TM 1-1510-224-10 warning  horn  circuit  is  protected  by  a  5-ampere  circuit breaker,  placarded  LANDING  GEAR  HORN,  located  on the overhead circuit breaker panel (fig.  2-9). g. Landing  Gear  Safety  Switches.    A  safety switch  on  each  main  landing  gear  shock  strut  controls the   operation   of   various   aircraft   systems   that   function only during flight or only during ground operation.  These switches  are  mechanically  actuated  whenever  the  main landing  gear  shock  struts  are  extended  (normally  after takeoff)   or   compressed   (normally   after   landing).      The safety    switch    on    the    right    main    landing    gear    strut deactivates    the    landing    gear    control    circuits,    cabin pressurization  circuits,  and  the  flight  hour  meter  when the    shock    strut    is    compressed.        This    switch    also activates  a  downlock  hook,  preventing  the  landing  gear from   being   raised   while   the   aircraft   is   on   the   ground. The hook, which unlocks automatically after takeoff, can be   manually   overridden   by   pressing   down   on   the   red button, placarded   DN  LOCK  REL,  located  adjacent  to the  landing  gear  handle  (fig.    2-8).    If  the  override  is used,     the     landing     gear     warning     horn     will     sound intermittently  and  two  parallel-wired  red  indicator  lights, located  in  the  landing  gear  control  switch  handle,  will illuminate,  provided  the    BATTERY   switch   is   on.      The safety switch on the left main landing gear strut activates the left and right engine ambient air shut-off valves when the strut is extended. h. Landing Gear Alternate Extension. WARNING After    an    emergency    landing    gear extension   has   been   made,   do   not move   any   landing   gear   controls   or reset any switches or circuit breakers until   the   aircraft   is   on   jacks.      The failure  may  have  been  in  the  gear-up circuit, which could cause the gear to retract   while   the   aircraft   is   on   the ground. If   for   any   reason   the   three   green GEAR  DOWN  indicator  lights  do  not illuminate (e.g., in case of an electrical    system    failure),    continue pumping  until  sufficient  resistance  is felt  to  ensure  that  the  gear  is  down and  locked.    Do  not  stow  the  hand pump   handle.      Stowing   the   handle will release hydraulic pressure.  If the three   GEAR   DOWN   indicator   lights are  not  illuminated,  the  landing  gear downlocks  may  not  be  engaged  and hydraulic  pressure  may  be  the  only thing holding the landing gear down. An   extension   lever,   placarded   LANDING   GEAR ALTERNATE   EXTENSION,    is    located    on    the    floor between  the  crew  seats.    Manually  pumping  the  lever lowers  the  landing  gear.    The  hydraulic  pump,  which  is utilized  to  manually  lower  the  gear,  is  located  under  the floor. To engage the system, pull  the  LANDING  GEAR CONTROL   circuit   breaker,   located   on   the   overhead circuit breaker panel (fig.  2-9), and ensure that the  LDG GEAR  CONTR  handle  is  in  the   DN  position.    Remove the  extension  lever  from  the  securing  clip  and  pump  the lever  up  and  down  until  the  three  green   GEAR  DOWN indicator   lights   illuminate.      As   the   handle   is   moved, hydraulic:    fluid  is  drawn  from  the  hand  pump  suction port   of   the   power   pack   and   routed   through   the   hand pump  pressure  port  to  the  actuators.    After  an  alternate extension of the landing gear, ensure that the extension lever is in the full down position prior to stowing the lever in   the   retaining   clip.      When   the   lever   is   stowed,   an internal  relief  valve  is  actuated  to  relieve  the  hydraulic pressure in the pump. After    a    practice    alternate    extension,    stow    the extension  lever,  reset  the   LANDING  GEAR  CONTROL circuit    breaker,    and    retract    the    gear    in    the    normal manner with the landing gear control handle. i. Tires.    The  aircraft  is  equipped  with  dual 22  x  6.75  x  10,  10  ply  rated,  tubeless  rim-inflation  tires on  each  main  gear  and  a  22  x  6.75  x  10,  8  ply  rated, tubeless tire on the nose wheel. j. Nose     Wheel     Steering     System.          The aircraft is maneuvered on the ground by the nose wheel steering  system.    Direct  linkage  from  the  rudder  pedals (fig.  2-10) to the nose wheel steering linkage allows the nose wheel to be turned 12 to the left of center or 14 to the  right.    When  rudder  pedal  steering  is  augmented  by main   wheel   braking   action,   the   nose   wheel   can   be deflected  up  to  48  either  side  of  center.    Shock  loads which    would    normally    be    transmitted    to    the    rudder pedals   are   absorbed   by   a   spring   mechanism   in   the steering    linkage.        Retraction    of    the    landing    gear automatically   centers   the   nose   wheel   and   disengages the steering linkage from the rudder pedals. k. Wheel  Brake  System.    The  main  wheels are equipped with multiple-disc hydraulic brakes, actuated  by  master  cylinders  attached  to  the  toe  brake sections of the rudder pedals.  Brake fluid is supplied to the  system  from  a  reservoir  in  the  nose  compartment. Braking is permitted from either set of rudder pedals.  No emergency     brake     system     is     provided.          Repeated application    of    brakes    with    insufficient    cooling    time between    applications    will    cause    a    loss    of    braking efficiency,  and  may  cause  brake  failure,  wheel  failure, tire blowout, or destruction of wheel assembly by fire. 2-8.  PARKING BRAKE. Dual  parking  brake  valves  are  installed  below  the cockpit floor.  Both valves can be closed simultaneously by  pressing  both  brake  pedals  in  either  cockpit  position to    build    up    pressure,    then    pulling    out    the    handle, placarded 2-22