TM 55-1510-221-10 Operation  of  the  surface  deice  system  in ambient   temperatures   below   -40°C   can cause   permanent   damage   to   the   deice boots. b.   Operation. (1.)  Deice   boots   are   intended   to   remove ice  after  it  has  formed  rather  than  prevent  its  forma- tion.  For  the  most  effective  deicing  operation,  allow at  least  l/2  inch  of  ice  to  form  on  the  boots  before attempting  ice  removal.  Very  thin  ice  may  crack  and cling  to  the  boots  instead  of  shedding. NOTE Never  cycle  the  system  rapidly,  this  may cause  the  ice  to  accumulate  outside  the contour  of  the  inflated  boots  and  prevent ice  removal. (2.)  A  three  position  switch  on  the  over- head   control   panel   placarded   SURF   DEICE   MAN- UAL  -  OFF  -  SINGLE  CYCLE  AUTO,  controls  the deicing  operation.  The  switch  is  spring  loaded  to return   to   the   OFF   position   from   SINGLE   CYCLE AUTO   or   MANUAL.   When   the   SINGLE   CYCLE AUTO   position   is   selected,   the   distributor   valve opens  to  inflate  the  wing  boots.  After  an  inflation period   of   approximately   6   seconds,   an   electronic timer  switches  the  distributor  to  deflate  the  wing boots  and  a  4  second  inflation  begins  in  the  horizon- tal  stabilizer  boots.  When  these  boots  have  inflated and  deflated,  the  cycle  is  complete. (3.) If  the  switch  is  held  in  the  MANUAL position,   the   boots   will   inflate   simultaneously   and remain   inflated   until   the   switch   is   released.   The switch   will   return   to   the   OFF   position   when released.  After  the  cycle,  the  boots  will  remain  in  the vacuum  hold  down  condition  until  again  actuated by  the  switch. (4.) Either  engine  is  capable  of  providing sufficient  bleed  air  for  all  requirements  of  the  sur- face  deicer  system.  Check  valves  in  the  bleed  air  and vacuum   lines   prevent   backflow   through   the   system during  single-engine  operation.  Regulated  pressure  is indicated  on  a  gage,  placarded  PNEUMATIC  PRES- SURE,  located  on  the  copilots  subpanel. 2-52.  ANTENNA  DEICING  SYSTEM. a. Description.   The  antenna  deice  system removes   ice   accumulation   from   the   dipole   mission 2-42 antennas.  The  system  consists  of  two  ejector  distrib- utor  valves,  a  regulator,  manifold,  and  flexible  tub- ing.   Control   is   accomplished   through   a   timing   cir- cuit   and   an   antenna   deice   switch   located   on   the overhead  control  panel  (fig.  2-12).  Erosion  resistant tape  is  applied  to  the  surface  of  mission  blade  anten- nas  not  having  deice  boots. b. Antenna  Deice  System  Switch.  The  antenna deice   system   is   controlled   by   a   switch   placarded ANT  DEICE,  SINGLE  -  OFF  -  MANUAL  located on  the  overhead  control  panel  (fig.  2-12).  The  switch is  spring  loaded  to  return  to  the  OFF  position  from the  SINGLE  or  MANUAL  position.  When  the switch  is  set  to  the  single  position,  the  system  will run  through  one  timed  inflation-deflation  cycle. When  the  switch  is  held  in  the  MANUAL  position the  boots  will  inflate  and  remain  inflated  until  the switch  is  released. c.  Forward   Wide   Band   Data   Link   Antenna Radome  Anti-Ice.  The  forward  wide  band  data  link antenna  radome  anti-ice  system  utilizes  engine  bleed air  to  prevent  the  formation  of  ice  on  the  radome. The  system  is  controlled  by  a  switch  placarded RADOME  located  on  the  overhead  control  panel. The   circuit   is   protected   by   a   circuit   breaker   plac- arded   RADOME,   located   on   the   overhead   circuit breaker  panel  (fig.  2-26). d.  Operation. (1.)  Deice   boots   are   intended   to   remove ice  after  it  has  formed  rather  than  prevent  its  forma- tion.  For  the  most  effective  deicing  operation,  allow at  least  l/8  to  l/4  inch  of  ice  to  form  on  the  boots before  attempting  ice  removal.  Very  thin  ice  may crack  and  cling  to  the  boots  instead  of  shedding. NOTE Never  cycle  the  system  rapidly,  this  may cause  the  ice  to  accumulate  outside  the contour  of  the  inflated  boots  and  prevent ice  removal. 2-53.   PROPELLER   ELECTROTHERMAL   ANTI-ICE SYSTEM. a. Description.   Electrothermal   anti-ice   boots are  cemented  to  each  propeller  blade  to  prevent  ice formation  or  to  remove  the  ice  from  the  propellers. Each  thermal  boot  consists  of  one  outboard  and  one inboard  heating  element,  and  receives  electrical power  from  the  deice  timer.  This  timer  sends  cur- rent  to  all  propeller  deice  boots  and  prevents  the boots  from  overheating  by  limiting  the  time  each element   is   energized.   Four   intervals   of   approxi- mately  30  seconds  each  complete  one  cycle.  Current