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

esult of a problem that was subsequently rectified and was not considered aresult of, or cause of, any electrical continuity or other problems.• The coating on the monitor module circuit board was cracked in one location.The board was tested while undergoing deformation (flexing) and with moistureapplied without any functional effects.• An input discrete (single wire interface) to the monitor module failed a voltagerange test. The discrete was used to identify the aircraft type on which theADIRU would be installed, to disable the ADR part for some aircraft types. Thetest failed by a marginal amount (0.018 V) due to a redesign of the associatedcircuitry.• A power supply diode was found to be cracked. The associated circuitry was notaffected significantly. In flight, failure of this diode would result in a number ofADIRU power supply BITE tests being triggered and the ADIRU shuttingdown.• The power supply BITE circuitry exhibited a fault, which was eventually tracedto a faulty resistor that had passed a check at the beginning of the test. In flight,failure of the resistor would result in the ADIRU shutting down. The problemwas considered to have arisen during the testing.None of the above issues for either unit 4167 or 4122 were considered relevant tothe occurrences under investigation. No other problems were identified.Environmental testsContinuous maintenance test procedure with heat shroudThe maintenance test procedure described above was run continuously in a loopmode for 11 full cycles with the unit covered in a shroud to provide heat stress(Figure E2). The temperature inside the unit reached 56°C with the shroud on.Figure E2: ADIRU undergoing test under heat shroudTestequipmentADIRU underheat shroudMovable testplatform- 248 -