Archives For in-flight upset

Flaws in the glass

19/07/2009

DO-178B and the B-777 9M-MRG Incident

In August 2005 a Boeing 777 experienced an in-flight upset caused by the aircraft’s Air Data Inertial Reference Unit (ADIRU), generating erroneous acceleration data. The software fault that caused this upset raises questions in turn about the DO-178 software development process. A subsequent investigation of the accident by the Australian Transportation Board (ATSB) identified that the following had occured:

  • accelerometer #5 failed on the first of June in a false high value output mode,
  • the ADIRU excluded accelerometer #5 from use in its computations,
  • the ADIRU unit remained in service with this failed component (1),
  • power to the ADIRU was cycled (causing a system reset),
  • accelerometer #6 then failed in-flight,
  • accelerometer #6 was excluded from use by the ADIRU,
  • the ADIRU then re-admitted accelerometer #5 into its computations, and
  • erroneous acceleration values were output to the flight computer.

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