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Aviation Alerts and Advisories

Service Alert 071016-00: Sandel SN3308 When Coupled With A Garmin GPS 400W, GNC 420W, GNS 430W, GPS 500W, or GNS 530W


All GNS 400W/500W products installed with a Sandel SN3308 EHSI


The Sandel model SN3308 EHSI has a feature called AUTO SLEW. When this feature is enabled and GPS is the selected navigation source, the SN3308 will automatically rotate the course pointer to the desired course sent by the 400W/500W Series unit. When the SN3308 is given a new course from the GPS, it slews to the new commanded course.

When NAV (VLOC) is the selected navigation source for the SN3308, course selection is always manual. If the navigation source is switched from GPS to NAV (VLOC) before the SN3308 has completed slewing to the new course, the course pointer will stop and may indicate a heading that will not intercept the desired course. Setting the ILS CDI CAPTURE to ‘Auto’ on the CDI/ALARMS AUX page causes the Garmin 400W/500W navigation system to automatically change to VLOC as the navigation source when
using GPS navigation to intercept an ILS or localizer approach.


The Pilot should always verify the selected course on the SN3308 after any change to the navigation source (GPS-VLOC/NAV).

Setting the ILS CDI CAPTURE to ‘Manual' on the CDI/ALARMS AUX page of the Garmin 400W/500W unit is recommended to disable the automatic switching of the navigation source (as when the ILS CDI CAPTURE setting is ‘Auto’).

Download 071016-00