TM 1-1510-225-10 3B-163 Table 3B-98.  System Failure Indications  (Continued) SUBSYSTEM FAILURE INDICATION POSSIBLE EFFECTS Bit 12 Antenna Fault V/UHF   radio   receive   or   transmit   capability   may   be inoperative or have impaired capability. Bit 13 Radio Fault V/UHF   radio   may   be   inoperative   or   have   impaired capability. Bit 14 Equipment Fault V/UHF   radio   may   be   inoperative   or   have   impaired capability. Verify other faults for functional degradation. Bit 15 MIL-STD -1553 Terminal Status V/UHF  radio  may  be  unable  to  communicate  on  the 1553 bus. Bit 16 V/UHF Radio Subsystem Status V/UHF   radio   may   be   inoperative   or   have   impaired capability. BUS MIL-STD -1553B Bus Status NGO-A:  V/UHF radio is not responding on the A bus. NGO-B:  V/UHF radio is not responding on the B bus. NGO-T:      V/UHF   radio   is   not   responding   on   either 1553 bus. w.  Miscellaneous Functions. (1)   Miscellaneous  Functions.  The   FMS-800 also   provides   the   following   functions   that   are   not covered in the previous sections: (a)   Timers. Three independent stopwatch   lap   counters   are   available   complete   with time-out annunciations. (b)   Model   Aircraft.    The  model  aircraft inserts heading, altitude,  wind,  and  true  airspeed  data into the navigation equations in order to provide a flight simulation capability. (2)   Timer   Function.      Access   the   timers   by pressing the   TIMERS  line  select  key  on  the  Index  1 page.  The three timers can be used independently to display   elapsed   time   (counting   up   to   23:59:59)   or countdown  to  00:00:00.    They  can  be  stopped  at  any time.      Figure   3B-134   and   Table   3B-99   shows   an example of how to use the timer function. (3)   Model    Aircraft    Function.        The    model aircraft is a mission simulation  capable  of  following  all flight   plan   maneuvers   to   include   holding   patterns, vertical navigation, and intercepts.  The model aircraft can   only   be   operated   when   the   weight   on   wheels discrete  indicates  the  aircraft  is  on  the  ground.    The ability  of  the  model  to  correctly  navigate  is  limited  to the  mid  latitude  (<  70)  regions  and  airspeed  above 10 knots.      Higher   latitudes   and   low   airspeeds   may produce unexpected results in system response due to instabilities in the model.