Central European budget carrier Wizz Air has recorded a decline in spurious terrain warnings since implementing defensive crew procedures against GPS spoofing and interference earlier this year.
Wizz Air Hungary flight-data monitoring manager Akos Steigervald detailed the carrier’s experience during the annual European Union Aviation Safety Agency conference in Budapest at the end of October.
He says the carrier has had to mitigate pilots’ potential loss of trust in aircraft systems, including ‘pull up’ alerts from ground-proximity warning systems.
While the carrier had its own processes to help mitigate risks, Steigervald says the new supplementary procedure in the flight crew operating manual, released at the end of June, is demonstrating positive results.
Steigervald says the airline initially began noticing GPS jamming in 2020, mainly on outbound services from European bases to Dubai and Abu Dhabi, although the impact was relatively small.
But increasing occurrences on these routes, and the interdependency between GPS equipment and other aircraft systems, subsequently resulted in other effects including nuisance alerts from the ground-proximity warning system.
There was a “substantial” rise in events last year, says Steigervald, with effects spreading to the eastern Mediterranean, the Black Sea and southern Caucasus, and most recently the Baltic states and Poland.
The situation spurred Wizz to begin analysing occurrences through flight-data monitoring and, this year, it set up a periodic review of spurious ground-proximity alerts.
Steigervald says the carrier has found other effects including map shifts – which have been observed on the ground before departure – as well as nuisance ‘runway too short’ alerts from on-board performance tools, and inconsistent information on wind speed and direction.
“Since we have several bases on the affected network, we have a lot of data to rely on and analyse due to the high traffic,” he adds.
Flight-data monitoring enabled Wizz to examine critical-exceedance events, he says. The carrier found that trend lines for such events involving, and not involving, GPS interference started to “drift apart” last year.
This divergence indicated that interference-related events accounted for about 50% of overall critical exceedances.
Since November 2023, says Steigervald, the airline has not recorded a single month in which terrain warnings have not exceeded the combined total of those in 2021 and 2022.
But the new procedure – which has been simplified and centralised – has progressively reduced occurrences over the course of July, August and September.
“[We have a] long way to go still but we’ve managed to regain control and, with the implemented actions, we’re on a good track now,” he states.
