TM  55-1510-221-10 icing condition entry speed to the indicated speed after a surface  and  antenna  deice  cycle  is  completed. (4)  Any  variations  from  normal  indicated  airspeed between  the  pilot’s  and  copilot’s  airspeed  indicators. a. Typical Ice. Icing occurs because of supercooled water vapor such as fog, clouds or rain. The most severe icing occurs on aircraft surfaces in visible moisture or precipitation  with  a  true  outside  air  temperature  between -5°C and +1°C; however, under some circumstances. dangerous  icing  conditions  may  be  encountered  with temperatures below -10°C. The surface of the aircraft must  be  at  a  temperature  of  freezing  or  below  for  it  to  stick. If  severe  icing  conditions  are  encountered,  ascend  or descend to altitudes where these conditions do not prevail. If flight into icing conditions is unavoidable, proper use of aircraft  anti-icing  and  deicing  systems  may  minimize  the problems encountered. Approximately 15 minutes prior to flight into temperature conditions which could produce frost  or  icing  conditions,  the  pilot  and  co-pilot  windshield anti-ice   switches   should   be   set   at   normal   or   high temperature position (after preheating) as necessary to eliminate windshield ice. Stalling  airspeeds  should  be expected to increase when ice has accumulated on the aircraft causing distortion of the wing airfoil. For the same reason. stall warning devices are not accurate and should not  be  relied  upon.  Keep  a  comfortable  margin  of  airspeed above the normal stall airspeed with ice on the aircraft. Maintain  a  minimum  of  140  knots  during  sustained  icing conditions to prevent ice accumulation on unprotected surfaces  of  the  wing.  In  the  event  of  windshield  icing, reduce  airspeed  to  226  knots  or  below. b. Rain. Rain presents no particular problems other than  restricted  visibility  and  occasional  incorrect  airspeed indications. c. Taxiing. Extreme care must be exercised when taxiing on ice or slippery runways. Excessive use of either brakes  or  power  may  result  in  an  uncontrollable  skid. d. Takeoff.  Extreme care must be exercised during takeoff from ice or slippery runways. Excessive use of either  brakes  or  power  may  result  in  an  uncontrollable  skid. e. Climb. Keep  aircraft  attitude  as  flat  as  possible  and climb with higher airspeed than usual, so that the lower surfaces of the aircraft will not be iced by flight at a high angle  of  attack. f.  Cruise  Flight. (1) Prevention of ice formation. Prevention of ice formation  is  far  more  effective  and  satisfactory  than attempts to dislodge the ice after it has formed. If icing conditions are inadvertently encountered, turn on the anti- icing systems prior to the first sign of ice formation. (2)  Deicer  boots.  Do  not  operate  deicer  boots continuously. Allow at least one-half inch of ice on the boots before activating the deicer boots to remove the ice. Continued  flight  in  severe  icing  conditions  should  not  be attempted. If ice forms on the wing area aft of the deicer boots,  climb  or  descend  to  an  altitude  where  conditions  are less severe. g. Landing.  Extreme care must be exercised when landing on ice or slippery runways. Excessive use of either brakes  or  power  may  result  in  an  uncontrollable  skid.  Ice accumulation on the aircraft will result in higher stalling airspeeds  due  to  the  change  in  aerodynamic  characteristics and increased weight of the aircraft due to ice buildup. Approach  and  landing  airspeeds  must  be  increased accordingly. NOTE When operating on wet or icy runways, refer to stopping  distance  factors  shown  in  Chapter  7. 8-72A.   ICING   (SEVERE). a.  The following weather conditions may be conducive to severe in-flight icing: (1) Visible rain at temperatures below zero degrees Celsius  ambient  air  temperature. (2) Droplets that splash or splatter on impact at temperatures below zero degrees Celsius ambient air temperature. b.  The  following  procedures  for  exiting  a  severe  icing environment  are  applicable  to  all  flight  phases  from  takeoff to  landing. (1)  Monitor  the  ambient  air  temperature.  While severe icing may form at temperatures as cold as -18 degrees  Celsius, increased  vigilance  is  warranted  at temperatures  around  freezing  with  visible  moisture  present. (2) Upon observing the visual cues specified in the limitations section of the airplane flight manual (Military Operations Manual) for the identification of severe icing conditions  (reference  paragraph  5-30B.),  accomplish  the following: (a)  Immediately  request  priority  handling  from air traffic control to facilitate a route or an altitude change to  exit  the  severe  icing  conditions  in  order  to  avoid 8-28.2  Change  5