TM 1-1510-225-10 3C-21 result.      The   number   on   the   numeric   entry   line   is cleared. (k)  Multiply Operation. When the SP key is pressed, this operation multiplies the number on the numeric entry line by the number on the third line and replaces  the  number  on  the  third  line  with  the  result.   The number on the numeric entry line is cleared. (l)   Divide Operation. When the (,) key is pressed, this operation divides the number on the third line   by   the   number   on   the   numeric   entry   line   and replaces  the  number  on  the  third  line  with  the  result.   The number on the numeric entry line is cleared. (m)  Forward Space and Backspace Keys. These keys can be used to change the position of the separator    on    the    numeric    entry    line    in    order    to decrease  or  increase  the  extent  of  the  numbers  that can be entered into the numeric entry line.  Each time the   ®    key   is   pressed,   the   separator   moves   one position  to  the  right  and  replaces  any  character  that may have been in that location.  The separator cannot be  moved  beyond  column  19.    This  allows  space  for the entry of at least one digit and a sign. Each time the   ¬   key  is  pressed,  the  separator moves   one   position   to   the   left   and   replaces   any character  that  may  have  been  in  that  location.    The separator  cannot  be  moved  beyond  column  2.    This allows space for the asterisk in column 1. (n)  Home Function.  When the HC key is pressed,   the   separator   is   returned   (homed)   to   the standard  position  (column  11)  on  the  numeric  entry line.  Any character that was present in that location is replaced by the separator. (o)  Arithmetic Results. When an arithmetic  operation  (+,  –,  x,  ÷)  is  performed  on  two numbers and the result is greater than the number of digits    allowed    to    the    right    of   the   separator,   the message   OVERFLOW   will   display   on   the   third   line instead  of  the  result.    When  an  arithmetic  operation (+, –, x,  -) is performed on two numbers, with at least one containing a decimal point, the result will include the  sign  and  all  the  digits  to  the  left  of  the  decimal point  and  as  many  digits  to  the  right  of  the  decimal point as can fit into the remaining space.  Those digits that cannot be fit in are truncated, so that no round off occurs in the least significant digit in column 21. (p)  Clear  Function.    When  the   D  key  is pressed,   all   the   data   on   the   page   is   cleared,   the asterisk is set to column 1 on the numeric entry line, and   the   separator   is   set   into   the   standard   position (column 11) on the numeric entry line. (q)  Mode   Function.      When   the   MODE key is pressed during the calculator mode, the numeric entry   line   is   cleared,   including   the   separator;   the asterisk is cleared only if it is on the numeric entry line; the  cursor  is  positioned  to  the  start  of  the  data  entry region; and the mode is changed to data entry.  When the MODE key is pressed again, the cursor is removed from the screen; the separator displays in the standard position   (column   11   of   the   numeric   entry   line);   the beginning of stack is returned to the numeric entry line unless   it   was   already   present   elsewhere;   and   the mode is changed to calculator. 3C-17.  HORIZONTAL SITUATION INDICATOR. a.     Description. The Horizontal Situation Indicator (HSI) combines numerous displays to provide a  map-like  presentation  of  the  aircraft  position.    The indicator   displays   aircraft   displacement   relative   to VOR, localizer, glideslope beam, TACAN, and heading as   selected   by   the   HSI   selector   switches   located outboard  of  each  HSI  with  respect  to  magnetic  north.   Any warning flag in view indicates the respective (NAV or   HDG)  information  is  unreliable.    Refer  to  Figure 3C-10. NOTE Aircraft   HSI   circuitry   modified   by   Beech Service     Instruction     No.     C-12-0118     will operate    as    follows:    In    addition    to    the standard   warning   flag   conditions.      If   a TACAN circuitry 26 Vac power loss occurs and   TACAN   is   selected,   the   HSI   bearing pointer  (OSA  only)  will  drive  to  the  Park position  and  the  NAV  flag  (ANG  and  OSA) will drop into view. Deviation  relays  of  the  VOR/LOC  and  TACAN systems  are  monitored  by  a  failure  warning  system.   During ILS operation, the GLS -1 and GLS -2 relays are also monitored.  The  HSI NAV and/or  VERT flags will display when a relay or relays of the system selected for display fails. b.    Controls, Functions, and Indicators. (1)   Distance Display – Provides digital displays    of    DME    or    TACAN.        DME    and    TACAN distance is displayed in 1/10-mile increments. (2)   Rotating   Heading   Dial   –   Displays  gyro stabilized   magnetic   compass   information   on   a   dial which  rotates  with  the  aircraft  throughout  360.    The azimuth ring is graduated in 5 increments. (3)   Heading  Warning  Flag   –  When  in  view, indicates the heading information is unreliable.