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Old 3rd Jun 2009, 12:52
  #684 (permalink)  
Join Date: Sep 2007
Location: Melbourne
Posts: 180
So, can an Air France pilot/engineer tell us which ADIRU manufacturer they use?
Thanks, RAD ALT ALIVE - so I got it wrong, Litton or Honeywell IS a customer option. So yes, it would be interesting (though not in any sense conclusive) to know which option Air France chose.

About the Qantas Learmonth incident, I discover that there were in fact three similar occurrences in quick succession (the first two being Qantas, the other unknown) and three cumulative Airworthiness Directives have issued, both covering most of the A330/340 range - significantly, those equipped with the Northrop Grumman (now Litton) ADIRUs.

Deciphering ADs is a bit like cracking the WW2 Enigma codes, so if I've got anything wrong someone please set me right.

In the first incident, the ADIRU started feeding erroneous data to the Airbus 'protection' system. So, although the aeroplane was flying level, the flight computers got the idea that it was climbing steeply - and therefore rammed the nose down.

"Investigations highlighted that at time of the event the Air Data Reference 1 (ADR) part of ADIRU1 was providing erroneous and temporary wrong parameters in a random manner. This abnormal behaviour of the ADR1 led to several consequences such as unjustified stall and over speed warnings, loss of attitude information on Captain Primary Flight Display (PFD) and several ECAM warnings. Among the abnormal parameters, the provided Angle of Attack (AoA) value was such that the flight control computers commanded a sudden nose down aircraft movement, which constitutes an unsafe condition. At this stage of the investigation, the analysis of available data indicates that ADIRU 1 abnormal behaviour is likely to be at the origin of the event. Due to similar design, Airbus A340 aircraft are also impacted by this issue."

The pilots eventually regained control, but only by turning off all the automatic stuff and reverting to 'alternate law' and doing an emergency landing at Learmonth. But 40-odd people were injured.

An AD was issued directing that that should be done any time there was a re-occurrence. But then another Qantas bird had the same problem, luckily without any injuries, approaching Perth. They followed the new procedure but it apparently didn't work! So a second AD was issued, and following yet another incident (don't know who or where that was) yet a third one went out:-

"Since that AD was issued, it has been reported that the “OFF” light did not illuminate in the cockpit after setting the IR and ADR pushbuttons to OFF. Investigation has determined that the ADIRU was indeed sometimes affected by another failure condition.

To prevent such a failure, the operational procedure has been updated to instruct the flight crew to de-energize the ADIRU if the “OFF” light is not illuminated after setting the IR and ADR pushbuttons to OFF.

Consequently, AD 2008-0225-E, which superseded AD 2008-0203-E, required accomplishment of the updated AFM operational procedure. Since this second AD was issued, a new in service event has been reported highlighting that, in some failure cases, even though the “OFF” light illuminates in the cockpit after setting the IR and ADR pushbuttons to OFF, the IR could keep providing erroneous data to other systems.

In order to address all identified failure cases, de-energizing the affected ADIRU must be done by setting the IR mode rotary selector to OFF. Consequently, this AD, which supersedes AD 2008-0225-E, requires accomplishment of the updated AFM operational procedure."

You can read the whole latest AD here (click on 'Download' at the bottom):-

EASA Airworthiness Directives Publishing Tool

Can't claim to understand it all by a long chalk - in the things I used to fly, a radio (or even an engine!) was an expensive luxury! But I get the feeling that the pilots are being told, "If the inertia gimmicks start talking nonsense to the auto controls, and go ON doing it, turn them ALL off and go back to 'seat of the pants' flying......."

Thing is, I'm struck by the similarity of the earlier cases with what appears to have happened to Air France (on the basis of the 'Aviation Herald,' anyway):-

"New information provided by sources within Air France suggests, that the ACARS messages of system failures started to arrive at 02:10Z indicating, that the autopilot had disengaged and the fly by wire system had changed to alternate law. Between 02:11Z and 02:13Z a flurry of messages regarding ADIRU and ISIS faults arrived, at 02:13Z PRIM 1 and SEC 1 faults were indicated, at 02:14Z the last message received was an advisory regarding cabin vertical speed. That sequence of messages could not be independently verified."

So it reverted to 'alternate law' (whether automatically or by pilot action, we don't know) and then ISIS packed in (which I take to mean that the emergency panel lighting packed in and the instruments went black).........

No way you could fly through a storm at 35,000 feet, presumably in cloud, with no autopilot and no instruments?
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