Australian investigators are to examine whether cosmic radiation played a role in the still-unexplained in-flight upset to a Qantas Airbus A330 in October last year.

The inquiry has already determined that an air data inertial reference unit (ADIRU) provided erroneous data spikes just before the upset.

Some of these spikes, in the angle-of-attack data, were not filtered by flight-control computers, which then commanded abrupt pitch-down movements.

The Australian Transport Safety Bureau (ATSB) has conducted extensive examination and testing of the suspect ADIRU, to check for electronic malfunctions, physical defects and possible problems in its software.

Qantas A330 animation

Investigators have also carried out tests flights, using the A330 involved, to check whether the ADIRU might have been subject to electromagnetic interference.

None of these tests have revealed any anomalies which might have explained the jet's behaviour.

Given the lack of evidence of a problem with the system, the ATSB is considering - among other avenues of inquiry - the possibility of a 'single event effect', generated by particle impact from cosmic radiation.

Upper-atmosphere collisions involving high-energy solar or intergalactic radiation can create secondary stray particles - notably neutron showers which have the potential to interact with, and damage, high-density integrated circuits.

"[Single event effects] have been suspected of generating some of the soft errors that occur in a wide range of different aircraft systems," says the ATSB. These 'soft' errors include non-destructive changes in logic states within digital electronics.

"The investigation team is evaluating the relevance, if any, of [single event effects] to the ADIRU fault that resulted in spikes being produced in ADIRU parameters," the ATSB adds.

Investigators are also assessing whether a known fault, known as 'dozing', might have contributed to the A330 upset.

The 'dozing' fault is a temporary issue which results in the ADIRU ceasing to output data for the remainder of the flight, although it resumes normal operation after power has been cycled on the ground.

Eleven passengers and a flight attendant were seriously injured during the upset, which occurred as flight QF72 was operating the Singapore-Perth route on 7 October last year.

Source: Air Transport Intelligence news