TM  55-1510-221-10 8-69.  COLD  WEATHER  OPERATIONS. Operation of the surface deice system in ambient  temperatures  below  -40°C  can cause  permanent  damage  to  the  deice boots.   Operational   diffIculties   may   be encountered  during  extremely  cold weather,  unless  proper  steps  are  taken prior  to  or  immediately  after  flight.  All personnel should understand and be fully aware  of  the  necessary  procedures  and precautions involved. a.  Preparation  For  Flight.  Accumulations   of snow, ice, or frost on aircraft surfaces will adversely affect takeoff distance, climb performance and stall speeds to a dangerous degree. Such accumulations must  be  removed  before  flight.  In  addition  to  the normal exterior checks, following the removal of ice, snow,  or  frost,  inspect  wing  and  empennage  surfaces to  verify  that  these  remain  sufficiently  cleared.  Also, move all control surfaces to confirm full freedom of movement. Assure that tires are not frozen to wheel chocks or to the ground. Use ground heaters, anti- ice  solution,  or  brake  deice,  to  free  frozen  tires. When heat is applied to release tires, the tempera- ture  should  not  exceed  71  °C  (160°F).  Refer  to  Chap- ter  2  for  anti-icing,  deicing,  and  defrosting  treat- ment. b. Engine Starting. When starting engines on ramps  covered  with  ice,  propeller  levers  should  be  in the  FEATHER  position  to  prevent  the  tires  from sliding.  To  prevent  exceeding  torque  limits  when advancing CONDITION levers to HIGH IDLE dur- ing the starting procedure, place the power lever in BETA and the propeller lever in HIGH RPM before advancing the condition lever to HI IDLE. c. Warm-Up and Ground Test. Warm-up pro- cedures and ground test are the same as those out- lined in Section II. d.  Taxiing.  Whenever  possible,  taxiing  in deep snow, light weight dry snow or slush should be avoided, particularly in colder OAT conditions. If it is necessary to taxi through snow or slush, do not set the parking brake when stopped. If possible, do not park  the  aircraft  in  snow  or  slush  deep  enough  to reach  the  brake  assemblies.  Chocks  or  sandbags should be used to prevent the aircraft from rolling while  parked.  Before  attempting  to  taxi,  activate  the brake deice system, insuring that the bleed air valves are OPEN and that the condition levers are in HI IDLE.  An  outside  observer  should  visually  check wheel  rotation  to  insure  brake  assemblies  have  been deiced.  The  condition  levers  may  be  returned  to LOW IDLE as soon as the brakes are free of ice. e.  Before  Takeoff. (1.) If icing conditions are expected, acti- vate  all  anti-ice  systems  before  takeoff,  allowing  suf- ficient time for the equipment to become effective. (2.) If  the  possibility  of  ice  accumulation on  the  horizontal  stabilizer  or  elevator  exists,  takeoff will  not  be  attempted.  If  icing  conditions  are expected,  activate  all  anti-ice  systems  before  takeoff, allowing   sufficient   time   for   the   equipment   to become effective. f.  Takeoff.  Takeoff  procedures  for  cold weather  operations  are  the  same  as  for  normal  take- off. Taking off with temperatures at or below freez- ing, with water, slush or snow on the runway, can cause ice to accumulate on the landing gear and can throw  ice  into  the  wheel  well  areas.  Such  takeoffs shall be made with brake deice on and with the ice vanes  extended  to  preclude  the  possibility  of  ice build-up on engine air inlets. Monitor oil tempera- tures to insure operation within limits. Before flight into icing conditions, the pilot and copilot WSHLD ANTI-ICE switches should be set at NORMAL posi- tion. g.  During  Flight. (1.) Brake deice. After takeoff from a run- way covered with snow or slush, it may be advisable to leave brake deice ON to dislodge ice accumulated from the spray of slush or water. Monitor BRAKE DE-ICE  annunciator  for  automatic  termination  of system operation and then turn the switch OFF. (2.)   Flight   controls.   During   flight,   trim tabs and controls should also be exercised periodi- cally to prevent freezing. (3.) Anti-icing equipment. Insure that anti- icing  systems  are  activated  before  entering  icing  con- ditions.  Do  not  activate  the  surface  deice  system until ice has accumulated one-half to one inch. The propeller  deice  system  operates  effectively  as  an anti-ice system and it may be operated continuously in  flight.  If  propeller  imbalance  due  to  ice  does occur, it may be relieved by increasing RPM briefly, then  returning  to  desired  setting. 8-27