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Gr.Viper

Got bugs in your avionics?

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On 7 October 2008, the Australian-owned A330-303 aircraft was cruising at 37,000 feet when the autopilot disengaged and the aircraft rose, before plunging downwards sharply, injuring 110 of the aircraft’s 303 passengers and three-quarters of the cabin crew. Three minutes later the aircraft did it again

 

http://www.theregister.co.uk/2011/12/20/bug_cause_aussie_a330_plunge/

The investigation is complete and apparently

one of the three air data inertial reference units (ADIRUs) installed on the A330-303 aircraft began to malfunction and went into failure mode before the incident. It then began feeding false information into the flight control systems, and the software algorithms designed to handle the information couldn’t cope, causing the erratic behavior.

The link to full report is in the article.

 

And the classic punchline...

The problem was fixed by turning the unit off and then on again.

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With it being a Triplex system the "voter" circuity should have seen two very similar sets of data and one Wildly off set and voted to disregard the dodgy set so for it not to have done that is a huge worry for the makers (and the pilots at the time!) as it essentially makes it a single mean point of failure.

 

A good 75-80% of our aircrew's "snags" are down to a computer of some sort going wibble (either from heat, program corruption etc) which is solved by removing power and switching it back on again after a minute or two. Unfortunately while flying our A/C is designed with a "keep alive in OFF" mode where switching the unit OFF just puts it into standby rather than removing voltage (incase the aircrew accidentally switch something off they can switch it back on quickly without a warm up phase). This means we can't get the aircrew to just switch it off in flight as it needs power either removing from the jet (Generators off) or the CB pulling, neither of which could be done in the air.

 

Another great feature from the guys & gals at BAE.

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bugs in my avionics? i got ants all over the compass, the HUD, the gauges, the clock, the monitors, the canopy, the crack pipe...wait, nevermind

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Restart engineers at work, I'm one of those guilty at times.

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