TM 1-1520-238-10 Change 3 3-41 b. Navigate Mode. In the navigate mode (UTM or LATT/LONG position of the MODE selector switch), pow- er is applied to all system components, and all required outputs and functions are provided. Changes in present position are computed and added to initial position to de- termine the instantaneous latitude/longitude of the heli- copter. Destination and present position coordinates can be entered and displayed in UTM and latitude/longitude. At the same time, distance, bearing and time-to-go to any one of ten preset destinations are computed and dis- played as selected by the FLY TO DEST thumbwheel. c. Backup Mode. In this mode, remembered veloc- ity data are used for navigation. The operator can insert ground speed and track angle with the keyboard and the display in GS-TK position. This remembered velocity data can be manually updated through use of the keyboard and CDU DISPLAY selector switch in GS-TK position. When GS-TK values are inserted under these conditions, navigation continues using only these values. 3.14.7 Methods of Operation. Methods of operation are as follows: a. Window Display and Keyboard Operation. In all data displays except UTM coordinates, the two fields are the left and right display windows. In UTM coordinates displays, the first field of control is the center window and the second field is the combination of the left and right dis- plays. When pressing the KYBD pushbutton, one or other of the fields described above is under control. If it is not desired to change the display in the panel section under control, the pilot can advance to the next field of the dis- play panel by pressing the KYBD pushbutton again. The last character entered may be cleared by pressing the CLR key. That character may be a symbol or an alphanu- meric character. However, if the CLR key is pressed twice in succession, all characters in the field under control will be cleared, and that field will still remain under control. b. Data Entry. To enter a number, press the corre- sponding key. To enter a letter, first press the key corre- sponding to the desired letter. Then press a key in the left, middle, or right column corresponding to the position of the letter on the pushbutton.For Example: To enter an L, first press L, then either 3, 6, or 9 in the right column. The computer program is designed to reject unacceptable data (for example, a UTM area of WI does not exist and will be rejected). If the operator attempts to insert unac- ceptable data, the display will be blank after ENT is pressed. c. Starting Procedure. (1). Lamp Test 1. MODE selector switch – LAMP TEST. All display segments and indicator lamp should be on. 2. DIM control – Turn fully clockwise, then fully counterclockwise, and return to full clock- wise. All segments of the display should al- ternately glow bright, go off, and then glow bright. (2). Test. 1. MODE selector switch – TEST. NOTE Ignore the random display of alpha and numeric characters which occurs during the first 15 seconds. Also ignore test ve- locity and angle data displayed after the display has frozen. A successful test can- not be accomplished until HARS has completed BIT. If the MAL lamp lights during any mode of operation except LAMP TEST, the CDU MODE switch should be turned first to OFF and then to TEST to verify the fail- ure. If the MAL lamp remains on after re- cycling to TEST, enter the failure of the DNS on DA Form 2408-13–1 in the air- craft log book. After approximately 15 seconds, one of the following displays in table 3-13 will be observed in the left and right displays: