TM 1-1520-238-10 Change 3 3-49 d. Test Mode. The DNS and CDU have both Con- tinuous and On Command FDLS tests. The DNS continuous test checks the doppler anten- na (RTA), and doppler signal data converter computer (SDCC). The CDU monitors its own internal functions and the dedicated 1553B mux bus between the CDU and DNS SDCC. If a fail- ure is detected by the Continuous test, the CDU will display the prompt FDLS on line 6 of the NAV top level page. The CPG can then display system status by pressing the FDLS fixed action button (FAB). The CPG can initiate the ON Com- mand test from the FDLS page. The On Com- mand test initiates a full DNS subsystem compo- nent test. If no failures are detected, the CDU will display the pitch, roll, and inertial heading, in degrees, currently being used by the DNS. The pitch and roll angles will reflect the actual orien- tation of the helicopter on level ground, pitch will be approximately 4.5 to 5.5, and roll should be about 0.0. If the helicopter has a lean due to cy- clic or pedal inputs, this will be reflected in the roll angle displayed. The heading value dis- played is the inertial heading of the helicopter; HSI/RMI heading plus or minus the magnetic variation. 3.15.2 CDU Displays. The CDU display architecture is organized into page formats. Each page consists of 8 display lines. The first seven are 22 characters wide for displaying data. The bottom (eighth) line is 21 characters wide and is a scratchpad for entering or editing data. Indi- vidual pages may display navigation data, display failure messages, or indicate selectable functions. The CDU dis- plays are categorized into 5 basic page formats: NAV top level, ADMIN, FDLS, HBCM, and FPLN. The CDU dis- play will automatically revert back to the NAV top level page based on two basic rules: Rule 1. – The CDU will revert to the NAV top level page automatically from the ADMIN or any of the FPLN (way- point dictionary pages after 30 seconds if there are no characters in the scratchpad. The 30 second timer is reset each time a FPLN page is scrolled with the Up/Down ar- row when the scratchpad contains no data. Remember: If the scratchpad contains any data the display will NOT au- tomatically revert back to the NAV top level page. Rule 2. – The CDU will revert to the NAV top level page automatically from the ADMIN page 3 seconds after pressing any of the following (VAB)s: PWR ON or PWR OFF, BACKUP, MODE UTM or MODE L/L, and DISPL KPH or DISPLKTS. If the HBCM VAB on the ADMIN page or FDLS FAB is pressed the CDU will NOT revert automatically back to the NAV top level page. The NAV top level page can be manually selected at any time from any page by pressing the NAV FAB. a. NAV Top Level Page. The NAV top level page (fig 3-13) will be displayed approximately 30 seconds after aircraft electrical power is applied. No data will be dis- played until the DNS power is turned on. The DNS is pow- ered by pressing the ADMIN VAB and then pressing the PWR OFF VAB on the ADMIN page. The DNS indicates a failure if it is powered and the HARS is OFF or in the first 90 seconds of alignment. When the DNS is powered, the NAV top level page (fig 3-14) will display the following: M01-218-1 FLY TO DEG GS KPH TKA TGT PPOS var sph BRG DEG ADMIN DIST TTG Figure 3-13. Power Up Display, NAV Top Level – DNS PWR OFF M01-218-4 FLY TO 1 000 DEG GS OKPH TKA TGT 18 PPOS 12S VN 3262 0377 var E12.3 sph CL6 BRG 324 DEG ADMIN DIST TTG - - - - - -.- KM MEMORY Figure 3-14. NAV Top Level Page – PWR ON