TM  55-1510-221-10 Continued   pumping   of   handle   after GEAR   DOWN   position   indicator   lights (3)   are   illuminated   could   damage   the drive  mechanism,  and  prevent  subsequent gear   retraction. h. Landing  Gear  Alternate  Extension  Handle. Manual   landing   gear   extension   is   provided   through a  manually  powered  system  as  a  backup  to  the  elec- trically   operated   system.   Before   manually   extending the  gear,  make  certain  that  the  landing  gear  switch is  in  the  down  position  with  the  LANDING  GEAR RELAY  circuit  breaker  pulled.  Pulling  up  on  the alternate  engage  handle,  located  on  the  floor,  and turning  it  clockwise  will  lock  it  in  that  position. When  the  alternate  engage  handle  is  pulled,  the motor   is   electrically   disconnected   from   the   system and  the  alternate  drive  system  is  locked  to  the  gear- box  and  motor.  When  the  alternate  drive  is  locked in,  the  chain  is  driven  by  a  continuous  action  ratchet which  is  activated  by  pumping  the  landing  gear alternate   extension   handle   adjacent   to   the   alternate engage  handle. k. Wheel  Brake  System.  The  main  wheels  are equipped   with   multiple-disc   hydraulic   brakes   actu- ated  by  master  cylinders  attached  to  the  rudder  ped- als  at  the  pilot’s  and  copilot’s  position.  Braking  is permitted  from  either  set  of  rudder  pedals.  Brake fluid  is  supplied  to  the  system  from  the  reservoir  in the  nose  compartment.  The  toe  brake  sections  of  the rudder  pedals  are  connected  to  the  master  cylinders which  actuate  the  system  for  the  corresponding wheels.   No   emergency   brake   system   is   provided. Repeated  and  excessive  application  of  brakes,  with- out  allowing  sufficient  time  for  cooling  to  accumu- late  between  applications,  will  cause  a  loss  of  brak- ing  efficiency,  possible  failure  of  brake  or  wheel structure,  possible  blowout  of  tires,  and  in  extreme cases  may  cause  the  wheel  and  brake  assembly  to  be destroyed  by  fire. (1.) After  a  manual  landing  gear  extension has  been  made,  do  not  stow  the  handle,  move  any landing  gear  controls,  or  reset  any  switches  or  circuit breakers.  The  gear  cannot  be  retracted  manually. 2-8. PARKING BRAKE. (2.) After  a  practice  manual  extension,  the alternate  handle  may  be  stowed  and  the  landing  gear retracted   electrically.   Rotate   the   alternate   engage handle  counterclockwise  and  push  it  down.  Stow  the handle,  push  in  the  LANDING  GEAR  RELAY  cir- cuit   breaker   on   the   overhead   circuit   breaker   panel and  retract  the  gear  in  the  normal  manner  with  the landing   gear   switch.   Refer   to   Chapter   9   for   emer- gency  gear  extension  procedures. Dual   parking   brake   valves   are   installed   below the  cockpit  floor.  Both  valves  can  be  closed  simulta- neously  by  pressing  both  brake  pedals  to  build  up pressure,    then   pulling   out   the   handle   placarded PARKING  BRAKE,  on  the  left  subpanel.  Pulling the  handle  full  out  sets  the  check  valves  in  the  sys- tem  and  any  pressure  being  applied  by  the  toe brakes  is  maintained.  Parking  brakes  are  released when  the  brake  handle  is  pushed  in.  The  parking brake  may  be  set  from  either  cockpit  position.  Park- ing  brakes  shall  not  be  set  during  flight. i. Tires.  The  aircraft  is  equipped  with  dual  22 x  6.75  -  10  tubeless,  8-ply  rated,  rim-inflation  tires on  each  main  gear.  The  nose  gear  is  equipped  with a  single  22  x  6.75  -   10,  8-ply  rated,  tubeless,  rim- inflated   tire. 2-9.  ENTRANCE  AND  EXIT  PROVISIONS. NOTE j. Steerable  Nose  Wheel.  The  aircraft  can  be Two  keys  are  provided  in  the  loose  tools maneuvered  on  the  ground  by  the  steerable  nose and  equipment  bag.  Both  keys  will  fit  the wheel  system.  Direct  linkage  from  the  rudder  pedals locks  on  the  cabin  door,  emergency  hatch, (fig.  2-8)  to  the  nose  wheel  steering  linkage  allows tailcone  access  door  and  the  right  and  left the  nose  wheel  to  be  turned  12°  to  the  left  of  center nose   avionics   compartment   doors. or  14°  to  the  right.  When  rudder  pedal  steering  is augmented  by  the  main  wheel  braking  action,  the nose  wheel  can  be  deflected  up  to  48°  either  side  of center.  Shock  loads  which  would  normally  be  trans- mitted  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. 2-14