Stall warning and Alternate law
This post is part of the Airbus aircraft family and system safety thread.
According to an investigator from Indonesia’s National Transportation Safety Committee (NTSC) several alarms, including the stall warning, could be heard going off on the Cockpit Voice Recorder’s tape.
Now why is that so significant?
Recent work in complexity and robustness theory for engineered systems has highlighted that the architecture with which these systems are designed inherently leads to ‘robust yet fragile’ behavior. This vulnerability has strong implications for the human operator when he or she is expected to intervene in response to the failure of system.
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The QF 72 accident illustrates the significant effects that ‘small field’ decisions can have on overall system safety Continue Reading…
The fallout from the QF 72 in flight accident has now reached the courts with Australian Aviation reporting that passengers and crew have taken up a joint class action against Airbus and Northrop Grumman (the manufacturer of the faulty Air Data Inertial Reference Unit).
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Over the last couple of months I’ve posted on various incidents involving the Airbus A330 aircraft from the perspective of system safety. As these posts are scattered through my blog I thought I’d pull them together, the earliest post is at the bottom.
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I’ve just finished reading the ATSB’s second interim report on the the QF 72 in flight upset that resulted in two uncommaned pitch over events (1). In this accident one of the Air Data Inertial Reference Units (ADIRU) provided erroneous data in the form of transient spikes vales of the angle of attack AoA parameter to the flight control computers which then initiated two un-commanded extreme pitch overs.
This post is part of the Airbus aircraft family and system safety thread. Continue Reading…
So far as we know flight AF 447 fell out of the sky with its systems performing as their designers had specified, if not how they expected, right up-to the point that it impacted the surface of the ocean.
So how is it possible that incorrect air data could simultaneously cause upsets in aircraft functions as disparate as engine thrust management, flight law protection and traffic avoidance?
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The use of median value voting algorithms as part of fault tolerant design has become an almost ubiquitous design solution, especially for avionics systems. But have we really considered their suitability?
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The TCAS II specification credibility window can provide us with an insight into the magnitude initial unreliable air data parameters in the AF 447 disaster.
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The theory of Highly Optimised Tolerance (HOT) predicts that as technological systems evolve to become more robust to common perturbations they still remain vulnerable to rare events (Carlson, Doyle 2002) and this theory may give us an insight into the performance of modern integrated air data systems in the face of in-flight icing incidents.
With a Bachelor’s in Mechanical Engineering and a Master’s in Systems Engineering, Matthew Squair is a principal consultant with Jacobs Australia. His professional practice is the assurance of safety, software and cyber-security, and he writes, teaches and consults on these subjects. He can be contacted at mattsquair@gmail.com
