Airbus A320/A330/A340 Electrical Flight Controls
Join Date: Nov 2006
Location: SoCalif
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The ADIRU should have set FAIL WARN in its output data bus words upon sending out faulty data. This is a highly monitored unit whose output should be proven to a probability of on the order of 10 to -9 of no undetected failures.
Either the ADIRU (design) engineers need to fix that, or the Bus (design) engineers need to fix their lack of monitoring of Sign Status Matrix. That ADIRU should have been automatically taken off-line as soon as it reported Fail Warn.
Back in the pioneering days of Area Navigation, I remember an Inertial Sensor Unit in the KSSU DC-10 that had a stuck minor bit in its output word. The unit would flag Fail Warn in its output data bus when the bit caused checksum fail, and the Nav Computer would drop it from calculations. However, the Nav Computer would accept every good word. This caused the Nav System to miss the approach gateway by more than 60 miles after a long overwater flight. The fix was to merely change the logic in the Nav Computer to require six good words after receiving one word flagged bad before accepting the Inertial Sensor's data again.
GB
Either the ADIRU (design) engineers need to fix that, or the Bus (design) engineers need to fix their lack of monitoring of Sign Status Matrix. That ADIRU should have been automatically taken off-line as soon as it reported Fail Warn.
Back in the pioneering days of Area Navigation, I remember an Inertial Sensor Unit in the KSSU DC-10 that had a stuck minor bit in its output word. The unit would flag Fail Warn in its output data bus when the bit caused checksum fail, and the Nav Computer would drop it from calculations. However, the Nav Computer would accept every good word. This caused the Nav System to miss the approach gateway by more than 60 miles after a long overwater flight. The fix was to merely change the logic in the Nav Computer to require six good words after receiving one word flagged bad before accepting the Inertial Sensor's data again.
GB
