TM 1-1510-223-10 a  4  second  inflation  begins  in  the  horizontal  stabilizer, stabilon,   and   taillet   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  surface deice   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 PRESSURE, located on the center subpanel. (5)   Under    conditions    where    one    bleed    air source  is  inoperative,  sufficient  bleed  air  pressure  for deice boot inflation may not be available.  Prior to deice boot  inflation,  check  the  regulated  bleed  air  pressure gage  for  a  minimum  of  16  PSL  If  insufficient  pressure exists,  increasing  engine  N1  and/or  decreasing  aircraft altitude will increase bleed air pressure. 2-52. ANTENNA DEICING SYSTEM. a. Description.        The    antenna    deicing    system removes  or  prevents  ice  accumulation  on  the  mission antennas.    Pressure    regulated    bleed    air    from    both engines supply pressure to inflate the boots.  To assure operation  of  the  system,  in  the  event  of  failure  of  one engine,  a  check  valve  is  incorporated  in  the  bleed  air line   from   each   engine   to   prevent   loss   of   pressure through    the    compressor    of    the    inoperative    engine. Inflation     and     deflation     phases     are     controlled     by distributor valves. To  ensure  adequate  bleed  air  pressure  to the    deice    boots,    do    not    simultaneously actuate surface and antenna deice systems in the manual mode. NOTE Under    conditions    where    one    bleed    air source   is   inoperative,   sufficient   bleed   air pressure for deice boot inflation may not be available.      Prior   to   deice   boot   inflation, check the regulated bleed air pressure gage for   a   minimum   of   16   PSI.      If   insufficient pressure exists, increasing engine N, and/or decreasing    aircraft    altitude    will    increase bleed air pressure. b. Antenna  Deice  System  Switch.     The   antenna deice    system    is    controlled    by    a    switch    placarded ANTENNA, MANUAL SINGLE CYCLE AUTO located on the  overhead  control  panel  (fig.    2-13).    The  switch  is spring   loaded   to   return   to   the   off   position   from   the SINGLE CYCLE AUTO or MANUAL position When the switch is set to the SINGLE CYCLE AUTO 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. Operation.  Deice boots are intended to remove ice after it has formed rather than prevent its formation. For  the  most  effective  deicing  operation,  allow  at  least 1/8   to   1/4   inch   of   ice   to   form   on   the   boots   before attempting 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. FORWARD INTEROPERABLE DATA LINK ANTENNA RADOME ANTI-ICE. The  forward  interoperable  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 ON, located on the overhead control panel (fig.  2-13).  The circuit is protected   by   a   7.5ampere   circuit   breaker   placarded RADOME   ANTI-ICE,   located   on   the   overhead   circuit breaker panel (fig.  2-7). 2-54. PROPELLER ELECTRIC DEICE SYSTEM. a. Description.  The propeller electric deice system includes  electrically  heated  deice  boots,  slip  rings  and brush block assemblies, a timer for automatic operation, ammeter, circuit breakers for left and right propeller and control  circuit  protection,  and  two  switches  located  on the overhead control panel (fig.  2-13), for automatic or manual control of the system. b. Automatic  Operation.    The  two  position  switch located on the overhead control panel, placarded PROP AUTO ON, is provided to activate the automatic system. Upon  placing  the  switch  to  the  ON  position,  the  timer diverts power through the brush block and slip ring to all heating  elements  on  one  propeller.    Subsequently,  the timer 2-49