TM 1-1500-204-23-5 force  of  the  blades.    In  this  case,  the  plug  B  is  removed and installed in passage C of the governor.  This permits governor  oil  pressure  to  be  directed  to  the  rear  of  the cylinder, to decrease pitch.  Oil pressure is directed to the forward side of the cylinder to increase pitch.  See figure 2-10. b.   Installation.    The  following  general  procedures are for governor installation: (1)  Remove  all  portions  of  old  gasket  from mount base. (2) Remove nicks and burrs on governor base and mounting pad with a fine stone, Federal Specification SS-S-736, prior to installation. (3) Install a new gasket every time a governor is installed. (4)   Torque   mount   nuts   in   accordance   with applicable aircraft maintenance manual. (5)   Retorque   mount   nuts   after   the   first   15 minutes engine runup. c.   Rigging.    The  following  general  procedures  are for rigging the propeller governor.  Refer to the applicable maintenance manual for specific instructions. NOTE Engine   operation   shall   be   performed   by authorized personnel only. (1) Start engine. (2) Perform engine run-up check With PROP lever  in  the  full  forward  position,  adjust  power  lever  until propeller rpm stabilizes at high rpm. (3)  Next,  retard  PROP  lever  to  the  minimum rpm position. NOTE Adjust governor when rpm settings are not met as specified by the applicable maintenance manual. d.  Operation Checks.  At the time of propeller governor,  or  engine  installation,  the  following steps   are   normally   taken   to   ensure   that   the power plant will obtain takeoff rpm: (1) During ground runup, move the throttle to takeoff  position  and  note  the  resultant  rpm  and  manifold pressure. (2)  If the rpm obtained is higher or lower than the   takeoff   rpm   prescribed   in   the   instructions   of   the manufacturer,   reset   the   adjustable   stop,   as   shown   in figure  2-11,  on  the  governor  until  the  prescribed  rpm  is obtained. 2-15.      Propeller   Icing.      Ice   formation   on   a   propeller blade,  in  effect  produces  a  distorted  blade  airfoil  section which causes a loss in propeller efficiency.  Generally, ice collects    unsymmetrically    on    a    propeller    blade    and produces  propeller  unbalance  and  destructive  vibration. Icing  types,  anti-icing,  and  deicing  are  explained  in  the following paragraphs. a.    Icing  Types.    The  types  of  icing  are  glaze  or clear, rime, and glime or mixed.  Each type is described in the following paragraphs. (1)  Glaze  ice.    Glaze  (or  clear)  ice  is  hard, glossy,  and  heavy.    This  type  of  ice  forms  when,  after initial impact, the remaining liquid portion of the raindrop flows out over the surface freezing as a smooth sheet of solid ice. (2) Rime ice.  Rime ice has an irregular shape and  rough  surface.    It  is  brittle  and  frost-like  and  lighter than glaze ice.  Rime ice forms when raindrops are small. The  liquid  portion  remaining  after  initial  impact  freezes rapidly  before  the  drop  has  time  to  spread.    The  small frozen  droplets  trap  air  between  them  giving  the  ice  a white, frosty appearance. (3)   Glime   ice.      Glime   (or   mixed)   ice   is   a mixture of glaze and rime ice.  Glime ice is a hard, rough mixture  which  can  form  rapidly.    Glime  ice  forms  when raindrops vary in size or when liquid drops are mixed with snow or ice particles. b.       Anti-lcing.      Propeller   anti-icing   is   normally accomplished by spraying anti-icing fluid over the leading edge of the propeller.  The fluid is pumped from the fluid tank   through   small   tubes   that   open   just   outside   the propeller  hub  as  shown  in  figure  2-12.    The  centrifugal force  of  the  spinning  propeller  spreads  the  fluid  over  the leading edge of the blades. Change 2     2-17