Service Letter MTL-34-01: Navigation –
GPS-4000S Global Positioning System Software Update

Issued: May 14, 2020

Effectivity: Beechcraft King Air 90 Series, serial numbers LJ-2151 through LJ-2173; Super King Air B200GT, serial numbers BY-324 through BY-379; Super King Air B300, serial numbers FL-1140 through FL-1222; and Super King Air B300/B300C, serial numbers FM-76 through FM-85

Reason: To correct an anomaly with the UTC Time offset issue starting the week of June 11, 2023, in the Global Navigation Satellite System (GNSS) software of the GPS-4000S, CPN 822-2189-100. The LRU will not support Localizer Performance Vertical (LPV) approaches in the impacted region of +/- 20 degrees around 180 Degrees West Longitude.

Compliance – Recommended: This service document should be accomplished at a scheduled maintenance period or inspection.

Warranty: Eligible airplanes may qualify for parts and labor coverage to the extent noted in the Labor Hours and Material Availability sections of the document (posted in its entirety online at

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