TM 1-1500-204-23-1 CHAPTER 10 ARCTIC, DESERT, AND TROPIC MAINTENANCE 10-1. General. Arctic, desert, and tropic maintenance, inspections, and operations are explained In the following paragraphs. 10-2. Arctic Maintenance.  The following paragraphs contain  the  basic  principles  and  procedures  which  are essential  for  efficient  utilization  of  aircraft,  equipment, and personnel in arctic areas.  The operation of aircraft In arctic regions is seriously handicapped because of the effect of the elements on both personnel and equipment.        With    a    decrease    in    temperature,    an increase  In  time  required  to  perform  duties  is  inflicted due  to  reduced  flexibility  of  packings  and  rubber  parts, higher viscosity of lubricants, and binding of metal parts due  to  contraction.    General  procedures  for  all  aircraft are   discussed   within   these   paragraphs.      For   specific problems on a particular aircraft or piece of equipment, refer to the applicable maintenance manual. a. Precautions.          Maintenance     personnel     shall observe    the    following    precautions    as    a    guide    to successful performance of duty In severe weather. (1) Exercise  care  when  stepping  or  walking on    snow    or    frost-covered    or    very    cold    surfaces. Wearing  proper  shoes  will  aid  In  walking  on  slippery surfaces   and   reduce   the   possibility   of   injures   from slipping. (2) Exercise caution when touching very cold metal  with  bare  hands,  moisture  on  hands  will  tend  to freeze skin to metal.  When practical, wear gloves and cover metal tool handles (3) Do  not  exert  excessive  torque  or  tension on  bolts,  nuts,  cables,  or  similar  items  when  making repairs on equipment that has been exposed to extreme cold.      These   items   tend   to   freeze   or   snap   as   metal expands upon warming. b. Preheating.    The  following  paragraphs  explain general procedures for preheating aircraft and engines. CAUTION Do  not  permit  air  from  heaters  with temperature     In     excess     of     251^oF (122^oC)     to     blast     against     ignition harness,   flexible   hose,   self-sealing tanks,  or  other  rubberized  or  fabric materials.      Damage   may   otherwise result. (1) Preheat requirements.    Engine  preheat  is normally  required  only  on  reciprocating  engines.    Jet engines   do   not   require   preheat   unless   the   available auxiliary    power    unit    is    not    sufficient    to    overcome additional  starter  loads.    Preheat  requirements  can  be considerably   reduced   by   following   proper   oil   dilution procedures. (2) Preheat for starting .  At low temperature, apply  heat  to  engine  as  a  starting  aid.    Reduce  starter loads    by    preheating    engine,    thereby    reducing    oil viscosity.      Generally,   preheat   will   not   be   required   If temperature  is  above  0°F  (-180C)  and  engine  oil  has been properly diluted (3) Preheat  time.    Preheat  time  required  to prepare  an  engine  for  starting  depends  on  outside  air temperature, size of engine, heater output, and velocity and direction of wind.  Also, when oil dilution, method of preheat  application,  or  use  of  covers  and  nose  shields are  inefficiently  applied,  the  required  preheat  time  will be lengthened. (4) Preheat  application.    Apply  heat  to  both the  power  and  accessory  sections  until  cylinder  heat, temperature  reaches  68°F  (20°C).    Do  not  rely  entirely upon temperature gauge as readings may be misleading because of thermocouple being located in path of heater blast.  Where heater supply is limited, concentrate heat on rear accessory section, particularly main oil drain, oil lines,  and  oil  sump,  with  second  priority  going  to  nose gear, propeller hub, and power section. 10-1