TM 1-1510-224-10 PARKING   BRAKE   on   the   pilot's   subpanel   (fig.   2-8). 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. 2-9.  ENTRANCE AND EXIT PROVISIONS. NOTE Two  keys  are  provided  in  the  loose tools  and  equipment  bag.    Both  keys 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  cabin  door  (fig.  2-11),  hinged  at  the bottom,  provides  a  stairway  for  normal  and  emergency entrance   and   exit.      In   the   closed   position,   the   door becomes  an  integral  part  of  the  cargo  door.    The  cabin door is provided with steps, two of which 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.    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/l   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 cargo door (fig. 2-11), 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  pressure  vessel while  in  flight.    The  door  locking  mechanism  is  operated only   from   inside   the   aircraft,   and   is   operated   by   two handles,  one  in  the  bottom  forward  portion  of  the  door and the other in the upper aft portion of the door.  When the upper aft handle is operated per placard instructions, cam-type  latches  (two  on  the  forward  side  of  the  door and two on the aft side) rotate, capturing posts mounted on  the  fuselage  side  of  the  door  opening.    The  bottom handle, when operated per placard instructions, actuates four  pin-lug  latches  across  the  bottom  of  the  door.    A button  on  the  upper  aft  handle  must  be  pressed  before the handle can be released to open or latch the door.  A latching  lever  on  the  bottom  handle  must  be  lifted  to release   the   handle   before   the   lower   latches   can   be opened.      These   act   as   additional   aids   in   preventing accidental opening or unlatching of the door.  The cabin and  cargo  doors  are  equipped  with  dual  sensing  circuits to provide the crew with remote indication of cabin/cargo door    security.        An    annunciator,    placarded     CABIN DOOR,  will  illuminate  if  the  cabin  or  cargo  door  is  open and the BATTERY switch is on.  If the  BATTERY switch is  off,  the  annunciator  will  illuminate  only  if  the  cabin door     is     not     securely     closed     and     latched.          The cabin/cargo door sensing circuit receives power from the hot battery bus. CAUTION When     operating     the     cargo     door, ensure  that  the  cabin  door  is  closed and    locked.        Operating    the    cargo door   while   the   cabin   door   is   open may    damage    the    door    hinge    and adjacent structure. (1)  Opening the cargo door. CAUTION To prevent damage to the mechanism, avoid side loading of the gas springs. 1. Handle  access  door  (lower  forward corner of door) - Unfasten and open. 2. Handle   -   Lift   hook   and   move   to OPEN position. 2-24