TM 55-1510-219-10 VOR 1 VOR 1 controls copilot's HSI. VOR 2 VOR 2 controls copilot's HSI. NAV-A switch Applies VOR audio to respective headsets. MKR  BCN HI- Controls  sensitivity  of marker LO switch beacon receiver. c. Operation. (1) Turn-on. 1.    Insure  aircraft  DC  and  AC  power  is on. 2.    AVIONICS MASTER POWER switch (overhead panel) ON. 3.    Frequency controls (NAV panel) Set for both receivers. 4.    VOL knobs (NAV panel) Turn clockwise   to   activate   sets,   adjust volume. 5.    NAV  A,  audio  switch  ON.    Confirm proper signal, then OFF. 6.    Confirm proper indications RMI and HSI. (2) Normal operation. (a)    Pilot,  copilot  COURSE  INDICATOR switches  (instrument  panel):  Select VOR source. (b)    To  determine  course  to  station  on pilot's HSI: Rotate course knob until course deviation pointer is centered and TO-FROM flag reads TO. (c)    To   determine   bearing   from   station on  pilot's  HSI.:  Rotate  course  knob until    course    deviation    pointer    is centered  and  TO-FROM  flag  reads FROM. (d)    To  determine  course  to  station  on RMI.:    Select    VOR,    verify    needle points course to station. (3) Localizer (LOC) operation. 1. VOR  frequency  knob  (NAV  panel) Select frequency. 2. Pilot's, copilot's COURSE INDICATOR    switches    (instrument panel) Select VOR source. 3. Course   deviation   bar   (HSI)   Steer aircraft to center bar. (4) Glideslope operation. 1.    Frequency    selectors    (NAV    panel) Set desired localizer frequency. 2.    VOR switch (instrument panel) Select VOR source. 3.    Glideslope pointer (HSI) Fly aircraft to center pointer. (5) Self-test. (a) NA V 1. 1.    Frequency select knob (NAV panel) Select a VOR frequency. 2.    NAV      TEST      switch   (NAV   panel) Press and hold. 3.    RMI      Observe   that   single   needle indicates  approximately 005°. 4.    VOR/LOC flag Check that flag is out of view. 5.    TO/FROM pointer Check that pointer indicates TO. 6.    HSI course deviation bar Check for centered bar. 7.    Marker  beacon   lights  Check that all  three  lamps  are  illuminated  and flickering  at  approximately  a  30  Hz rate. 8.    VOR  frequency  knob  (NAV  panel) Select a LOC frequency. 9.    VOR/LOC flag Check that flag is out of view. 10.    HSI course deviation bar Check that bar indicates a deflection of approximately     one     dot     right     of center. 11.    HSI  glideslope  pointer  Check that pointer    indicates    a    deflection    of approximately one dot below center. 12.    Marker    beacon    lights    Check  that all  three  lamps  are  illuminated  and flickering  at  approximately  a  30  Hz rate. (b) NA V 2.  All NAV 2 self-test procedures are the same as  those  used  for  NAV  1,  with    the exception    of    the    marker    beacon test.      There   is   no   marker   beacon receiver in the NAV 2 system. 3-28