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{{Short description|Flight instrument}}
An '''
{{Cite web
|url=http://findarticles.com/p/articles/mi_m0UBT/is_32_20/ai_n26957235
|title=The intricate complexity within an immaculate redundancy concern
|
|publisher=Air Safety Week
|date=August 14, 2006
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|title=Safety concern
|work=Air Safety Week
|
|date=May 5, 2005
}}</ref> It may be complemented by a secondary attitude air data reference unit (SAARU), as in the [[Boeing 777]] design.<ref name="gremlins">
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|date=22–28 July 2002
|___location=Farnborough
|
|
==Description==
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</ref> The No 3 ADIRU is a [[Redundancy (engineering)|redundant]] unit that may be selected to supply data to either the commander's or the co-pilot's displays in the event of a partial or complete failure of either the No 1 or No 2 ADIRU. There is no cross-channel redundancy between the Nos 1 and 2 ADIRUs, as No 3 ADIRU is the only alternate source of air and inertial reference data. An inertial reference (IR) fault in ADIRU No 1 or 2 will cause a loss of [[Angle of attack|attitude]] and navigation information on their associated [[EFIS#Primary flight display (PFD)|primary flight display]] (PFD) and navigation display (ND) screens. An air data reference (ADR) fault will cause the loss of airspeed and altitude information on the affected display. In either case the information can only be restored by selecting the No 3 ADIRU.<ref name="art5" />
Each ADIRU comprises an ADR and an inertial reference (IR) component.<ref name="urlA330 - Navigation">{{cite web|publisher=smartcockpit.com |url=http://www.smartcockpit.com/pdf/plane/airbus/A330/systems/0019/ |archive-url=https://archive.
===Air data reference===
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|access-date=2008-07-14
|publisher=Boeing Aero Magazine, Issue 08
| archive-url= https://web.archive.org/web/20080612001822/http://www.boeing.com/commercial/aeromagazine/aero_08/erroneous_textonly.html| archive-date= 12 June 2008 <!--DASHBot-->| url-status= live}}</ref> Ram air pressure and static pressures used in calculating [[airspeed]] are measured by small ADMs located as close as possible to the respective [[Pitot tube|pitot]] and static pressure sensors. ADMs transmit their pressures to the ADIRUs through [[ARINC 429]] data buses.<ref>{{cite web |url=http://www51.honeywell.com/aero/common/documents/Air_Data_Module.pdf |publisher=Honeywell |title=Air Data Module |
===Inertial reference===
The [[Inertial reference unit|IR]] component of an ADIRU gives attitude, flight path vector, ground speed and positional data.<ref name="art5" /> The [[ring laser gyroscope]] is a core enabling technology in the system, and is used together with [[accelerometer]]s, [[GPS]] and other sensors to provide raw data.<ref>{{cite book|url=https://books.google.com/books?id=5ShYAAAAMAAJ|title=International Aerospace Abstracts|publisher=Cambridge Scientific Abstracts, Inc, [[American Institute of Aeronautics and Astronautics]]|year=1985|
==Complexity in redundancy==
Analysis of complex systems is itself so difficult as to be subject to errors in the certification process. Complex interactions between flight computers and
{{cite web |url=http://www.dcs.gla.ac.uk/~johnson/papers/ISSC09/ADIRU_Accident_Submission.pdf |title=The Dangers of Interaction with Modular and Self-Healing Avionics Applications: Redundancy Considered Harmful |author1=C.W. Johnson |author2=C. Michael Holloway |date=2 February 2009 |
Reliance on redundancy of aircraft systems can also lead to delays in executing needed repairs, as airline operators rely on the redundancy to keep the aircraft system working without having to repair faults immediately.<ref name="art5"/><ref name="art2"/><ref name="gremlins"/><ref name="harmful"/>
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===FAA Airworthiness directive 2000-07-27===
On May 3, 2000, the FAA issued [[airworthiness directive]] 2000-07-27, addressing dual critical failures during flight, attributed to power supply issues affecting early [[Honeywell]] HG2030 and HG2050 ADIRU [[ring laser gyro]]s used on several Boeing 737, 757, Airbus A319, A320, A321, A330, and A340 models.<ref name="art2" /><ref>{{cite web
|url=http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/WebSearchDefault?SearchView&Query=AD%202000-07-27&SearchOrder=1&SearchMax=0&SearchWV=TRUE&SearchFuzzy=FALSE&Start=1&Count=100
▲ |url=http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/WebSearchDefault?SearchView&Query=AD%202000-07-27&SearchOrder=1&SearchMax=0&SearchWV=TRUE&SearchFuzzy=FALSE&Start=1&Count=100#
|title=Various transport category airplanes equipped with certain Honeywell Air Data Inertial Reference Units
|publisher=US [[Federal Aviation
|date=April 18, 2000
|
|archive-date=2009-06-06
}}</ref><ref>▼
|archive-url=https://web.archive.org/web/20090606142545/http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/WebSearchDefault?SearchView&Query=AD%
|url-status=dead
▲ }}</ref><ref>
{{cite web
|url = http://www.casa.gov.au/airworth/airwd/ADfiles/equip/inst/INST-045.pdf
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|archive-url = https://web.archive.org/web/20080805050006/http://casa.gov.au/airworth/airwd/ADfiles/equip/inst/INST-045.pdf
|archive-date = August 5, 2008
}}</ref>
===Airworthiness directive 2003-26-03===
On 27 January 2004 the FAA issued airworthiness directive 2003-26-03 (later superseded by AD 2008-17-12) which called for modification to the mounting of ADIRU3 in Airbus A320 family aircraft to prevent failure and loss of critical attitude and airspeed data.<ref name="art2" /><ref>{{cite web
|url=http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/WebSearchDefault?SearchView&Query=AD%202003-26-03&SearchOrder=1&SearchMax=0&SearchWV=TRUE&SearchFuzzy=FALSE&Start=1&Count=100
▲ |url=http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/WebSearchDefault?SearchView&Query=AD%202003-26-03&SearchOrder=1&SearchMax=0&SearchWV=TRUE&SearchFuzzy=FALSE&Start=1&Count=100#
|title=Airbus model A318, A319, A320, and A321 series airplanes equipped with certain Northrop Grumman (formerly Litton) Air Data Inertial Reference Units
|publisher=US [[Federal Aviation
|date=August 6, 2008
|
|archive-date=2009-06-06
}}</ref>▼
|archive-url=https://web.archive.org/web/20090606142550/http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/WebSearchDefault?SearchView&Query=AD%202003-26-03&SearchOrder=1&SearchMax=0&SearchWV=TRUE&SearchFuzzy=FALSE&Start=1&Count=100
|url-status=dead
▲ }}</ref>
===Alitalia A320===
[[File:"Alitalia" I-BIKE (3097537511).jpg|thumb|250x250px|I-BIKE, the aircraft involved in the A320 incident]]
On 25 June 2005, an [[Alitalia]]<!-- see http://www.baaa-acro.com/Photos-27/I-BIKE.jpg --> [[Airbus A320-200]] registered as I-BIKE departed [[Milan]] with a defective ADIRU as permitted by the [[Minimum Equipment List]]. While approaching [[London Heathrow Airport]] during deteriorating weather another ADIRU failed, leaving only one operable. In the subsequent confusion the third was inadvertently reset, losing its reference heading and disabling several automatic functions. The crew was able to effect a safe landing after declaring a [[Pan-pan]].<ref>{{cite web
|url = http://www.aaib.dft.gov.uk/cms_resources/Airbus%20A320-200,%20I-BIKE%2006-06.pdf
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|archive-date = 2008-10-22
|url-status = dead
}}</ref>
===Malaysia Airlines Flight 124===
[[File:Malaysia Airlines B777-200ER(9M-MRG) (4296895579).jpg |thumb|250x250px|9M-MRG, the aircraft involved as flight 124]]
On 1 August 2005, a serious incident involving [[Malaysia Airlines]] Flight 124 occurred when an ADIRU fault in a [[Boeing 777|Boeing 777-2H6ER]] (9M-MRG) flying from [[Perth Airport|Perth]] to [[Kuala Lumpur International Airport|Kuala Lumpur International]] caused the aircraft to act on false indications, resulting in uncommanded manoeuvres.<ref>{{ASN accident | id = 20050801-1 | title = Malaysia Airlines Flight 124 | accessdate = 2008-10-15}}</ref> In that incident the incorrect data impacted all [[flight dynamics|planes of movement]] while the aircraft was climbing through {{convert|38000|ft|m|-2}}. The aircraft pitched up and climbed to around {{convert|41000|ft|m|-2}}, with the stall warning activated. The pilots recovered the aircraft with the autopilot disengaged and requested a return to Perth. During the return to Perth, both the left and right autopilots were briefly activated by the crew, but in both instances the aircraft pitched down and banked to the right. The aircraft was flown manually for the remainder of the flight and landed safely in Perth. There were no injuries and no damage to the aircraft. The ATSB found that the main probable cause of this incident was a latent software error which allowed the ADIRU to use data from a failed [[accelerometer]].<ref>{{cite web
