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Upside Down FMS Database Cards Cause Unexpected Squawks

November 2016

We work on many Honeywell GNS-XLS in the Duncan Aviation avionics and instruments shop on a regular basis. It is a popular FMS (Flight Management System) used on many business jet make/models in service today. At times, we receive these units in with squawks ranging from RAM Failure to Blank Display. After inspecting the units, we often discover that the NDB (Navigation Database) card (PCMCIA card) is installed upside down. 

In the case of Blank Display, the majority of the time the removal of the NDB card allows the display to come back up, but the unit may still not function correctly. 

The improper installation on the NDB card could possibly damage the CPU module in the unit, prevent the database from updating, cause damage to the NDB card itself, or cause other communication failures within the unit. 

The re-installation of software may fix the unit, while at other times the CPU board may need to be replaced. 

Remember only the PRNAV (Precision Area Navigation) units (P/Ns 17960-0103-xxxx and 17960-0204-xxxx) require that the NDB card remain in the unit. We recommend that the NDB card be removed after update from all other units.

The easiest way to verify that you are installing the NDB card correctly in any GNS-XLS, GNS-XL or data loader is to have the NDB card lock tab be on the same side as the ejection button of the device.

Please feel free to contact Duncan Aviation for troubleshooting assistance in this matter.