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Are You Ready? GPS Week Number Rollover is Approaching!

Jan 28, 2019
Amanda Grizzard, Field Service Engineer

Universal Avionics UNS1-Ew

You may have heard of an upcoming event referred to as "GPS Week Number Rollover," which will occur on April 6, 2019. On this date, Global Positioning Systems (GPS) receivers with a specific time keeping limitation will be impacted as well as the systematic equipment in which they are installed. This includes numerous aircraft navigation systems, and specifically, some Universal Avionics Flight Management Systems (FMS). To address this GPS time-keeping issue, the GPS sensor may need to be updated, however the specific correction will depend on the type of FMS you operate.

Universal Avionics GPS equipment, to include FMS with internal GPS sensors that are not Satellite-Based Augmentation System (SBAS)-capable, may require an update. Affected systems may no longer be capable of performing GPS approaches without modification, while other systems may simply require manual date adjustments.

Newer GPS receivers – like those in the SBAS-FMS which are Automatic Dependent Surveillance-Broadcast (ADS-B) Out approved – have a different GPS time configuration and are therefore not impacted.

For more information and for instructions that will help you identify if your FMS is affected, consult UA Service Bulletin (SB) No. 3719, "GPS Product Line Week Rollover Impact." Service information is available through UniNet, our online customer portal.

There are many online resources describing the GPS Week Number Rollover, however we found this article from masterclock.com to be especially useful.

Additional Information

For more information, please contact UA Customer Support at +1 520 573 7627 · 800 595 5906 or customersupport@uasc.com.

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