| title = In-flight upset event, 240 km north-west of Perth, WA, Boeing Company 777-200, 9M-MRG, 1 August 2005
| publisher = [[Australian Transport Safety Bureau]]
| date = 2007-03-13
| url = http://www.atsb.gov.au/publications/investigation_reports/2005/AAIR/pdf/aair200503722_001.pdf
|
| archive-date = 2021-03-15
}}</ref>▼
| archive-url = https://web.archive.org/web/20210315122511/http://www.atsb.gov.au/publications/investigation_reports/2005/AAIR/pdf/aair200503722_001.pdf
| url-status = dead
▲ }}</ref>
The US [[Federal Aviation Administration]] issued Emergency Airworthiness Directive (AD) 2005-18-51 requiring all 777 operators to install upgraded software to resolve the error.<ref>
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| date = 2005-08-29
| url = http://rgl.faa.gov/Regulatory_and_Guidance_Library%5CrgAD.nsf/0/25F9233FE09B613F8625706C005D0C53?OpenDocument#
|
}}</ref>
===Qantas Flight 68===
[[File:Airbus A330-303 ‘VH-QPA’ QANTAS.jpg |thumb|250x250px|VH-QPA, the aircraft involved as both flight 68 and [[Qantas Flight 72|72]]]]
On 12 September 2006, [[Qantas]] Flight 68, [[Airbus A330]] registration VH-QPA, from [[Singapore]] to [[Perth, Western Australia|Perth]] exhibited ADIRU problems but without causing any disruption to the flight. At {{convert|41000|ft|m}} and estimated position {{convert|530|NM|km}} north of [[Learmonth, Western Australia]],<ref name="ATSB_InterimReport" /> ''NAV IR1 FAULT'' then, 30 minutes later, ''NAV ADR 1 FAULT'' notifications were received on the [[Electronic Centralised Aircraft Monitor|ECAM]] identifying navigation system faults in [[Inertial Reference Unit]] 1, then in ADR 1 respectively. The crew reported to the later [[Qantas Flight 72]] investigation involving the same airframe and ADIRU that they had received numerous warning and caution messages which changed too quickly to be dealt with. While investigating the problem, the crew noticed a weak and intermittent ''ADR 1 FAULT'' light and elected to switch off ADR 1, after which they experienced no further problems. There was no impact on the flight controls throughout the event. The ADIRU manufacturer's recommended maintenance procedures were carried out after the flight and system testing found no further fault.<ref name="ATSB_InterimReport" />
===Jetstar Flight 7===
[[File:VH-EBC Airbus A330 Jetstar in White C-s (7173193593).jpg|thumb|250x250px|VH-EBC, the aircraft involved as flight 7]]
On 7 February 2008, a similar aircraft (VH-EBC) operated by Qantas subsidiary [[Jetstar Airways]] was involved in a similar occurrence while conducting the JQ7 service from Sydney to Ho Chi Minh City, Vietnam. In this event - which occurred {{convert|1760|NM|km}} east of Learmonth - many of the same errors occurred in the ADIRU unit. The crew followed the relevant procedure applicable at the time and the flight continued without problems.<ref name="ATSB_InterimReport">{{cite web
| title = In-flight upset, 154 km west of Learmonth, WA, 7 October 2008, VH-QPA, Airbus A330-303 - Interim Factual
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| date = 2009-03-06
| url = http://www.atsb.gov.au/publications/investigation_reports/2008/AAIR/pdf/AO2008070_interim.pdf
|
| archive-date = 2018-11-23
}}</ref>▼
| archive-url = https://web.archive.org/web/20181123163038/http://www.atsb.gov.au/publications/investigation_reports/2008/AAIR/pdf/AO2008070_interim.pdf
| url-status = dead
▲ }}</ref>
The ATSB has yet to confirm if this event is related to the other Airbus A330 ADIRU occurrences.<ref name="ATSB_InterimReport" />▼
===Airworthiness directive 2008-17-12===
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|url=http://content.atp.com/ADs/pdf/081712.pdf?JServSessionIdroot=d7d0g7xvd1.JS1
|title=AD 2008-17-12 Airbus
|publisher=US [[Federal Aviation
|date=6 August 2008
|
|archive-url=https://web.archive.org/web/20090617060150/http://content.atp.com/ADs/pdf/081712.pdf?JServSessionIdroot=d7d0g7xvd1.JS1
|archive-date=17 June 2009
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}}</ref>
===[[Qantas Flight 72]]===▼
▲The ATSB has yet to confirm if this event is related to the other Airbus A330 ADIRU occurrences.<ref name="ATSB_InterimReport" />
▲===Qantas Flight 72===
