TM 1-1510-225-10 2-25 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. g.  Landing   Gear   Alternate   Extension.      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. 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. To engage the system, pull the LANDING GEAR RELAY circuit breaker, located on the pilot's subpanel, and ensure that the  LDG  GEAR  CONTROL 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  RELAY circuit   breaker,   and   retract   the   gear   in   the   normal manner with the landing gear control handle. h.  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. i.    Nose Wheel Steering System.  The aircraft is   maneuvered   on   the   ground   by   the   nose   wheel steering system.  Direct linkage from the rudder pedals 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.   Refer  to Figure 2-7. CAUTION 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. j.    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. 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    PARKING   BRAKE,   on   the pilot's  subpanel.    Pulling  the  handle  full  out  sets  the check  valves  in  the  system  and  any  pressure  being applied  by  the  toe  brakes  is  maintained.   The  parking brake is released when the brake handle is pushed in.   The parking brake may be set from either the pilot's or copilot's  position.    The  parking  brake  shall  not  be  set during flight. WARNING