NAVWEPS 00-BOT-RO  BASIC AERODYNAMICS  fuel.  Hence, the gross weight and stall speed  of the airplane can vary considerably through-  out the flight.  The effect of only weight on  stall speed can be expressed  by a modified form  of the stall speed equation where density ratio,  c r,,,.,,  and wing area are held constant.  It is frequently stated that the career Naval  Aviator spends more than half his life “below  a thousand feet and a hundred knots.”  Re-  gardless of the implications of such a state-  ment, the thought does cunnute the relation-  ship of minimum flying speeds and carrier  aviation.  Only in Naval Aviation is there  such importance assigned to precision control  of the aircraft at high lift conditions.  Safe  operation in carrier aviation demands precision  control of the airplane at high lift conditions.  The aerodynamic lift characteristics of an  airplane are portrayed by the curve of lift  coefficient versus angle of attack.  Such a  curve is illustrated in figure 1.15 for a specific  airplane in the clean and flap down configura-  tions. A given aerodynamic configuration ex-  periences increases in lift coefficient with in-  creases  in angle of attack until the maximum  lift coefficient is obtained.  A further increase  in angIe of attack produces stall and the lift  coefficient then decreases. Since the maximum  lift coefficient corresponds to the minimum  speed available in flight, it is an important  point of reference.  The stall speed of the air-  craft in level flight is related by the equation:  As an illustration of this equation, assume  that a particular airplane has a stall speed of  100 knots at a gross weight of 10,000 lbs.  The stall speeds  of this Sam: airplane at other  gross weights would be:  where  V*,=stall speed corresponding to some  gross weight, WI  V@a=  stall speed corresponding to a dif-  ferent gross weight, WP  Figure 1.15 illustrates the effect of weight on  stall speed on a percentage basis and will be  valid for any airplane. Many specific condi-  tions of flight are accomplished at certain fixed  angles of attack and lift coefficients.  The  effect of weight on a percentage basis on the  speeds  for any specific lift coefficient and angle  of attack is identical.  Note that at small  variations of weight, a rule of thumb may  express the effect of weight on stall speed-  “a 2 percent change in weight causes  a I per-  cent change in stall speed.”  This equation illustrates the effect on stall  speed of weight and wing area (or wing load-  ing, W/S), maximum lift coefficient, and alti-  tude. If the stall speed is desired in EAS, the  density ratio will  be that for sea level (u=  1.000).  EFFECT OF WEIGHT.  Modern configu-  rations of airplanes are characterized  by a large  percent. of the maximum gross weight being  Turning flight  and maneuvers produce an  effect on stall speed which is similar to the  effect of weight.  Inspection of the chart on  figure 1.16 shows the forces  acting on an airplane  in a steady turn.  Any steady turn requires  that the vertical component of Iift be equal to  V.-stall  speed, knots TAS  W=gross weight, lbs.  c Lnoz=  airplane maximum lift coefficient  csaltitude density ratio  S= wing area, sq. ft.  where  V7.=17.2  J--  c w  .ln2s  ll,W  100x  4,  ‘ &~=lO,  12,ooO  110  14,4al  120  9mJ  95  8,100  90  EFFECT OF MANEUVERING  FLIGHT.  35  V  _i_z-  K  J  v.,-  K  PLIGHT AT HIGH LIFT CONDITIONS 