TM 1-151022310 2-65.  CHEMICAL TOILET. a. Description.       A    side-facing    chemical    toilet    is installed in the aft cabin area, and can also be used as an additional    seat    Two    hinged-lid    half-sections    must    be raised to gain access to the toilet Waste is stored within a removable container located below the seat in the cabinet assembly.  This non-flushing system uses a dry chemical preparation to deodorize the stored waste.  A toilet tissue dispenser is contained in a slide-out compartment on the forward   side   of   the   toilet   cabinet   A   box   of   disposable waste  container  liners  and  a  box  of  chemical  deodorant packets are alsostored in the cabinet b. Operation.   During  use,  a  removable  throw-away plastic liner is attached to the waste container.  After use, dry chemical deodorant obtained from the storage cabinet is deposited on the waste and the hinged lid sections are closed   over   the   cavity.      After   each   flight,   the   waste container    must    be    removed,    emptied,    relined,    and replaced in the cabinet Consumable toilet items should be resupplied as needed. 2-66.  SUN VISORS. When adjusting the sun visors, grasp only by the top metal attachment to avoid damage to the plastic shield. Individual  sun  visors  are  provided  for  the  pilot  and copilot   (fig.      2-8).      Each   visor   is   manually   adjustable. When  not  needed  as  a  sun  shield,  each  visor  may  be manually  rotated  to  a  position  flush  with  the  top  of  the cockpit so that it does not obstruct view through the windows. 2-67.  RELIEF TUBE. One relief tube is provided, located immediately aft of the cargo door on the left side of the fuselage. Section VIII.  HEATING, VENTILATION, COOLING, AND ENVIRONMENTAL CONTROL SYSTEM 2-68.  HEATING SYSTEM. Warm  air  for  heating  the  cockpit,  mission  equipment compartment,  and  windshield  defrosting  is  provided  by bleed    air    from    both    engines.        Engine    bleed    air    is combined with ambient air in the heating and pressurization flow control unit in each engine nacelle.  If the mixed bleed air is too warm for cockpit comfort, it is cooled    by    being    routed    through    an    air-to-air    heat exchanger located in the forward portion of each inboard wing.  If the mixed bleed air is not too warm, the air-to-air heat  exchangers  are  bypassed.    The  mixed  bleed  air  is then  ducted  to  a  mixing  plenum,  where  it  is  mixed  with cabin recirculated air.  The warm air is then ducted to the cockpit  outlets,  windshield  defroster  outlets,  and  to  the floor outlets in the mission equipment compartment.  The environmental system is shown in figure 2-26. a. Bleed air flow control unit.  A bleed air flow control unit, located forward of the firewall in each engine nacelle controls the flow of bleed air and the mixing of ambient air to   make   up   the   total   airflow   to   the   cabin   for   heating, windshield defrosting, pressurization, and ventilation.  The unit  is  electronically  controlled  with  an  integral  electric solenoid firewall shutoff valve, controlled by the bleed air switches located on the overhead control panel (fig.  2-13) and a normally open solenoid valve operated by the right landing gear safety switch b. Pneumatic  bleed  air  shutoff  valve.    A  pneumatic shutoff valve is provided in each engine nacelle to control the  flow  of  bleed  air  to  the  surface,  antenna,  and  brake deice systems.  These valves are controlled by the bleed air valve switches located on the overhead control panel (fig.  2-13). c. Bleed   air   valve   switches.      The   bleed   air   flow control unit shutoff valve and pneumatic bleed air shutoff valves  are  controlled  by  two  LEFT  and  RIGHI  switches placarded ENVIRO & PNEU BLEED AIR - PNEU ONLY - ON,  located  on  the  overhead  control  panel  (fig.    2-13). When set to the ON position, both the environmental flow control unit shutoff valve and the pneumatic shutoff valve are   open;   when   set   to   the   PNEU   ONLY   position,   the environmental  flow  control  unit  shutoff  valve  is  closed, and the pneumatic bleed air valve is open; in the ENVIRO & PNEU position, both are closed.  For maximum cooling on  the  ground,  turn  the  bleed  air  valve  switches  to  the PNEU ONLY position d. Cabin   temperature   mode   selector   switch.      A switch  placarded  CABIN  AIR  MODE  SELECT  -  OFF  - AUTO-  AC  COLD  OPN  10C  to  -25C  -  MAN  COOL  - MAN    HEAT    located    on    the    overhead    control    panel, controls    cockpit    and    mission    avionics    compartment heating and air conditioning.  When the cabin temperature mode  selector  switch  is  set  to  the  AUTO  position,  the heating and 2-58