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Air data inertial reference unit (ADIRU) susceptibility to single event effects

Issue number: AO-2008-070-SI-08
Who it affects: All operators of aircraft fitted with LTN-101 ADIRUs
Issue owner: Northrop Grumman Corporation
Operation affected: Aviation: Air transport
Background: Investigation Report AO-2008-070
Date: 19 December 2011

Safety issue description

The LTN-101 air data inertial reference unit (ADIRU) model had a demonstrated susceptibility to single event effects (SEE). The consideration of SEE during the design process was consistent with industry practice at the time the unit was developed, and the overall fault rates of the ADIRU were within the relevant design objectives.

Proactive Action

Action organisation: Northrop Grumman Corporation
Action number: AO-2008-070-NSA-126
Date: 19 December 2011
Action status: Closed
The ADIRU manufacturer conducted a ‘theoretical analysis’ of the potential for a single event upset (SEU) on the LTN-101 ADIRU. The overall result of this analysis was that, after considering the influence of SEEs, the ADIRU still met the aircraft manufacturer’s safety objectives.
Current issue status: Partially addressed
Status justification:

The theoretical analysis was an assessment of the potential for SEE to have an influence. It did not actually reduce the potential of SEE for existing units.

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Last update 11 February 2014