2.  Pull  the  filter  down  and  out  of  the retaining   springs   on   the   evaporator coil. 3. Fold  the  new  filter  to  insert  it  through the  access  doors.  The  filter;  must  be carefully  inserted  between  the  coil assembly   and   the   refrigerant   plumbing under  the  retaining  springs. 4.   Install   the   access   doors. b.  Aft  Evaporator  Filter  Replacement. 1. Remove   the   carpet   and   floor   panel behind   the   rear   spar,   and   remove   the cover  of  the  evaporator  plenum. 2. Remove  the  old  filter  from  behind  the retaining   springs   on   the   evaporator coil. 3.   Insert   the   new   filter   between   the retainer   springs   and   the   evaporator coil. 4.   Install   the   plenum   cover,   floor   panel, and   carpet. c.   Anti-icing,   Deicing   and   Defrosting   Protec- tion.  The  aircraft  is  protected  in  subfreezing  weather by  spraying  the  surfaces  (to  be  covered  with  protec- tive  covers)  with  defrosting  fluid.  Spraying  defrost- ing  fluid  on  aircraft  surfaces  before  installing  protec- tive   covers   will   permit   protective   covers   to   be removed  with  a  minimum  of  sticking.  To  prevent freezing  rain  and  snow  from  blowing  under  protec- tive  covers  and  diluting  the  fluid,  insure  that  protec- tive  covers  are  fitted  tightly.  As  a  deicing  measure, keep  exposed  aircraft  surface  wet  with  fluid  for  pro- tection  against  frost. TM  55-1510-221-10 NOTE Do  not  apply  anti-icing,  deicing  and defrosting  fluid  to  exposed  aircraft  sur- faces  if  snow  is  expected.  Melting  snow will  dilute  the  defrosting  fluid  and  form  a slush   mixture   which   will   freeze   in   place and  become  difficult  to  remove. 2-100.  ANTI-ICING,  DEICING  AND  DEFROSTING TREATMENT. Use  undiluted  anti-icing,  deicing,  and  defrosting fluid  (MIL-A-8243)  to  treat  aircraft  surfaces  for  pro- tection  against  freezing  rain  and  frost.  Spray  aircraft surface  sufficiently  to  wet  area,  but  without  exces- sive  drainage.  A  fine  spray  is  recommended  to  pre- vent  waste.  Use  diluted,  hot  fluid  to  remove  ice accumulations. 1. Remove  frost  or  ice  accumulations  from  air- craft  surfaces  by  spraying  with  diluted  anti- icing,  deicing,  and  defrosting  fluid  mixed  in accordance  with  table  2-12. 2.   Spray   diluted,   hot   fluid   in   a   solid   stream (not  over  15  gallons  per  minute).  Thor- oughly   saturate   aircraft   surface   and   remove loose   ice.   Keep   a   sufficient   quantity   of diluted,  hot  fluid  on  aircraft  surface  coated with  ice  to  prevent  liquid  layer  from  freez- ing.  Diluted,  hot  fluid  should  be  sprayed  at a  high  pressure,  but  not  exceeding  300  PSI. 3. When  facilities  for  heating  are  not  available and  it  is  deemed  necessary  to  remove  ice accumulations   from   aircraft   surfaces,   undi- luted  defrosting  fluid  may  be  used.  Spray undiluted   defrosting   fluid   at   15   minute Table  2- 12.   Recommended  Fluid  Dilution   Chart AMBIENT PERCENT PERCENT   WATER FREEZING   POINT TEMPERATURE DEFROSTING BY OF  MIXTURE  (“F) (ºF) FLUID  BY  VOLUME VOLUME (APPROXIMATE) 30º  and   above 20 80 10º 20º 30 70 0º 10º 40 60 -15º 0º 45 55 -25º -10º 50 50 -35º -20º 55 45 -45º -30º 60 40 -55º NOTES: 1.  Use  anti-icing  and  deicing  fluid  (MIL-A-8243)  or  commercial  fluids. 2.  Heat  Mixture  to  a  temperature  of  82º  to  93°C  (180º  to  200°F). 2-83