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‘Cosmic rays’ may have caused Qantas jet’s plunge

ANDREW HEASLEY AND ARI SHARP
November 18, 2009

Cosmic rays are being considered by air safety investigators as a possible cause of a Qantas plane plunging twice in quick succession on its way from Singapore to Perth in October last year.

Air safety investigators this morning brought down their second interim report into the flight QF72 incident, which left one flight attendant and 11 passengers with serious injuries, finding that an equipment glitch with one of three data collectors was a likely cause.

But the reason for the problems with the air data inertial reference unit, which gathers data from outside the plane and feeds it into the cockpit, remains unclear.

One explanation being considered for the October 7 incident is that cosmic or solar rays interfered with the system, noting that a single particle can cause problems with integrated circuits such as the one used in the data equipment.

“There is a constrant stream of high-energy galactic and solar radiation interacting with the Earth’s upper atmosphere,” the report noted. “This interaction creates a cascade of secondary particles. Some of the secondary particles, in particular neutrons, can affect aircraft avionics systems.”

The Airbus A330-303 was flying at 37,000 feet with 303 people on board when it plunged 650 feet before recovering to its original height and then plunging 400 feet.

The pilot declared a “mayday” an sought an emergency landing at Learmonth, Western Australia.

The data device experienced significant spikes in nine different categories of information, leading to the dramatic movements in the aircraft, which was using its autopilot system.

In releasing the report this morning, Australian Transport Safety Bureau safety investigator Ian Sangston said while the spikes could not yet be explained, changes to equipment had been taken to filter out extreme data.

“We don’t know the methodology of those spikes, however we understand the result of those spikes and how the upset occurred and there’s good safety action in place to ensure any spikes in future will not have that effect,” he told reporters in Canberra.

Airbus is changing the software that runs avionics on its A330 and A340 passenger jets following the incident and two others in recent years involving the data units.

Qantas has progressively installed the software patches on its Airbus fleet, and more software updates are due through next year, which once certified, will be installed on Airbuses worldwide.

Safety investigators have also found problems with aircraft seatbelts that can become unclasped unintentionally during a plummet, increasing injury risk.
Six passengers reported that despite having their seatbelts done up, three said tightly, that the buckle unfastened when the plane dived.

Investigators found buckles can flip open when they contact the seats’ armrests, a scenario that’s more likely if the seatbelt is being worn loosely

“We identified that if seatbelts aren’t secured low down on the hip as recommended by the operators, there is an instance where if the latch of the seatbelt is loose and can catch on the seat it can actually undo it, so we’re working with other authorities and manufacturers and so on to understand that,” Mr Sangston said.

A final report is expected by the middle of next year.

“We’ve implemented all actions required by regulators and and aircraft manufacturers to date,” the spokesman said.

“Following the incident we quickly introduced a number of new measures including enhanced flight crew procedures developed by Airbus to manually isolate potential…(avionics)…issues.

“We’ve also installed improved flight control software across the A330 fleet and these, in combination, have added additional layers of protection to prevent another similar incident.”

The investigators found the seatbelt sign was not illuminated while the plane was cruising and there was no policy or procedure requiring cabin crew to check or enforce seatbelt use, beyond take-offs and landings.

The Qantas spokesman defended the airline’s advice to passengers about seatbelts.

“We provide various information to passengers about the importance of wearing seatbelts. They’re designed to be worn firmly fitted and this is the instruction we give to passengers, along with the instruction that they should be worn at all times while the passenger is in their seat,” he said.

The seat belts fitted to Qantas Airbus jets were a standard seatbelt used by all operators, the spokesman said.

“Should the regulators introduce any requirements to change those seatbelts then we will certainly implement any changes that might be required.”

But changing seatbelts would be a massive undertaking for Qantas — and all airlines.

With about 220 planes in the Qantas fleet, carrying up to 300 people per plane, the airline would need to replace more than 60,000 buckles.