By: Prem Mahendranathan
China Aviation Review reported of grounding 15 Boeing 787s in China due to GPS 20 years rollover issue.
The tweet read; “Multiple Boeing 787s in China experienced GPS 20 years rollover issue. Some aircrafts have to be grounded waiting for an update.”
So what is this rollover issue?
The GPS systems uses atomic clocks on satellites to set the GPS time. When Global Positioning System was first implemented, time and date function was defined by a 10-bit number., means GPS date is a “week number,” and is transmitted as a 10-bit field in navigation messages and rolls over or resets to zero every 1,024 weeks.
That means, the system starts counting at week zero and reset when they hit week 1,024. The first count started on January 6th, 1980, and the first reset took place on August 21st, 1999. Then the next calendars reset was at 7:59 p.m. EDT on Saturday April 6th 2019.
When the date passed, most of the new system worked without any issue, but the older version of GPS systems or ones that hadn’t been updated reported issues.
However, it was reported that not all Boeing 787s are affected.
Multiple Boeing 787s in China experienced GPS 20 years rollover issue. Some aircrafts have to be grounded waiting for an update. pic.twitter.com/IEFF2GHIt2
— ChinaAviationReview (@ChinaAvReview) April 7, 2019