Air data inertial reference unit: Difference between revisions

Revision as of 14:34, 18 December 2020

Revision as of 17:21, 2 January 2021

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|url=http://findarticles.com/p/articles/mi_m0UBT/is_32_20/ai_n26957235

|title=The intricate complexity within an immaculate redundancy concern

|accessdateaccess-date=2008-07-16

|publisher=Air Safety Week

|date=August 14, 2006

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|title=Safety concern

|work=Air Safety Week

|accessdateaccess-date=2006-09-16

|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

|accessdateaccess-date=2008-07-16

|archiveurlarchive-url = https://web.archive.org/web/20061017052942/http://www.ainonline.com/Publications/farn/farn_02/farn_02d2_honeywellpg48.html |archivedatearchive-date = 2006-10-17}}</ref> and [[Boeing 777]].<ref>{{cite book|url=https://books.google.com/books?id=ZP9VAAAAMAAJ|title=Digital Avionics Systems|publisher=[[IEEE]], [[AIAA]]|year=1995|accessdateaccess-date=2008-10-16|isbn=0-7803-3050-1}}</ref>

==Description==

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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 |accessdateaccess-date=25 December 2016 }}</ref>

===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|accessdateaccess-date=2008-10-16}}</ref> The primary benefits of a ring laser over older mechanical [[gyroscope]]s are that there are no moving parts, it is rugged and lightweight, frictionless and does not resist a change in [[precession]].

==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 ADIRU's can lead to counter-intuitive behaviour for the crew in the event of a failure. In the case of [[Qantas Flight 72]], the captain switched the source of IR data from ADIRU1 to ADIRU3 following a failure of ADIRU1; however ADIRU1 continued to supply ADR data to the captain's primary flight display. In addition, the master flight control computer (PRIM1) was switched from PRIM1 to PRIM2, then PRIM2 back to PRIM1, thereby creating a situation of uncertainty for the crew who did not know which redundant systems they were relying upon.<ref name="harmful">

{{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 |accessdateaccess-date=8 June 2009}}</ref>

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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|publisher=US [[Federal Aviation Authority]]

|date=April 18, 2000

|accessdateaccess-date=2008-10-15

}}</ref><ref>

{{cite web

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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

|df =

}}</ref>

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|publisher=US [[Federal Aviation Authority]]

|date=August 6, 2008

|accessdateaccess-date=2008-10-15

}}</ref>

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|archive-date = 2008-10-22

|url-status = dead

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}}</ref>

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| date = 2007-03-13

| url = http://www.atsb.gov.au/publications/investigation_reports/2005/AAIR/pdf/aair200503722_001.pdf

| accessdateaccess-date = 2008-10-15

}}</ref>

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| date = 2005-08-29

| url = http://rgl.faa.gov/Regulatory_and_Guidance_Library%5CrgAD.nsf/0/25F9233FE09B613F8625706C005D0C53?OpenDocument#

| accessdateaccess-date = 2008-10-15

}}</ref>

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| date = 2009-03-06

| url = http://www.atsb.gov.au/publications/investigation_reports/2008/AAIR/pdf/AO2008070_interim.pdf

| accessdateaccess-date = 2009-03-07

}}</ref>

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|publisher=US [[Federal Aviation Authority]]

|date=6 August 2008

|accessdateaccess-date=2008-10-16

|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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|archive-date = 2008-10-17

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|date=28 June 2009

|publisher=aviationnewsrelease

}}</ref> On a 21 May 2009 [[Miami]]-[[Sao Paulo]] [[TAM Flight 8091]] registered as PT-MVB, and on a 23 June 2009 [[Hong Kong]]-[[Tokyo]] [[Northwest Airlines]] Flight 8 registered as N805NW each saw sudden loss of airspeed data at cruise altitude and consequent loss of ADIRS control.<ref>{{cite press release| url=https://www.ntsb.gov/news/2009/090625a.html |title=NTSB investigating two recent incidents involving possible A-330 speed and altitude indication anomalies |publisher= [[NTSB]] |date=25 June 2009 |accessdateaccess-date=14 October 2011}}</ref><ref>{{cite web |title=Brief of Incident |url=https://www.ntsb.gov/_layouts/ntsb.aviation/GeneratePDF.aspx?id=DCA09IA055&rpt=first |date=18 July 2011 |publisher=NTSB }}</ref><ref>{{cite web |title=Brief of Incident |url= https://www.ntsb.gov/_layouts/ntsb.aviation/GeneratePDF.aspx?id=DCA09IA064&rpt=fi |publisher=NTSB |date=27 June 2011 }}</ref>

===Ryanair Flight 6606===

On 9 October 2018, the [[Boeing 737 Next Generation|Boeing 737-800]] 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|last=|first=|date=|website=|url-status=live|archive-url=|archive-date=|access-date=}}</ref> with the following recommendation:<blockquote>It is recommended that Boeing Commercial Aircraft amend the Boeing 737 Quick Reference Handbook to include a non-normal checklist for situations when pitch and roll comparator annunciations appear on the attitude display.</blockquote>

==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=http://www.google.com/patents?id=Aw8PAAAAEBAJ&dq=6654685|title=US Patent 6654685 - Apparatus and method for navigation of an aircraft|date=2003-11-25|accessdateaccess-date=2008-10-16|publisher=[[United States Patent Office]]|author =Melville Duncan W. McIntyre, [[Boeing]]}}

{{Flight instruments}}