NAVWEPS OD-SOT-80  APPLICATION OF AERODYNAMICS,  TO SPECIFIC PROBLEMS OF FLYING  length.  Familiarity with the airplane hand-  book performance  data and proper accounting  of weight, wind, altitude, temperature, etc.,  are necessary  parts of flying.  Conditions of  high gross weight, high pressure  altitude and  temperature, and unfavorable winds create the  extreme requirements of runway length, espe-  cially for the turbine powered airplane. Under  these conditions, use of the handbook data is  mandatory and no guesswork can be tolerated.  airplane.  Density altitude will  determine  the true airspeed at takeoff and can affect  the takeoff acceleration by altering the  powerplant thrust.  The effect of tempeta-  ture alone is important in the case of the  turbine powered aircraft since inlet air tem-  perature will affect powerplant thrust.  Ic  should be noted that a typical turbojet ait-  plane may he approximately twice as sensi-  tive to density altitude and five to ten times  as sensitive to temperature as a representa-  cive reciprocating engine powered airplane.  (4) Specific humidity must be accounted  for in the case of the reciprocating engine  powered airplane.  A high water vapor  content in the air will cause a definite reduc-  tion in takeoff power and takeoff acceler-  ation.  One typical.etror of takeoff technique is the  premature or excess  pitch rotation of the air-  plane.  Premzture  or excm pitch rotation of the  airplane may seriously reduce the takeoff accel-  eration and increase the takeoff distance. In  addition, when the airplane is placed at an  excessive  angle of attack during takeoff, the  airplane may become airborne at too low a  speed and the result may be a stall, lack of ade-  quate control (especially in a crosswind), or  poor initial climb performance. In fact. there  are certain low aspect ratio configurations of  airplanes which, at an excessive angle of ar-  tack, will not fly out of ground effect. Thus,  over-rotation of the airplane ,during takeoff  may hinder takeoff acceleration or the.initial  climb. It is quite typical for an airplane to be  placed at an excess  angle of attack and become  airborne prematurely then settle back fo rhe  runway.  When the proper angle of attack is  assumed,  the airplane simply accelerates  to the  takeoff speed and becomes airborne wirh suf-  ficient initial rate of climb.  In this sense, the  appropriate rotation and takeoff speeds or an  angle of attack indicator must be used.  (5) The runluay condition  will deserve con-  sideration when the takeoff acceleration is  basically low.  The runway slope must be  compared carefully with the surface winds  because  ordinary values of runway slope will  usually favor choice of the runway with  headwind and upslope rather than down-  slope and tailwind.  The surface condition  of the runway has little bearing on takeoff  distance as long as the runway is a hard  surface.  Each .of these factors must be accounted  for and the takeoff distance properly com-  puted for the existing conditions.  Since  obstacle clearance distance is generally a  function of the same factors which affect  takeoff distance, the obstacle clearance dis-  tance is usually related as some proportion  of the takeoff distance.  Of course, the take-  off and obstacle clearance distances related  by the handbook data will be obtained by  the techniques and procedures  outlined in the  handbook.  If the airplane is subject to a sudden  pull-up  or Jteep tzzra  after becoming airborne, rhe,resulr  may be a stall, spin, or reduction in initial rate  of climb.  The increased angle of attack may  exceed the critical angle of attack or the in-  crease  in induced drag may be quite large.  For  this reason, any clearing turns made immedi-  ately after takeoff or deck launch must be slight  and well within  the capabilities of the air-  plane.  TYPICAL ERRORS. The takeoff distance  of an airplane should be computed for each  takeoff.  A most inexcusable error would be to  attempt takeoff from a runway of insufficient  366 