Universal Avionics FMS GPS Rollover Software Update

Duncan Aviation Component Repair Services are now authorized to perform the FC06 FMS GPS week number rollover software update on the following Universal Avionics LRUs and applicable Service Bulletins (SBs):

LRU Part Number                                                       Service Bulletin

3019-XX-X0X                                                                3019.( )-34-3769

3116-XX-X11X                                                               3116.( )-34-3771

3017-XX-XXXX                                                              3017.( )-34-3768

3192-XX-X1110X                                                           3192.( )-34-3770

These SBs Mods apply to UNS-1Espw, UNS-1Lw, UNS-1Ew, and UNS-1Fw Universal FMS (Flight Management Systems).

These Mods are minor software changes to the GPS/SBAS (Global Positioning System/Satellite-Based Augmentation Systems) module intended to adjust the start date of the 1024-week cycle the internal GPS uses for date calculation.

The GPS week number rollover is a phenomenon that happens every 1024 weeks, or about 19.6 years. After the 1023^rd-week rolls back to zero, software that is not coded to anticipate the rollover may stop working or could cause the FMS to mistakenly display a date 20 to 40 years old.

With the current software, the correct date will be calculated up to May 31, 2025. With the new Mods software, the correct date will be calculated up to Dec 8, 2040.

Do Not Delay! Installation of these Mods is highly recommended.

As the May 31, 2025, rollover deadline approaches, the demand for the software upgrade will get high, and the available capacity and schedules to perform these Service Bulletins will become very tight.

If your Universal FMS needs repairs we recommend that you have this SB installed at that time. Universal Avionics will not cover the cost of labor or the removal and replacement of units but will pay to have the unit returned if it is still under warranty.

In the United States, the modifications described in these SBs may only be installed by Universal Avionics or Duncan Aviation Component Repair Services. Contact a Duncan Aviation Customer Account Rep to schedule your service.