text: When the airyJane is in steady, level flight, 
  the condition of equilibrium must prevail. 
  is 
  The unaccelerated condition of 
  achieved with 
  the airplane trimmed for lift 
  equal to weight and the powerplant set for a 
  In certain 
  thrust to equal the airplane drag. 
  conditions of airplane performance it is con- 
  venient to consider the airplane requirements 
  by the thnr$t required (or drag) while in other 
  is more applicable to consider the 
  cases it 
  power re@red. Generally, the jet airplane will 
  require consideration of the thrust required 
  and the propeller airplane will require consid- 
  eration of the power required. Hence, the 
  airplane in steady level flight will require lift 
  equal to weight and thrust available equal to 
  thrust required (drag) or power available equal 
  to power required. 
  
  flight 
  
  The variation of power required and thrust 
  required with velocity is illustrated in figure 
  2.20. Each specific curve of power or thrust 
  required is valid for a particular aerodynamic 
  configuration at a given weight and altitude. 
  These curves define the power or thrust re- 
  quired 
  Jift-equal- 
  weight, constant altitude 
  flight at various 
  airspeeds. As shown by the curves of figure 
  is desired to operate the airplane at 
  2.20, ifit 