Duncan Aviation is warning operators of aircraft equipped with certain Univeral Avionics flight management systems (FMS) to update the FMS software before May 31 or face possible service interruptions. Delaying the upgrade may also mean vying for available slots at avionics shops, the company added.

According to Duncan Aviation, the FC06 software update applies to UNS-1Espw, UNS-1Lw, UNS-1Ew, and UNS-1Fw FMSs. It changes coding for the GPS/SBAS module “to adjust the start date of the 1024-week cycle the internal GPS uses for date calculation.”

“The GPS week number rollover occurs every 1,024 weeks, or about 19.6 years. After the 1,023rd week rolls back to zero, software that is not coded to anticipate the rollover may stop working or 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 [FC06] software, the correct date will be calculated up to Dec. 8, 2040.”

Universal FMSs needing repairs can be updated during the repair process. Duncan Aviation Component Services or Universal Avionics can accomplish the applicable service bulletin update.