TM  55-1510-221-10 NOTE Do not operate deicer boots continuously. Continuous   operation   tends   to   balloon the ice over the boots. Allow at least 1/2 inch  of  ice  to  accumulate  on  the  surface boots  and  1/8  to  1/4  inch  of  ice  to  accu- mulate  on  the  antenna  boots,  then  acti- vate  the  deicer  boots  to  remove  the  ice. Repeat this procedure as required. (4.) Ice vanes. Ice vanes must be extended when operating in visible moisture or when freedom from  visible  moisture  cannot  be  assured,  at  5°C OAT  or  less.  Ice  vanes  are  designed  as  an  anti-ice system,  not  a  deice  system.  After  the  engine  air  inlet screens are blocked, lowering the ice vanes will not rectify the condition. Ice vanes should be retracted at 15°C OAT and above to assure adequate engine oil  cooling. (5.) Stall speeds. 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 com- fortable margin of airspeed above the normal stall airspeed. Maintain a minimum of 140 KIAS during sustained icing conditions to prevent ice accumula- tion  on  unprotected  surfaces  of  the  wing.  In  the event  of  windshield  icing,  reduce  airspeed  to  226 KIAS or below. h. Descent. Use normal procedures in Section II. Brake icing should be considered if moisture was encountered  during  previous  ground  operations  or inflight in icing conditions with gear extended. i. Landing. Landing on an icy runway should be  attempted  only  when  absolutely  necessary  and should not be attempted unless the wind is within 10  degrees  of  runway  heading.  Application  of  brakes without  skidding  the  tires  on  ice  is  very  difficult, due to the sensitive brakes. In order not to impair pilot  visibility,  reverse  thrust  should  be  used  with caution  when  landing  on  a  runway  covered  with snow or standing water. Use the procedures in Sec- tion II for normal landing. j. Engine Shutdown. Use normal procedures in Section II. k. Before Leaving the Aircraft. When the air- craft  is  parked  outside  on  ice  or  in  a  fluctuating freeze-thaw   temperature   condition   the   following procedures  should  be  followed  in  addition  to  the normal procedures in Section II. After wheel chocks are in place, release the brakes to prevent freezing. Fill  fuel  tanks  to  minimize  condensation,  remove any  accumulation  of  dirt  and  ice  from  the  landing 8-28 gear  shock  struts,  and  install  protective  covers  to guard against possible collection of snow and ice. 8-70. DESERT OPERATION AND HOT WEATHER OPERATION. Dust, sand, and high temperatures encountered during  desert  operation  can  sharply  reduce  the  oper- ational  life  of  the  aircraft  and  its  equipment.  The abrasive  qualities  of  dust  and  sand  upon  turbine blades  and  moving  parts  of  the  aircraft  and  the destructive  effect  of  heat  upon  the  aircraft  instru- ments will necessitate hours of maintenance if basic preventive measures are not followed. In flight, the hazards of dust and sand will be difficult to escape, since dust clouds over a desert may be found at alti- tudes up to 10,000 feet. During hot weather opera- tions, the principle difficulties encountered are high turbine  gas  temperatures  (TGT)  during  engine  start- ing, over-heating of brakes, and longer takeoff and landing rolls due to the higher density altitudes. In areas  where  high  humidity  is  encountered,  electrical equipment (such as communication equipment and instruments)  will  be  subject  to  malfunction  by  corro- sion, fungi and moisture absorption by nonmetallic materials. a. Preparation For Flight. Check the position of the aircraft in relation to other aircraft. Propeller sand blast can damage closely parked aircraft. Check that the landing gear shock struts are free of dust and  sand.  Check  instrument  panel  and  general  inte- rior  for  dust  and  sand  accumulation.  Open  main entrance  door  and  cockpit  vent  storm  windows  to ventilate  the  aircraft. N1  speeds  of  70%  or  higher  may  be required  to  keep  oil  temperature  within limits. b. Engine Starting. Use normal procedures in Section II. Engine starting under conditions of high ambient  temperatures  may  produce  a  higher  than normal  TGT  during  the  start.  The  TGT  should  be closely  monitored  when  the  condition  lever  is moved to the LO IDLE position. If overtemperature tendencies   are   encountered,   the   condition   lever should  be  moved  to  the  IDLE  CUTOFF  position periodically  during  acceleration  of  gas  generator RPM  (N1).  Be  prepared  to  abort  the  start  before temperature  limitations  are  exceeded. c. Warm-Up Ground Tests. Use normal proce- dures  in  Section  II.  To  minimize  the  possibility  of damage  to  the  engines  during  dusty/sandy  condi-