TM  1-1520-240-10 3-3-14            from the No. 2 (No.1) instrument bus through the NAV PLT (COPLT) HSI circuit breaker. 3-3-34.  Controls and Indicators - Horizontal Situa- tion Indicators.  (fig, 3-3-6) CONTROLS/ INDICATOR FUNCTION Compass Card The compass card is a 360_ scale that turns to display heading data obtained from the gyro magnetic compass (AN/ASN-43). The helicopter headings are read at the up- per lubber line. Bearing Pointer No. 1 The pointer operates in con- junction with doppler or mixed GPS/DOPPLER. With Doppler Only, indicates magnetic bearing to doppler destination. With mixed GPS/Doppler, indicates magnetic bearing to GPS destination. (With GPS Only, bearing information is not available.) Bearing pointer No. 2 The pointer operated in con- junction with selected VOR or ADF receiver. The pointer is read against the compass card and indicates the mag- netic bearing to the VOR or ADF station. Course Deviation Indi- cator. This indicator indicates lateral deviation from se- lected VOR course or GPS/ Doppler computed course or heading in the case of FM homing. When the helicopter is flying to correct course, the course indicator will be aligned with the course pointer and will be centered on the fixed aircraft symbol. The two dots on either side of the indicator indicate amount of course deviation. One dot displacement is equivalent to 5_ off VOR or GPS/Doppler and 1 1/4 de- gree off localizer course. These displacements do not apply to FM homing. CRS Knob Course Indicator Course Pointer The COURSE indicator and course pointer operate in conjunction with the course selected (CRS) knob, and allow the pilot to select any VOR course. The course pointer turns with the com- pass card and will be aligned with the with the CONTROLS/ INDICATOR FUNCTION lubber line when the helicop- ter heading is the same as the selected course. Range indicator Digital distance display in ki- lometers (KM) to destination set on GPS Control Display Unit (CDU) (para. 3-3-36) or doppler control FLY-TO- DEST thumbwheel (para. 3-3-12). HDG Knob Heading select (HDG) knob operates in conjunction with the heading bug. It allows the pilot to select any one heading. With CMD SEL (fig. 3-3-6) selected on the HSI MODE SELECT panel, the AFCS (chapter 2) will turn the helicopter to and main- tain the selected heading. HDG Flag The HDG flag is in view when the signal from the gyro magnetic compass is unreliable or power to the in- dicator is lost. To-From Arrow To-from arrow indicates that the helicopter is flying to or away from the selected VOR. NAV Flag The NAV flag turns with the compass card. The flag will retract from view when a re- liable VOR, GPS/Doppler or FM homing signal is being applied to the instrument. Aircraft Symbol Corresponds to longitudinal axis of the helicopter; shows helicopter position and heading relative to the se- lected course. Glide Slope Pointer Displays glide slope position relative to the helicopter or FM homing signal strength. When pointer is above cen- ter, helicopter is below glide slope, conversely when pointer is below center, heli- copter is above glide slope. Increasing homing signal strength is shown by pointer rising. decreasing signal strength is shown by pointer falling. Glide Slope (GS) Warning Flag Indicates loss of or an unre- liable glide slope or FM homing signal.