TM 1-1520-238-10 3-36 Change 3 Table 3-11. HARS Control Functions and Alignment Methods Method/Control How to Initiate Requirements/Function Effects On Accuracy Off Turns HARS off Normal Switch to NORM PPOS, MV and spheroid data entered through SP1 on data entry keyboard (DEK) prior to initiating alignment. Best accuracy attained by permitting completion of HARS alignment prior to starting the engines. Some degradation to alignment accuracy will occur if the engines are started prior to the HARS completing its alignment. This degradation will not occur if one engine is started and the rotor speed established at 100% within one minute and forty-five seconds after placing the HARS switch to NORM. Stored Heading Switch to FAST Helicopter shall not have been moved since HARS was shut down. Uses data from previous HARS alignment and flight. Accuracy is dependent on that data. Alignment time is the shortest of all methods (approximately 90 to 120 seconds). Accuracy is not affected by engine starts. FAST Switch to FAST Same as normal alignment. Least accurate method. Fastest method when stored heading alignment is not possible. Inflight Restart Switch to OFF, then to OPR AN/ASN-128 doppler MAL light must be OFF. Recycle doppler if necessary. If the HARS loses alignment in flight, the DASE will disengage. Switch the HARS OFF, then to OPR. After approximately 90 seconds, the HSI HDG flag will disappear and the DASE may be reengaged. The heading will appear to oscillate as the HARS attempts to align. The heading accuracy should be within 3 degrees after five minutes. Navigation performance will be degraded significantly. OPR Switch to OPR Operating mode. Switch shall be in OPR prior to moving the helicopter. 3.14.2 Required Navigation Data. The non integrated navigation system uses two components of data for prop- er operation: magnetic variation (MAGVAR) and spheroid (SPH). The HARS aligns with inertial North. MAGVAR is used to correct the inertial heading to one referenced to magnetic North. The symbolic heading tape, HSI, and RMI will all indicate magnetic heading. MAGVAR is en- tered in two places. Using the DEK, the present position MAGVAR on page 2 of Spare Position 1 (SP1) shall be checked and entered, if necessary, during the AFTER STARTING APU–CPG checklist. The second place that MAGVAR is input is in the DNS whenever coordinate data is entered. The spheroid is used to define the geographic reference frame that is used for the coordinate data. Spheroid is entered in 2 places. Using the DEK, the spher- oid on page 2 of SP1 shall be checked and entered, if nec- essary during the AFTER STARTING APU–CPG check- list. The second