TM 1-1510-225-10 3A-36 Figure 3A-15. EHSI 360° Map Symbol Definitions b. EHSI Controls, Indicators, and Functions. Refer to Figure 3A-16. (1) Course/Desired Track Digital Display. The course/desired track digital display is an alphanumeric display located in the upper left comer of the EHSI. It displays CRS followed by the selected navigation course in degrees. The CRS knob on the EFIS control panel rotates the course pointer about the compass scale and sets the course/desired track digital display. (2) Drift Angle Indicator. The drift angle pointer is a triangular pointer that is generated by the GPS and rotates around the outside of the compass scale. Referenced to the lubber line, the drift angle pointer displays drift angle left or right of aircraft heading. With respect to the compass scale, the drift angle pointer displays actual ground track. Drift angle pointer information is provided by the GPS and will be displayed only when the GPS is selected as the primary navigation source and valid information is present. If the pointer information becomes invalid, it will be removed from the display. (3) Directional Gyro Mode Or Source. The directional gyro mode or source annunciator located to the left of the lubber line indicates whether heading information is being supplied to the EFIS from directional gyro number 1 or 2 (DG1 or DG2), or if the system is operating in the free gyro mode (FDG). (4) Lubber Line. Aircraft heading is read from the compass card under the lubber line. (5) Heading Marker. The heading marker is positioned on the compass card by rotating the heading select knob located on the EFIS control panel. (6) Heading Miscompare Indicator. The yellow double-ended heading miscompare arrow will be displayed over HDG to the left of the lubber line on the EHSI if heading 1, 2, and cross-side differ by more than 6 up to 6 of bank and by more than 20 above 6 of bank. If bank information is not available the heading miscompare will be displayed if heading differs by more than 20. The heading miscompare symbol will also be displayed if the failure warning flags differ. Heading miscompare will not be performed if sources are not all magnetic or all true. (7) Primary Navigation Source Range (Or Held DME Distance). The range display for the primary navigation source or DME hold distance is displayed in the upper right comer of the EHSI. (8) Groundspeed or DME Hold Frequency. Displays groundspeed to 999 KTS or DME hold frequency. (9) Time To Go. Displays time to station up to 8:31 (H:MM universal format). Time to station is displayed immediately below and at the same time as groundspeed.
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