TM 1-1510-223-10 with defrosting fluid.  Spraying defrosting fluid on aircraft surfaces   before   installing   protective   covers   will   permit protective   covers   to   be   removed   with   a   minimum   of sticking.  To prevent freezing rain and snow from blowing under protective covers and diluting the fluid, ensure that protective covers are fitted tightly.  As a deicing measure, keep exposed aircraft surface wet with fluid for protection against frost. Use undiluted anti-icing, deicing, and defrosting fluid (MILA-8243)    to    treat    aircraft    surfaces    for    protection against   freezing   rain   and   frost   Spray   aircraft   surface sufficiently to wet area, but without excessive drainage.  A fine spray is recommended to prevent waste.  Use diluted, hot fluid to remove ice accumulations. a. Remove  frost  or  ice  accumulations  from  aircraft surfaces  by  spraying  with  diluted  anti-icing,  deicing,  and defrosting fluid mixed in accordance with Table 2-12. b. Spray diluted, hot fluid in a solid stream (not over 15   gallons   per   minute).      Thoroughly   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   freezing.      Diluted,   hot   fluid should be sprayed at a high pressure, but not exceeding 300 PSL c.   When facilities for heating are not available and it is  deemed  necessary  to  remove  ice  accumulations  from aircraft  surfaces,  undiluted  defrosting  fluid  may  be  used. Spray  undiluted  defrosting  fluid  at  15  minute  intervals  to assure complete coverage Removal of ice accumulations using undiluted defrosting fluid is expensive and slow. d.   If    tires    are    frozen    to    ground,    use    undiluted defrosting  fluid  to  melt  ice  around  tire.    Move  aircraft  as soon as tires are free. 2-101.  APPLICATION OF EXTERNAL POWER. Before   connecting   the   power   cables   from   the external  power  source  to  the  aircraft,  ensure  that the  GPU  is  not  touching  the  aircraft  at  any  point Due  to  the  voltage  drop  in  the  cables,  the  two ground   systems   will   be   of   different   potentials. Should  they  come  in  contact  while  the  GPU  is operating,    arcing    could    occur.        Turn    off    all external  power  while  connecting  the  power  cable to, or removing it from, the external power supply receptacle.  Be certain that polarity of the external power  source  is  the  same  as  that  of  the  aircraft before it is connected. Minimum GPU requirements  are  as  follows:  400-amperes,  28V continuous  output  DC  and  115V,  3  phase,  400 cycle, 3 KVA continuous output AC. An external power source is often needed to supply. The  electric  current  required  to  properly  ground  service the  aircraft  electrical  equipment  and  to  facilitate  starting the aircraft's engines.  An external DC power receptacle is installed on the underside of the right wing, just outboard of the engine nacelle.  An external AC power receptacle is installed on the underside of the left wing, just outboard of the engine nacelle. 2-102. SERVICING OXYGEN SYSTEM. The  oxygen  system  furnishes  breathing  oxygen  to the   pilot,   copilot,   and   first   aid   position.      The   oxygen cylinder location is shown in figure 2-24. a. Oxygen System Safety Precautions. Keep fire and heat away from oxygen equipment Do not smoke while working with or near oxygen equipment, and take care not to generate sparks with  carelessly  handled  tools  when  working  on the oxygen system. (1)   Keep   oxygen   regulators,   cylinders,   gages, valves,  fittings,  masks,  and  all  other  components  of  the oxygen system free of oil, grease, gasoline, and all other readily combustible substances.  The utmost care shall be exercised    in    servicing,    handling,    and    inspecting    the oxygen system. (2)   Do  not  allow  foreign  matter  to  enter  oxygen lines. (3)   Never allow electrical equipment to come into contact with the oxygen cylinder. (4)   Never use oxygen from a cylinder without first reducing its pressure through a regulator. b. Replenishing Oxygen System. 1. Remove oxygen access door on outside of aircraft (fig.  2-24). 2. Remove protective cap on oxygen system filler valve. 3. Attach oxygen hose from oxygen servicing unit to filler valve. If the oxygen system pressure is below 200 PSI, do not attempt to service system Make an entry on DA Form 240813 . 2-90