A secret partition (internal computer wall) on the US-made air data inertial reference unit (ADIRU) that Qantas blames for the in flight crisis that forced QF 72 to make an emergency landing at Learmonth on 7 October is about to be unlocked.

Its existence, only hinted at in the preliminary ATSB report into the accident, is causing consternation among airlines for whom there is now a question mark over the serviceability of equipment critical to the control of modern airliners. They simply don’t know the full information held by the ADIRU.

Crikey has been shown part of a private Qantas presentation on the accident, which injured 60 of its passengers and 14 of its crew aboard the Airbus A330-300 involved.

It draws attention to frequent unusual movements in the tail of the jet and disclosed that all three ADIRU units had be sent back to the maker, Northrop-Grumman because of third level data that was partitioned from examination by operators or accident investigators and could only be read in the Northrop-Grumman workshops.

This deeper level of data is apparently prohibited to users to protect proprietary aspects of the design from being copied or interfered with.

However the issue that has now emerged for the carriers including Qantas is that this secrecy might prevent them becoming aware of any deeper layer faults that should be fixed before an airliner is allowed to continue in service.

The Australian, French and US incident investigation authorities, and Airbus and Qantas will all be present this week when Northrop-Grumman starts unlocking all of the data contained in the three units on the A330, the two that appeared to work properly, and the one that ran amok.