TM 55-1510-222-10 j. Steerable   Nose   Wheel.        The    aircraft    is maneuvered on the ground by the steerable nose wheel system.  Direct linkage from the rudder pedals (fig. 2-7) 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  the  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  or  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 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   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   cockpit position.  Parking brake shall not be set during flight. 2-9. ENTRANCE AND EXIT PROVISIONS. NOTE Two   keys   are   provided   in   the   loose tools  and  equipment  bag.    Both  keys will  fit  the  locks  on  the  cabin  door, emergency hatch, tailcone access door    and    the    right    and    left    nose avionics compartment doors. a. Cabin Door. CAUTION Structural  damage  may  occur  if  more than   one   person   is   present   on   the airstair  cabin  door  at  one  time.    The door is weight limited to 300 pounds. An  airstair  door  (fig.  2-8),  hinged  at  the  bottom, provides a stairway for normal and emergency entrance and exit.  Two of the steps fold flat against the door in the closed position.  A step folds down over the door sill when  the  door  opens  to  provide  a  platform  (step)  for door seal protection.  A plastic encased cable provides a handhold  and  support  for  the  door  in  the  open  position and a convenience for closing the door from inside.  A hydraulic  damper  permits  the  door  to  lower  gradually during opening. A rubber seal around the door, seals the pressure  vessel  while  the  aircraft  is  in  flight.    The  door locking   mechanism   is   operated   by   either   of   the   two mechanically   interconnected   handles,   one   inside   and the   other   outside   the   door.      When   either   handle   is rotated, three rotating cam-type latches on either side of the door, capture posts mounted on the cargo door.  In the closed position, the door becomes an integral part of the  cargo  door.    A  button  adjacent  to  the  door  handle must be depressed before the handle can be rotated to open  the  door.    A  bellows  behind  the  button  is  inflated when  the  aircraft  is  pressurized  to  prevent  accidental unlatching   and/or   opening   of   the   door.      A   placard adjacent  to  the  window  instructs  the  operator  that  the safety  lock  arm  is  in  position  around  the  bellows  shaft which indicates a properly locked door.  Pushing the red button  adjacent  to  the  window  will  illuminate  the  inside door  mechanism.  A  CABIN  DOOR  annunciator  on  the caution/  advisory  panel  will  illuminate  if  the  door  is  not closed   and   all   latches   fully   locked.      The   cabin   door opening is 21.5 inches wide by 50.0 inches high. b. Cargo   Door.      A   swing-up   door   (fig.   2-8), hinged at the top, provides access for loading cargo or bulky  items.    The  cargo  door  opening  is  52.0  inches wide  by  52.0  inches  high.    After  initial  opening  force  is applied, gas springs will completely open the cargo door automatically.      The   door   is   counterbalanced   and   will remain in the open position.  A door support rod is used to   hold   the   door   in   the   open   position,   and   to   aid   in overcoming  the  pressure  of  the  gas  spring  assemblies when  closing  the  door.    Once  closed,  the  gas  springs apply  a  closing  force  to  assist  in  latching  the  door.    A rubber seal around the door seals the 2-15