TM 1-1510-218-10 2-25 2-10.  WHEEL BRAKE SYSTEM. The   main   landing   wheels   are   equipped   with multiple-disc    hydraulic    brakes    actuated    by    master cylinders  attached  to  the  rudder  pedals  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  wheel.    No  emergency brake  system  is  provided.    Repeated  and  excessive application  of  brakes,  without  allowing  sufficient time for  cooling  to  accumulate  between  applications,  will cause   loss   of   braking   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. 2-11.  PARKING BRAKE HANDLE. Dual parking brake valves are installed below the cockpit floor. Both valves can be closed simultaneously  by  pressing  both  brake  pedals  on  the pilot's  side  to  build  up  pressure  and  then  pulling  out the handle, placarded   PARKING  BRAKE,  on  the  left subpanel, Figures 2-6 and 2-8.  The parking brake can be set by both the pilot and the copilot on the   D  and   T models only.  Pulling the handle full out sets the check  valves  in  the  system  and  any  pressure  being applied   by   the   toe   brakes  is  maintained.    Parking brakes are released when the brake handle is pushed in.  Parking brakes shall not be set during flight. 2-12.  ENTRANCE AND EXIT PROVISIONS. CAUTION Structural  damage  may  be  caused  if  more than one person, or a maximum weight of 300  pounds,  is  on  the  entrance  door  at  a time. NOTE Two  keys  are  provided  in  the  loose  tools and  equipment  bag.   Both  keys  will  fit  the locks on the cabin door, emergency hatch, aft belly access door, and the right and left nose avionics doors.  These keys will fit all Army C -12 series aircraft. Avoid inadvertently   locking   the   cabin   entrance door prior to entering the aircraft. a.   Cabin Door  C  .  A swing-down door, hinged at the bottom, provides positive cabin security for flight and     a     convenient     stairway     for     entry     and     exit, Figure 2-11.  Two of the three steps are movable and automatically  fold  flat  against  the  door  in  the  closed position.  A plastic encased cable provides support for the    door    in    the    open    position,    a    handhold    for passengers,  and  a  convenience  for  closing  the  door from the inside.  A hydraulic damper permits the door to lower gradually during opening.  An inflatable rubber door  seal  around  the  door  expands  to  positively  seal the   pressure   vessel   while   the   aircraft   is   in   flight.   Engine  bleed  air  provides  the  pressure  to  inflate  the seal.  The door locking mechanism is operated by the handle   in   the   center   of   the   door.      The   inside   and outside    handles    are    mechanically    interconnected.   When  the  handle  is  rotated  per  placard  instructions, two  latches  hook  into  the  door  frame  at  the  top,  and two  lock  bolts  on  each  side  of  the  door  lock  into  the frame on the sides.  There are four sight openings on the  inner  facing  of  the  door;  one  opening  over  each locking bolt.  A green stripe painted on the locking bolt aligns  with  a  black  pointer  in  the  sight  opening  when the  door  is  in  a  locked  condition.    A   CABIN  DOOR annunciator   light   in   the   caution/advisory   panel   will illuminate  if  the  door  is  not  fully  locked.    The  cabin door  may  be  removed  for  flight  by  installing  Beech Aircraft   Corporation   Kit   100-4006.    Flights  with  the door  removed  must  be  in  accordance  with  the  FAA approved flight manual supplement, which accompanies this kit. (1)   A   button   adjacent   to   the   door   handle, both  inside  and  outside  the  cabin,  must  be  pressed before  the  handle  can  be  rotated  to  open  the  door.   This acts as an aid to preventing accidental opening. (2)   A   small   round   window   just   above   the second  step  permits  observation  of  the  pressurization safety lock bellows.  A placard adjacent to the window instructs  the  operator  to  make  certain  the  safety  lock arm  is  in  position  around  the  bellows  shaft.    Pushing the     red     button     switch     adjacent     to     the     window illuminates the mechanism inside the door.