GTN 625/635/650 TSO Installation Manual 190-01004-02Page 6-56 Rev. F6.10.10 Altitude Encoder or Air Data Computer CheckThe GTN can receive altitude data from an externalsource. This check verifies that the GTN is receivingdata from these sources. Ensure that the GTN ispowered on and in configuration mode. If thefollowing steps do not perform correctly, check theelectrical connections () and configuration setup(Section 6.6.2) for the interfaced Altitude Encoder/ADC.1. Access the Main Data Inputs page, as shownin Figure 6-58, by touching the ‘Main DataInputs’ key on the GTN Diagnostics page.2. Touch the ‘Down’ key to scroll to the Pressure Altitude data display.3. If there are multiple altitude sources providing data to the GTN, remove power from all but onesource.4. Verify that Pressure Altitude is being displayed and agrees with the active altitude source.NOTEAfter applying power to an altitude source it may take several minutes to warm up. Duringthe warm-up period the Pressure Altitude display on the GTN will be dashed out.5. If there are multiple altitude sources, remove power from the currently active source and applypower to another source that has not been checked.6. Repeat steps 2-4 until all available sources have been checked.6.10.11 AHRS/IRU Interface CheckThe GTN can receive heading data from an external source. This check verifies that the GTN is receivingdata from these units. Ensure the GTN is powered on and in configuration mode. If the following steps donot perform correctly, check the electrical connections and configuration setup for the interfaced AHRS/IRU.1. Access the Main Data Inputs page, as shown in Figure 6-58, by touching the ‘Main Data Inputs’key on the GTN Diagnostics page.2. Scroll to the Heading data display.NOTEIf a Sandel EHSI or an ARINC 429 EFIS is also installed, ensure that it is turned off sothat it does not supply heading to the GTN. Verify that the HDG field displays validheading data.3. Remove power from the heading source and verify that the magnetic heading field is dashed out.Figure 6-58. Main Data Inputs Page
