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

1.15 Survival aspectsInformation on cabin safety matters is provided in Part 4. Of note in this occurrencewas that over 60 passengers were seated but not wearing seat belts, and that theseoccupants had a significantly higher rate of injury than those who were wearingtheir seat belts.1.16 Tests and researchA wide range of tests, examinations and simulations were conducted as part of theinvestigation, as reported in Part 2 (FCPC-related) and Part 3 (ADIRU-related). Thepresent section focuses on a review of potentially-related occurrences.1.16.1 Previous flight control occurrences associated with ADIRUfailuresMost of the systems on modern aircraft are highly reliable. Although equipmentfaults do occur, they rarely have a significant effect on the safety of a flight due tosystem design features such as fault detection and the use of multiple units forredundancy.All models of ADIRUs develop occasional faults, and section 3.9 provides anoverview of faults and reliability associated with the LTN-101 ADIRU. However,it is extremely rare for any ADIRU failures to have an undesirable effect on anaircraft’s flight controls. Airbus advised that it is unaware of any previousoccurrences where an ADIRU failure on one of its aircraft has resulted inundesirable elevator commands.There has been one previous case where an ADIRU failure led to an in-flight upsetof a civilian aircraft. That occurrence involved an ADIRU failure on a Boeing777-200 aircraft, which occurred on 1 August 2005, 240 km north-west of Perth,Western Australia. 70 The ADIRU model used on that aircraft was made by adifferent manufacturer and was of a different system design to the model used onQPA; rather than three separate ADIRUs, the 777 had one ADIRU with redundantcomponents. The aircraft experienced an uncommanded pitch-up, problems withindicated airspeed, and activation of the stall warning and stickshaker devices. Theoccurrence involved hardware failures to two accelerometers within the ADIRU,and inputs from one of the faulty accelerometers being treated as valid data due to asoftware design problem within the ADIRU. The occurrence was unrelated to theoccurrence involving QPA on 7 October 2008.1.16.2 Other ADIRU data-spike occurrencesSearch for other data-spike occurrencesThe ATSB and the operator conducted a detailed review of the operator’smaintenance records for its A330 fleet for events with similar ADIRU behaviour asoccurred on the 7 October 2008 flight. Only one event was identified (12 September70See ATSB investigation report AAIR200503722 available at www.atsb.gov.au.- 58 -