Archives For A330

QF 72 (Image Source: Terence Ong)

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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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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Reading the 2nd BEA interim report’s analysis of ACARS message timing provides us with a further refinement of a calculation of AF 447′s terminal vertical speed (posted here) based on the cabin vertical speed advisory.

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Invalid air data may have triggered the cabin pressure differential safety function on AF 447.

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Recent incidents involving Airbus aircraft have again focused attention on their approach to cockpit automation and it’s interaction with the crew.

Underlying the current debate is perhaps a general view that the automation should somehow be ‘perfect’, and that failure of automation is also a form of moral failing (1). While this weltanschauung undoubtedly serves certain social and psychological needs the debate it engenders doesn’t really further productive discussion on what could or indeed should be done to improve cockpit automation.

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A cross walk of the interim investigation accident reports issued by the ATSB and BEA for the QF72 and AF447 accidents respectively shows that in both accidents the inertial reference units that are part of the onboard air data inertial reference unit (ADIRU) that exhibited anomalous behaviour also declared a failure. Why did this occur?

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Authors Note. Below is my original post on the potential causes of the AF 447 cabin altitude advisory, I concluded that there were a number of potential causes one of which could be an erroneous altitude input from the ADIRU. What I didn’t consider was that the altitude advisory could have been triggered by correct operation of the cabin pressure control system, see  The AF 447 cabin vertical speed advisory and Pt II for more on this.

The last ACARS transmision received from AF 447 was the ECAM advisory that the cabin altitude (pressure) variation had exceeded 1,800 ft/min for greater than 5 seconds. While some commentators have taken this message to indicate that the aircraft had suffered a catastrophic structural failure, all we really know is that at that point there was a rapid change in reported cabin altitude. Given the strong indications of unreliable air data from other on-board systems, perhaps it’s worthwhile having a look for other potential causes of such rapid cabin pressure changes.

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TCAS Indicator (Image Source: Public Domain)

What TCAS can tell us about AF447 (Updated 27 Sept 09)

The BEA interim report on the AF447 accident confirms that the Traffic Alert and Collision Avoidance System (TCAS) had become inoperative during the early part of the event sequence for an, as yet, un-identified reason. The explanation may actually be fairly straight forward and lie within the fault tolerance requirements of the TCAS specification. Continue Reading…

Reading the ATSB interim report on the QF72 in flight accident one could easily overlook the statement, “…the crew reported that the (ECAM (1)) messages were constantly scrolling, and they could not effectively interact with the ECAM to action and/or clear the messages.”. So why did the A330 ECAM display fail during such a critical event?

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