On 7 October 2008, [[Qantas Flight 72]], using the same aircraft involved in the Flight 68 incident, departed Singapore for Perth. Some time into the flight, while cruising at 37,000 ft, a failure in the No.1 ADIRU led to the autopilot automatically disengaging followed by two sudden uncommanded [[flight dynamics|pitch]] down manoeuvres, according to the Australian Transport Safety Bureau (ATSB). The accident injured up to 74 passengers and crew, ranging from minor to serious injuries. The aircraft was able to make an emergency landing without further injuries. The aircraft was equipped with a [[Northrop Grumman]] made ADIRS, which investigators sent to the manufacturer for further testing.<ref>
{{Cite news
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|date=14 October 2008
|access-date=2008-10-15
| archive-url= https://web.archive.org/web/20081016061452/http://www.abc.net.au/news/stories/2008/10/14/2391134.htm| archive-date= 16 October 2008 <!--DASHBot-->| url-status=
|url = http://www.theaustralian.news.com.au/business/story/0,28124,24506830-36418,00.html
|title = US tests on false data sent on Qantas jet over WA
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|archive-date = 2008-10-17
|url-status = dead
}}</ref>
===Qantas Flight 71===
[[File:VH-QPG A330-303 Qantas SIN 02APR06 (5915938802).jpg|thumb|250x250px|VH-QPG, the aircraft involved as flight 71]]
On 27 December 2008, Qantas Flight 71 from Perth to Singapore, a different Qantas A330-300 with registration VH-QPG<ref>{{cite web |url=http://asasi.org/papers/2009/QF72%20Learmonth%20A330%20Pitch%20Events%20Presented%20by%20Mike%20Walker.pdf |title=Learmonth A330 pitch events |author
| title = Qantas Airbus A330 incident, 480km North West of Perth on 27 December 2008
| publisher = Australian Transport Safety Bureau
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On 15 January 2009, the [[European Aviation Safety Agency]] issued [http://ad.easa.europa.eu/ad/2009-0012-E Emergency Airworthiness Directive No 2009-0012-E] to address the above A330 and A340 Northrop-Grumman ADIRU problem of incorrectly responding to a defective inertial reference. In the event of a NAV IR fault the directed crew response is now to "select OFF the relevant IR, select OFF the relevant ADR, and then turn the IR rotary mode selector to the OFF position." The effect is to ensure that the faulted IR is powered off so that it no longer can send erroneous data to other systems.<ref name="ATSB_InterimReport" />
===[[Air France Flight 447]]===
On 1 June 2009, [[Air France]] [[Air France Flight 447|Flight 447]], an Airbus A330 en route from [[Rio de Janeiro]] to [[Paris]], crashed in the Atlantic Ocean after transmitting automated messages indicating faults with various equipment, including the ADIRU.<ref>
{{cite news
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|date=28 June 2009
|publisher=aviationnewsrelease
}}</ref> On a 21 May 2009 [[Miami]]
===Ryanair Flight 6606===
[[File:Boeing 737-800 ‘EI-GJT’ Ryanair (53760657763).jpg|thumb|EI-GJT, the aircraft involved as flight 6606.]]
On 9 October 2018, the [[Boeing 737 Next Generation|Boeing 737-800]] with registration EI-GJT, operating the flight from Porto Airport to Edinburgh Airport suffered a left ADIRU failure that resulted in the aircraft pitching up and climbing 600 feet. The left ADIRU was put in ATT (attitude-only) mode in accordance with the [[Quick Reference Handbook]], but it continued to display erroneous attitude information to the captain. The remainder of the flight was flown manually with an uneventful landing. The UK's AAIB released the final report on 31 October 2019,<ref>{{Cite web|url=https://www.gov.uk/aaib-reports/aaib-investigation-to-boeing-737-8as-ei-gjt|title=AAIB investigation to Boeing 737-8AS, EI-GJT
==See also==
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|access-date=2008-10-16
| archive-url= https://web.archive.org/web/20080906001423/http://www.boeing.com/commercial/aeromagazine/aero_08/erroneous_textonly.html| archive-date= 6 September 2008 <!--DASHBot-->| url-status= live}}
* {{cite web|url=
{{Flight instruments}}
[[Category:Aircraft instruments]]▼
[[Category:Aerospace engineering]]
▲[[Category:Aircraft instruments]]
[[Category:Avionics]]
[[Category:Flight control systems]]
[[Category:Global Positioning System]]▼
[[Category:Navigational equipment]]
[[Category:Technology systems]]
▲[[Category:Global Positioning System]]
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