NAVWEPS OO-BOT-80  BASIC AE,RODYNAMlCS  (C) The point of minimum total drag occurs  at a speed of 163 knots. Since this speed in-  curs the least total drag for lift-equal-weight  flight, the airplane is operating at (L/D)ma,.  Because of the particular manner in which  parasite and induced drags vary with speed  (parasite drag directly as the speed squared;  induced drag inversely as the speed squared)  the minimum total drag occurs when the in-  duced and parasite drags are equal.  The speed  for minimum drag is an important reference  for  many items of airplane performance.  One  item previously ,presented related glide per-  formance and lift-drag ratio.  At the speed of  163 knots this airplane incurs a total drag of  778 lbs. while producing 12,000 lbs. of lift.  These figures indicate a maximum lift-drag  ratio of 15.4.and relate a glide ratio of 15.4.~  In addition, if this airplane were jet powered,  the airplane would achieve maximum en-  durance at this airspeed for  ‘ the specified alti-  tude. If this airplane were propeller powered,  the airplane would achieve maximum range at  this airspeed  for the specified  altitude.  215 knots. This point on the drag curve pro-  duces the highest proportion between velocity  and drag and would be the point for maximum  range if the airplane were jet powered. Be-  cause of the high proportion of parasite drag  at this point the long range jet airplane has  great preference  for great aerodynamic clean-  ness and less demand for a high aspect ratio  than the long range propeller powered airplane.  (E) At a speed of 400 knots, the induced  drag is an extremely small part of the total  drag and parasite drag predominates.  (P) As the airplane reaches  very high flight  speeds, the drag rises in a very rapid fashion  due to compressibility. Since the generalized  equation for parasite drag does not account for  compressibility effects, the actual drag rise is  typified by the dashed line.  The airplane drag curve shown in figure 1.34  is particular to one weight, configuration, and  altitude in level flight.  Any change in one of  these variables will affect the specific drags at  specific  velocities.  The airplane drag curve is a major factor in  many items of airplane performance.  Range,  endurance, climb, maneuver, landing, takeoff,  etc., performance  are based on some relation-  ship involving the airplane drag curve.  (D) Point (D) is at an airspeed approxi-  mately 32 percent greater than the speed for  (L/D),.,.  Note that the parasite drag com-  prises 75 percent of the total drag at a speed of  94 