Source : THE AGE NEWS
By Chris Zappone
Jetstar has confirmed that its planes are flying normally again after a mystery glitch related to the global positioning system (GPS) forced delays and cancellations last week.
However, the aviation regulator has revealed the precise cause of the faults is still unknown, with the Civil Aviation Safety Authority saying it was “working with Jetstar to better understand the cause of the issue which affected aircraft position broadcasts.”
A mystery glitch halted some Jetstar flights last week. Credit: Kate Geraghty
“Navigation systems and safety were not affected.”
Two flights from Australia to Bali were cancelled last week, and others were delayed, after faults in the GPS on Jetstar Airbus A320 Neos and A321 Neos prevented the flights from taking off.
The airline said it understood “the fault message was caused by a satellite signal issue” that occurred from May 21 to May 23 AEST.
“Currently, this fault is not reoccurring. We continue to monitor closely,” a Jetstar spokesperson said.
GPS, a much-used navigation tool, determines a position by measuring proximity to an array of satellites in orbit. The equipment relies on several satellites to make a location reading.
Qantas-owned Jetstar said signals sent from the satellites were creating a fault message onboard the planes, which required the systems to be reset, delaying flights or forcing their cancellation.
Airbus, the planes’ manufacturer, told this masthead: “We understand that the fault messages on the aircraft were caused by a satellite signal issue.”
Aircraft navigation systems have numerous GPS units that receive data from different satellite constellations, Airbus said, noting that planes also have inertial reference systems and radio navigation aids.
These overlapping systems provide “redundancy in the event of an anomaly in-flight”.
“If a GPS anomaly is detected on the ground, it is standard operating procedure to check and reset the system before the next flight,” the Toulouse-based aircraft manufacturer said.
Whatever happened on the satellite side remains a mystery, though, with experts uncertain how a change to a satellite could cause faults with the GPS unit called ADS-B. It was also unclear if this glitch could affect Jetstar’s plane again.
An industry official with some knowledge of the situation said: “All is well that, for now, ends well.
“It looks like a satellite software update may have caused the problem. That was rolled back, and the aircraft systems have worked normally since.”
A spokesperson from Jetstar said the issue occurred when “a particular satellite has been above Australia from around 5pm to 5am (AEST).”
It’s understood that Jetstar acted in accordance with approved safety procedures, and regulators were satisfied that safety has been maintained throughout the issue which persisted from Wednesday to Friday.
The GPS fault also caused delays on Jetstar flights to Bali, Fiji and Hobart from Australia’s east coast on Thursday. No other Qantas-owned aircraft were affected by the faults.
A spokesperson for Virgin Australia said last week that no similar issues had been reported with its aircraft. It’s understood that had the problem not been resolved, Jetstar would have had to apply for an exemption from the Civil Aviation Safety Authority. That proved unnecessary.
Jetstar has cancelled the lowest percentage of flights of a domestic carrier according to the most recent data on airline performance for the Australian Competition and Consumer Commission.
Jetstar cancelled 5.1 per cent flights in March, compared to 5.2 per cent for Qantas and 5.4 per cent of Queensland-based Virgin, which was affected by the Cyclone Alfred in the month, the ACCC said.
The Qantas-owned economy airline had the second-highest on-time performance in March of 80.9 per cent, following Virgin Australia with 81.2 per cent.
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