[SystemSafety] Looking for information about safety-critical software faults in road vehicles

Peter Bernard Ladkin ladkin at causalis.com
Wed Aug 22 13:48:09 CEST 2018

On 2018-08-22 10:50 , Peter Bishop wrote:
> A better source might be airworthiness directives (AD). These are fixes
> to aircraft systems mandated by organisations like the FAA in response
> to reported incidents (i.e. present a risk to flight safety).

I agree. They are also just in two places (FAA and EASA) and the EASA WWW site is easily searchable.

> While
> software is not mentioned, directives to update flight control systems
> are most probably (almost certainly?) software related.
Here is a catch. There is lots of stuff that is design-related which is most easily fixed in SW.
That doesn't mean the source was a SW issue.

Take Learmonth, the Qantas A330 incident in which the PFCS went on a roller-coaster ride. Trigger
was a series of signal spikes coming from an ADIRU. Lots of signal anomalies are filtered in the
PFCS SW, but this one wasn't. I understand that it had been considered during design and a decision
was made that such a signal would not be generated in an otherwise-healthy ADIRU. So they didn't
filter. The fix is obviously SW: put in a filter. But the original problem was a misjudgement. (BTW,
they never did find anything with the ADIRU to explain the signal.)

I wouldn't be surprised to find that a majority of SW fixes are for such things which do not have a
SW origin.


Prof. Peter Bernard Ladkin, Bielefeld, Germany
Je suis Charlie
Tel+msg +49 (0)521 880 7319  www.rvs-bi.de

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