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

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$a947-1 flexplate fracture forward flexible coupling main rotor drive ...$

Figure 46: Service history timeline for units 4122 and 4167- 134 -
3.6 Potential trigger types3.6.1 BackgroundAs discussed in section 3.4.10, the data-spike failure mode involved a disruption ofprocessing activities within the ADIRU’s CPU module. The failure mode was also asoft fault; that is, it ceased to exist after the unit was powered off.Soft faults can be triggered by a range of factors, such as a software corruption or‘bug’, or a hardware anomaly triggered by some form of environmental factor(including physical environment factors, electromagnetic interference, or singleevent effects). Evidence relevant to each of these possibilities is provided in theremainder of this section.None of the effects of the data-spike failure mode were observed until the failuremode was triggered, and the effects recurred continuously until the unit was shutdown. In addition, the failure mode could not be replicated during subsequenttesting using a wide variety of potential triggers, indicating that the failure modecould only be triggered by either a rare event, or under rare circumstances. Thisbehaviour indicated that the disruption to the CPU module’s processing wastriggered by a single event rather than a series of events (that is, it was very unlikelythat a separate event triggered each data spike or other processing problem).3.6.2 SoftwareSoftware ‘bug’A software ‘bug’ is a flaw or mistake in a program that causes it to behave in a waythat was not intended by its designers. Such bugs only manifest themselves under aspecific set of circumstances that produce the same fault each time they occur.However, it may be extremely difficult to reproduce the program state that existedat the time a problem occurred because complex software has a very large numberof data items and functions, all of which interact with each other and most of whichare time-dependent.Overall, if the failure mode was due to a software bug, it would be expected that itwould not reoccur more than once on any given unit without also occurring onmany other units. This was not the case with the LTN-101 data-spike failure mode,where the problem occurred twice on one unit and only once on another unit out ofmore than 8,000 units in operation.Software corruptionThe LTN-101 ADIRU software was stored in ROM. If software corruption were tooccur in this type of memory, it would generally result in a hard fault because theerroneous software would be loaded every time the unit was powered up, and thefault would be reproduced as soon as the corrupted instruction was executed.Nevertheless, software corruption can sometimes affect a system’s behaviour in lessobvious ways, such as if the corruption occurred in a set of instructions that wereonly executed on rare occasions. In such cases the problem would only reoccurwhen those instructions were executed. As discussed in section 1.16.2, there was- 135 -
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ATSB TRANSPORT SAFETY REPORTAviatio
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Published by: Australian Transport
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3 FACTUAL INFORMATION: AIR DATA INE
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DOCUMENT RETRIEVAL INFORMATIONRepor
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TERMINOLOGY USED IN THIS REPORTOccu
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CSMCSSCVRDADSDCDGACDMCDMUEASAECAMED
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RAMRTCASATCOMSAESAOSDSECSEESEUSSASS
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FCPC design limitationAOA is a crit
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associated with a master caution ch
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Figure 2: Aircraft track and key ev
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The crew decided that they needed t
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1.3 Damage to aircraftThere was sig
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• The flight crew provided inputs
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exceeding a predefined safe flight
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Table 1: Examples of ADIRU flight d
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Inertial reference partThe IR part
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ADIRS switching controlsIn normal o
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Processing by ADIRUs and FCPCsEach
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The information presented on the fl
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A system could flag its output data
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Table 4: Summary of indications for
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Figure 17: ECAM engine / warning di
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Table 6: Required actions associate
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For internal aircraft communication
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Table 7: Sequence of events (from t
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In summary, the source of most of t
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Summary of IR data for the occurren
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Figure 22: QAR plot showing oscilla
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QAR dataOverall, the QAR recorded 4
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Flight crew pitch inputsDuring manu
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They provided information for maint
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Table 11: Cockpit effect messages d
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Table 13: Troubleshooting data rela
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position 1 on QPA. Further details
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class 1 fault messages shown in Tab
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If there was a discrepancy between
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1.15 Survival aspectsInformation on
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did not identify any faults. The BI
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Comparison of the three occurrences
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1.17.2 Processes for reporting and
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2 FACTUAL INFORMATION: ELECTRICAL F
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monitored external systems that pro
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Each FCPC used a number of paramete
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AOA computation logicThe FCPC softw
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Figure 29: FCPC processing of sever
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Table 19: Characteristics of elevat
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Simulation of AOA values for the fi
