TM   1-1510-223-10 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   normaI   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.   Maintaina 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.    Taxing.    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 continously.   Allow   at   least   0.5   inch   of   ice   on   the   wing deicer boots or 0.25 inch on the antenna deicer boots before activating   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. 8-51A.  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 enviromnent  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   5-33A),   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 extended   exposure   to   flight   conditions   more   severe   than those for which the airplane has been certificated. (b)    Avoid   abrupt   and   excessive   maneuvering that  may  exacerbate  control  difficulties. (c)  Do  not  engage  the  autopilot. (d)    If  the  autopilot  is  engaged,  hold  the  control wheel firmly and disengage the autopilot. (e) If an unusual roll response or uncommanded   roll   control   movement   is   observed   reduce the  angle-of-attack. Change   1   8-33