Archives For A330

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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The statement by, AirBus regarding the robustness of the AirBus AOA voting logic disclosed in the ATSB QF72 accident report raises some interesting questions as to what was actually meant by the term robustness.

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The QF 72 in flight pitch upset demonstrates the vulnerability of a redundant and presumed fault tolerant systems to situations where the real world does not accord with the assumptions made by designers.

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