Air data inertial reference unit: Difference between revisions

Revision as of 16:15, 25 April 2020

Revision as of 20:02, 10 May 2020

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|___location=Farnborough

|accessdate=2008-07-16

|archiveurl = https://web.archive.org/web/20061017052942/http://www.ainonline.com/Publications/farn/farn_02/farn_02d2_honeywellpg48.html |archivedate = 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|accessdate=2008-10-16|isbn=0-7803-3050-1}}</ref>

|publisher=[[Aviation International News]] via [[archive.org]]

|archiveurl = https://web.archive.org/web/20061017052942/http://www.ainonline.com/Publications/farn/farn_02/farn_02d2_honeywellpg48.html |archivedate = 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|accessdate=2008-10-16|isbn=0-7803-3050-1}}</ref>

==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.is/20070115043457/http://www.smartcockpit.com/pdf/plane/airbus/A330/systems/0019/ |url-status=dead |archive-date=15 January 2007 |title=Airline training guides, Aviation, Operations, Safety -Navigation A330 |work= |access-date=12 June 2009 }}</ref>

===Air data reference===

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===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&pgis=1|title=International Aerospace Abstracts|publisher=Cambridge Scientific Abstracts, Inc, [[American Institute of Aeronautics and Astronautics]]|year=1985|accessdate=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==

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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

|format = PDF

|title = AAIB Bulletin: 6/2006

|year = 2006

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{{cite web

| title = In-flight upset event, 240 km north-west of Perth, WA, Boeing Company 777-200, 9M-MRG, 1 August 2005

| work =

| publisher = [[Australian Transport Safety Bureau]]

| date = 2007-03-13

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

| format = PDF

| accessdate = 2008-10-15

}}</ref>

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{{cite web

| title = Emergency Airworthiness Directive (AD) 2005-18-51

| work =

| publisher = [[Federal Aviation Administration]]

| date = 2005-08-29

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| date = 2009-03-06

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

| format = PDF

| accessdate = 2009-03-07

}}</ref>