TM 1-1520-238-10 Change 4 4-17 4.17 WAYPOINT/TARGETING. / NOTE If software is installed go to paragraph 3.16 for Waypoint/Targeting system descrip- tion and operation. Waypoint/targeting functions are performed solely by the CPG. The pilot cannot actively participate. Four functions can be implemented. These are: preflight, storing, posi- tion update, and cueing. 4.17.1 Waypoint/Targeting Data Entry. The way- point/targeting function requires certain data. The data is input using both the TGT and SP1 positions on the DEK rotary switch. The data entered under SP1 is displayed as a menu with two pages. They are: TIME: HH: MM: SS PPOS: 11S QG 5551 5221 ALT: +AAAA’ HG: 29.92IN. SPH:CL6 MV: EO13.8 DEG DOPP BIAS: L0.0 DEG HEADING (MAG): 000.0 DEG SPH:CL6 MV: EO13.8 DEG HEADING (MAG): 000.0 DEG a. Data Entry. To enter data input the first character of the desired parameter. The cursor will jump to the first digit position of the data, then input the full data required. On completion the data will be automati cally entered. NOTE The LAT/LONG conversion process within the FCC contains non–linear transformation errors in accordance with the table below: Latitude Possible Error 0 to 34 Less than 2 meters 35 to 44 Less than 50 meters 45 to 54 Less than 1100 meters 55 to 63 Less than 2000 meters 64 and up More than 2000 meters (1) FCC Present Position Data. The FCC pres- ent position (PPOS) data are used only for the initial align- ment of the HARS when the helicopter is on the ground. The present position shall be entered prior to a normal or fast alignment of the HARS. It is not required for a stored heading alignment or inflight restart. The accuracy of the present position input should be within 500 – 750 meters, straight line distance, from the actual location. Inflight this display will periodically update reflecting the doppler pres- ent position. The doppler display updates at a substantial- ly higher rate than the PPOS display, consequently there may not be any correlation of the doppler and PPOS dis- play in forward flight. This is normal and does not indicate a problem condition. If at any time ?? appear following the PPOS data, as shown in the example, the FCC is rejecting the doppler navigation data as being in error. This may be an indication of doppler malfunction or that the doppler has not been updated recently. The displayed PPOS data, in this case, will then reflect the best computed present position based on HARS velocity data. (2) Altitude and Altimeter Data. The altitude and altimeter setting data are to be used in the following manner: Altitude above mean sea level shall be entered when the aircraft is on the ground. The value is deter- mined from referring to navigational charts or by tactical map study. The Fire Control System will compute the cor- responding altimeter setting. The altimeter setting shall be entered when the aircraft is in flight. The altitude display may be observed in flight; if an error exists in the dynamic altitude display when compared to the aircraft barometric altimeter, the altimeter setting should be entered. The al- timeter setting can normally be obtained from a local air traffic control agency. In the event of a failure of the air data sensor, question marks, ??.??, will be displayed in the altimeter setting display. The fire control system will at- tempt to derive the aircraft altitude above mean sea level by adding radar altitude to the last valid altitude value dis- played. The altitude value should then be periodically up- dated in flight. The altitude value computed from radar al- titude is accomplished based on standard atmosphere. (3) Time Display Functions. The TIME display functions only when power is applied to the fire control computer. The TIME display is not part of the backup bus controller software. The TIME display will increment from whatever time value is entered; on initial power up the TIME value is zero. If a TIME value of 00:00:00 is input, the TIME display will function as an elapsed time clock. The TIME display is a twenty–four hour clock with an ac- curacy of plus or minus 1 second while running.