GPS “Week Number” Rollover


On 6 April 2019, the “week number” broadcasted by GPS satellites will be reset to zero. Some panel mounted GPS navigation systems and portable units require a software update to ensure proper functionality.

Many GPS receivers are prepared for the rollover and will continue to work without problems. Others need a firmware update so that they don't suddenly behave as if they've made a leap back to 21 Aug 1999. 

In order to mitigate any safety risk related to the GPS week rollover, EASA recommends taking the following proactive measures: 

  • Ensure that the latest software update is installed on potentially affected GPS receiver(s)

  • Request information from the GPS receiver manufacturer regarding its robustness against the GPS week rollover

  • If possible, perform tests that simulate the GPS week rollover, e.g. using a GPS simulator

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