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

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3.2 LTN-101 ADIRU design3.2.1 Design overviewAs noted in section 1.6.4, the LTN-101 contained an air data reference (ADR) partand an inertial reference (IR) part. Overall, the two parts contained seven modulesas shown Figure 36.Figure 36: ADIRU functional architecture (simplified)Further details of the modules are as follows:• air data resolver module, which interfaced directly with the angle of attack(AOA) sensors and total air temperature (TAT) probes• air data input/output module, which interfaced with the external air data modules(ADMs) and the air data resolver module, and sent the final processed ADR datato other systems• sensor electronics module, which provided digital signal processing for theinertial instruments- 110 -
• inertial reference input/output module, which interfaced with the sensorelectronics module, received GPS data, and sent the final processed IR data toother systems• central processor unit (CPU) module, which was the main controlling andprocessing module (section 3.2.2)• monitor module, which provided some basic BITE logic and common discreteinterfaces (such as warning, fail and on/off indications)• power supply module, which converted the aircraft power to the variousvoltages used by the other modules.The ADIRU also contained:• a set of inertial instruments, comprising rotation (gyro) and acceleration sensors• a motherboard to electrically connect the internal modules and other components• a rear connector panel, including multiple separate output databuses (eight forADR data and four for IR data).• To achieve a high degree of fault tolerance, the ADIRU included BITE thatprovided monitoring and for isolation of faults within the unit. The BITE wasdesigned so that a wide range of ADIRU functions were monitored and a highproportion of faults would be detected by the ADIRU itself. In addition to faultdetection, the ADIRU’s BITE recorded routine maintenance information. BITErecords were stored in memory chips within the various modules. Furtherinformation on the operation of BITE functions of potential relevance to thedata-spike failure mode is provided in section 3.7.3.2.2 CPU moduleThe CPU 123 module performed the following functions:• monitored and controlled the other modules• conducted BITE tests, and managed and recorded BITE data• received data from the unit’s other modules, including flight data from the airdata input/output module and the inertial reference input/output module• processed the data (such as performing corrective calculations)• packaged the data in a format suitable for outputting to other aircraft systems(section 3.3.2)• sent the resulting data to the two input/output modules, which sent the data tothe other systems.ADR data was not passed through the inertial reference input/output module, and IRdata was not passed through the air data input/output module. Consequently, theCPU module was the only area within the ADIRU with the potential to directlyaffect ADR data, IR data and BITE memory. 124123124A CPU is the part of a digital computer system that executes instructions from a computerprogram or programs. It normally refers to a single integrated circuit.Other areas common to the ADR and IR parts were the power supply module, monitor module,rear connector panel and the motherboard. Although the power supply module, monitor module,- 111 -
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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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- xviii -
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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
Page 80 and 81: did not identify any faults. The BI
Page 82 and 83: Comparison of the three occurrences
Page 84 and 85: 1.17.2 Processes for reporting and
Page 87 and 88: 2 FACTUAL INFORMATION: ELECTRICAL F
Page 89 and 90: monitored external systems that pro
Page 91 and 92: Each FCPC used a number of paramete
Page 93 and 94: AOA computation logicThe FCPC softw
Page 95 and 96: Figure 29: FCPC processing of sever
Page 97 and 98: Table 19: Characteristics of elevat
Page 99 and 100: Simulation of AOA values for the fi
Page 101 and 102: 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: 3 FACTUAL INFORMATION: AIR DATA INE
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 and 154: manufacturer reported such BITE dat
Page 155 and 156: 3.6 Potential trigger types3.6.1 Ba
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
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4 FACTUAL INFORMATION: CABIN SAFETY
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Summary details of the cabin crew
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section, and the ninth flight atten
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Table 29: Significant cabin communi
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Figure 48: Example of damage to the
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4.3.2 Seat belt examinationsSix pas
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The flight crew’s procedures requ
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takeoff, landing or when the seat-b
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Table 31: Levels of injuryInjury le
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4.6.4 Injuries to seated occupants
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The percentage of occupants who wer
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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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