Making it HOT for the Operator

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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Averages, Voting and System Robustness

The QF 72 accident illustrates the significant effects that ‘small field’ decisions can have on overall system safety.

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The QF72 A330 Accident – Send Lawyers, Guns & Money*

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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The Airbus Aircraft Family & System Safety

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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Integrated Vulnerability and QF72

Software temptations are virtually irresistible. The apparent ease of creating arbitrary behavior makes us arrogant. We become sorceror’s apprentices, foolishly believing we can control any amount of complexity. … We would be better off if we learned how and when to say no G.F. McCormick, When Reach Exceeds Grasp I’ve just finished reading the ATSB’s second [...]

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A Spectre is Haunting Airbus

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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HOT Voting Algorithms*

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 Credibility Window and AF 447

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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Highly Optimised Air Data

Modern air data systems have evolved from a federated set of air speed and altitude analog gauges to an integrated set of aerodynamic and thermodynamic electronic sensors, computers and displays. However in the case of air data systems the presence of a mach compensation feedback loop in the processing path inherently increases coupling and allows the propagation of dynamic pressure errors into temperature and static pressure calculations.

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