed at Learmonth.• The first AOA 1 spike occurred at 0440:34. AOA 1 values changed from 2.1° to50.625° and back to 2.1° over three successive (1-second) samples.• One of the recorded AOA spikes occurred at 0442:26, immediately prior to thefirst pitch-down (0442:27). The AOA value was 50.625°.• Another of the recorded AOA spikes occurred at 0445:08, immediately prior tothe second pitch-down (0445:09). The AOA value was 50.625°.• Most of the AOA spikes that were recorded by the FDR were 50.625° inmagnitude and occurred during the initial 12 minutes after the first spike. Twoother values (16.875° and 5.625°) were recorded later in the flight.- 40 -