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2.2.2 Review of recorded flight con
Page 103 and 104: second PRIM 3 FAULT. The role of ma
Page 105 and 106: The ACJ was built around the princi
Page 107 and 108: • It stated that the identificati
Page 109 and 110: The second part of the V-cycle invo
Page 111 and 112: • Functional requirements. These
Page 113 and 114: 2.4.5 Safety assessment activitiesG
Page 115 and 116: equipment software and aircraft ins
Page 117 and 118: 2.5.4 Factors associated with the i
Page 119 and 120: it is very difficult if not impossi
Page 121 and 122: applicable to highly-integrated or
Page 123 and 124: Ongoing developmentsA range of rese
Page 125 and 126: To conduct an effective fault tree
Page 127 and 128: According to this model, accidents
Page 129 and 130: 3 FACTUAL INFORMATION: AIR DATA INE
Page 131 and 132: • inertial reference input/output
Page 133 and 134: 3.3 Examination of data-spike patte
Page 135 and 136: Figure 38: ARINC 429 word for an AO
Page 137 and 138: 3.3.4 Data-spike patterns for the 7
Page 139 and 140: Figure 43: Qualitative correlation
Page 141 and 142: etween the values of any of the fou
Page 143 and 144: 3.4.3 Calculating parameter valuesA
Page 145 and 146: 3.4.5 Packaging the ARINC 429 wordT
Page 147 and 148: 3.4.8 Transmitting data to other sy
Page 149 and 150: ARINC 429 packaging analysisThe ADI
Page 151 and 152: component configurations of differe
Page 153: manufacturer reported such BITE dat
Page 157 and 158: such as liquids or small loose frag
Page 159 and 160: wires). The electric 144 field stre
Page 161 and 162: Although the investigation could no
Page 163 and 164: 3.6.6 Single event effectsBackgroun
Page 165 and 166: until a few years ago, were not dir
Page 167 and 168: Unit testingIn 2005, as part of the
Page 169 and 170: that involved a NAV IR and/or NAV A
Page 171 and 172: EMI from other aircraft systems (su
Page 173 and 174: from ADIRU 1 was not correctly reco
Page 175 and 176: • Detected failure. Any failure w
Page 177 and 178: The ADIRU manufacturer’s analysis
Page 179 and 180: the aircraft and ADIRU manufacturer
Page 181 and 182: 4 FACTUAL INFORMATION: CABIN SAFETY
Page 183 and 184: Summary details of the cabin crew
Page 185 and 186: section, and the ninth flight atten
Page 187 and 188: Table 29: Significant cabin communi
Page 189 and 190: Figure 48: Example of damage to the
Page 191 and 192: 4.3.2 Seat belt examinationsSix pas
Page 193 and 194: The flight crew’s procedures requ
Page 195 and 196: takeoff, landing or when the seat-b
Page 197 and 198: Table 31: Levels of injuryInjury le
Page 199 and 200: 4.6.4 Injuries to seated occupants
Page 201 and 202: The percentage of occupants who wer
Page 203 and 204: Statistical analyses 197 were done
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passengers reported that they had h
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that seat belts should be worn only
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4.8.2 Handholds in the cabinThe FAA
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Figure 53: Overview of the 7 Octobe
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process needs to ensure that there
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and determine whether they could le
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useful in this case. If the EFCS sp
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5.3.2 Risk associated with the fail
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• All three events occurred in a
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place. Although aviation manufactur
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equiring cabin crew to enforce the
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With the information available to t
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ADIRU 1 affected the operation of a
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6 FINDINGSFrom the evidence availab
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• As of April 2010, the LTN-101 a
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did not illuminate. The new OEB (A3
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modifications were made to its guid
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this advice. At the time of the fir
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APPENDIX A: VERTICAL ACCELERATIONST
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APPENDIX B: FLIGHT RECORDER INFORMA
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APPENDIX C: POST-FLIGHT REPORTThe f
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APPENDIX D: OTHER DATA-SPIKE OCCURR
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Occurrence on 27 December 2008Overv
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Figure D2: FDR data for the 27 Dece
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ADIRU informationADIRU 1 was the sa
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APPENDIX E: ADIRU TESTINGTest plan
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Visual inspectionsExternal visual i
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(ADR) output databuses. Loading on
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Unit 4167 passed 2,223 of 2,272 tes
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dwells (sustained testing at a fixe
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APPENDIX F: AIRCRAFT LEVEL TESTINGI
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APPENDIX G: ELECTROMAGNETIC RADIATI
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cannot be ‘decoded’ by the rece
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APPENDIX H: SINGLE EVENT EFFECTSNot
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Factors affecting SEE exposureAn ai
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portions of memory are constantly b
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Depending on the form of EDAC, sing
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• crew actions: the passenger’s
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The questionnaire respondents were
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was centred across the passenger’
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Previous occurrencesThe seat belt m
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Australian turbulence eventsThe mos
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APPENDIX L: SEAT BELT USE IN ROAD V
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Table L1: Recent seat belt use rate
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US Federal Aviation AdministrationT
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APPENDIX N: SOURCES AND SUBMISSIONS
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Hanson, RJ 1987, Conducted electrom
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Tvaryanas, AP 2003, ‘Epidemiology
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In-flight upset - 154 km west of Le
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In-flight upset - 154 km west of Learmonth, WA, 7 October 2008,

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