TM 55-1510-222-10 KIAS) the landing gear warning system will be rearmed if both power levers are advanced above 86% N₁. With  the  flaps  beyond  the  APPROACH  position, the    warning    horn    and    landing    gear    switch    handle annunciators  will  be  activated  regardless  of  the  power setting.  The horn cannot be silenced in this case, until either   the   landing   gear   is   lowered,   or   the   flaps   are retracted to the UP or APPROACH position. f. Landing   Gear   Warning   Horn   Test   Switch. The warning horn and gear handle annunciators can be tested  by  placing  the  switch  placarded  STALL  WARN TEST OFF LDG GEAR WARN TEST to the LDG GEAR WARN    TEST    position    (fig.    2-5).    The    gear    handle annunciators    will    illuminate,    and    warning    horn    will sound.  Releasing the LDG GEAR WARN TEST switch to   the   OFF   position   will   extinguish   the   gear   handle annunciators, and silence the warning horn.  The landing gear  warning  horn  circuit  is  protected  by  a  5-ampere circuit    breaker,    placarded    LANDING    GEAR    HORN, located in the overhead circuit breaker panel (fig. 2-6). 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  DOWN  LOCK  REL  located  adjacent to  the  landing  gear  handle  (fig.  2-5).    If  the  override  is used,    the    landing    gear    warning    horn    will    sound intermittently  and  two,  red,  parallel-wired  annunciators 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. An  extension  lever,  placarded  LANDING  GEAR ALTERNATE    EXTENSION,    is    located    on    the    floor between the crew seats.  A manual pumping action with the   handle   lowers   the   landing   gears.      The   hydraulic pump   utilized   to   manually   lower   the   gear   is   located under the floor. To  engage  the  system,  pull  the  LANDING  GEAR CONTROL   circuit   breaker,   located   in   the   overhead circuit breaker panel (fig. 2-6), 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 annunciators   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  gears,  ensure  the  extension lever  is  in  the  full  down  position  prior  to  stowing  the pump   handle   in   the   retaining   clip.      When   the   pump handle is stowed, an internal relief valve is actuated to relieve the hydraulic pressure in the pump. NOTE If for any reason the three green GEAR DOWN   indicators   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.  The extension lever should then be stowed. After   a   practice   alternate   extension,   stow   the extension handle, 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,  8  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. 2-13