TM 1-1510-218-10 2-19 e.   Landing  Gear  Warning  System  D2  .    The landing  gear  warning  system  is  provided  to  warn  the pilot   that   the   landing   gear   is   not   down   and   locked during specific flight regimes.  Various warning modes result,  depending  upon  the  position  of  the  flaps.   With the  flaps  in  the  UP  or   APPROACH  position,  refer  to Figure  2-9,  Sheet  1,  and  either  or  both  power  levers retarded   below   approximately   79%   N₁,   the  warning horn   will   sound   intermittently   and   the   landing   gear switch  handle  lights  will  illuminate.    The  horn  can  be silenced by pressing the  WARNING  HORN  SILENCE switch adjacent to the landing gear switch handle; the light   in   the   landing   gear   switch   handle   cannot   be canceled.    The  landing  gear  warning  system  will  be rearmed if the power lever(s) are advanced.  Retarding the second power lever below 79% N₁ will activate the landing gear horn even though the silence system has been activated. To   prevent   the   warning   horn   sounding   during long    descents    or    an    ILS    approach,    a    pressure differential  "Q"  switch  is  connected  into  the  copilot's static line.  This switch prevents the warning horn from sounding until airspeed drops below 140 KIAS. With the flaps beyond the  APPROACH position, the warning horn and landing gear switch handle lights will  be  activated  regardless  of  the  power  setting.   The horn cannot be silenced in this case. T The landing gear warning system is provided to warn the pilot that the landing gear is not down and locked during specific flight regimes.   Various warning modes result depending upon the position of the flaps. At airspeeds above 140 KIAS with flaps in up or APPROACH  position  and  either  or  both  power  levers retarded   below   approximately   79%   N₁,  the  warning horn, located in the overhead control panel, will sound and    the    landing    gear    switch    handle    lights    will illuminate.   The horn is automatically silenced by a "Q" switch; however, the gear switch handle lights cannot be  extinguished.   The pressure differential "Q" switch is connected into the static line.   This switch prevents the warning horn from sounding steadily until airspeed drops below 140 KIAS. At airspeeds below 140 KIAS with flaps in the up or   APPROACH   position   with   either   or   both  power levers    retarded    below    approximately    79%   N₁   the warning  horn  will  sound  and  the  landing  gear  switch handle lights will illuminate.   The horn can be silenced by actuating the   WARNING  HORN  SILENCE switch, located  adjacent  to  the  landing  gear  switch  handle to the  up  position.    However,  the  lights  in  the  landing gear  switch  handle  cannot  be  canceled.     The  gear warning  silence  switch  is  a  magnetically  held  switch.   Once actuated, it will stay in the up position until both power   levers   are   advanced   above   81%   N₁   and/or airspeed increases above 140 KIAS. In either case (speeds above or below 140 KIAS),  the  landing  gear  warning  system  will  be rearmed if both power levers are advanced above 81% N₁. With the flaps beyond the  APPROACH position, the warning horn and landing gear switch handle lights 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  and  the   WARNING HORN SILENCE switch is actuated to the up position. f.    Landing  Gear  Warning  Horn  Test  Switch.   The warning horn and gear handle lights can be tested by placing the switch, placarded STALL WARN TEST / OFF / LDG GEAR WARN TEST, to the  LDG GEAR WARN  TEST   position.     The   gear  handle  lights  will illuminate and warning horn will sound.  Releasing the LDG  GEAR  WARN  TEST  switch to the  OFF position will  extinguish  the  gear  handle  lights  and  silence  the warning horn.   The landing gear warning horn circuit is protected    by   5 -ampere    circuit    breaker,    placarded LANDING   GEAR   WARN,   located   on   the   overhead circuit breaker panel. 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   strut   is   compressed.      This   switch   also activates   a   down-lock  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.   If the over-ride is used,    the    landing    gear    warning    horn    will    sound intermittently    and    two    red,    parallel-wired    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.      An extension lever, placarded LANDING GEAR ALTERNATE   EXTENSION,   is   located   on   the   floor between the crew seats.   The pump is located under