TM 1-1500-204-23-1 (b) Ice  deposit  prevention.    Deicing  fluid will protect aircraft surfaces as long as it remains on the surfaces.      However,   freezing   rain   will   tend   to   wash surfaces  clean  of  fluid,  as  well  as  dilute  the  fluid  to  the point  at  which  ice  will  form.    The  amount  of  protection afforded  by  the  fluid  depends  on  the  amount  of  freezing rain.  The following steps should be taken if ice caused by freezing rain is expected. 1 On  aircraft  for  which  covers  are available,  a  coating  of  fluid  applied  before  covers  are installed   will   prevent   covers   from   freezing   on   aircraft surfaces   and   make   removal   of   covers   much   easier. However,   care   should   be   taken   to   ensure   that   only   a minimum amount of rain is allowed to blow under covers Otherwise, dilution of fluid will allow freezing to occur 2 On larger aircraft for which covers are unavailable, the best method of prevention is to keep the surfaces wet with fluid.  As long as this fluid remains on the surface, protection is afforded.  Since rain eventually will dilute the fluid and render it ineffective for preventing  ice  formation,  protection  must  be  maintained during   precipitation   by   continual   spraying   of   fluid.      If weather   conditions   are   such   that   It   is   impossible   to prevent ice formation, removal should be accomplished (c) Frost deposit prevention. A satisfactory procedure for protection of aircraft from frost is  the  application  of  a  layer  of  unheated,  undiluted,  de- icing fluid to aircraft surfaces after the last flight of the day or  as  close  to  midnight  as  possible,  whichever  is  later. This should permit early morning departure without further fluid application.  The length of time that an aircraft will be protected by a single coat of fluid depends on the climatic conditions. (2) Removal    of    deposits.          The     following paragraphs  explain  the  removal  of  snow,  ice,  and  frost deposits. CAUTION Extreme    care    shall    be    taken    to prevent   damage   to   aircraft.      Sharp instruments,  such  as  picks,  knives, or  screwdrivers,  will  not  be  used  to loosen ice formation (a) Snow  removal.    Deicing  fluids  should  not be   used   to   remove   heavy   snow   accumulation.      Snow absorbs wasteful amounts of fluid to form a slush which is difficult to remove and eventually will refreeze.  The slush will  get  into  control  surface  hinges  and  freeze,  causing additional difficulty.  Snow will be removed by brushing or sweeping  or  by  moving  the  covers.    Usually  after  snow removal, a layer of rough ice remains.  This frozen crust can  be  removed  with  hot,  diluted,  deicing  fluid.    In  an emergency  when  aircraft  must  get  off  ground  as  quickly as possible, thin layers of snow can be removed with hot, diluted,   deicing   fluid.      If   sufficient   fluid   is   used,   the combination of heat from fluid and force of the stream will permit    removal    of    slush,    as    it    Is    formed    without refreezing.    Quantity  of  heated  fluid  required  for  snow removal Is prohibitive.  Remove snow, water and Ice from aircraft fuel filler cap wells before removing fuel filler cap. Only  one  filler  cap  should  be  removed  at  a  time,  and  it should     be     replaced     immediately     after     servicing     is completed. (b) Ice and frost removal.  If hangars and  covers  cannot  be  used  to  prevent  frozen  formations on    aircraft,    but    equipment    is    available    for    heating fluidwater solutions, removal of frozen formations by hot, diluted,  deicing  fluid  will  be  used  in  place  of  preventive spraying.    Accumulations  should  be  allowed  to  form  and then   be   removed   just   after   each   precipitation   or   just before   each   flight,   whichever   is   most   practicable   or compatible with operational mission of the aircraft f. Preventive Maintenance.  Accomplish the following preventive maintenance procedures (1) Avoid    parking    aircraft    in    wet    or    slushy areas. (2) Use caution when towing aircraft In extremely    low    temperatures    to    prevent    damage    to hydraulic seals which would result In strut leakage. (3) Inspect  oil  and  fuel  drains  and  crankcase breathers  for  ice  and  frost  Remove  any  existing  frost  or ice. (4) If   layovers   are   to   be   over   4   hours   and temperature is below -20°F (-290°C), remove battery and store in a warm place. (5) Drain oil system when there is no provision available  for  preheating  oil  and  a  long  layover  period  is anticipated. (6) When    temperature    rises    above    freezing during  a  long  layover,  drain  fuel  and  oil  tank  sumps  of water before temperature drops. (7) Install    protective    covers    and    shields    to protect aircraft from accumulation of snow, frost, or ice. 10-5