text: pressure, q. The pressure gauge is then cali- 
  brated to indicate flight speed in the standard 
  sea level air mass. For example, a dynamic 
  pressure of 305 psf would be realized at a sea 
  level flight ,speed of 300 knots. 
  
  surface anflow continues to the aft stagnation 
  point where the local velocity is again zero. 
  The important point of this example of aero- 
  dynamic flow is existence of the stagnation 
  point. The change in airflow static pressure 
  which takes place at the stagnation point IS 
  equal to the free stream dynamic pressure, q. 
  The measurement of free stream dynamic 
  pressure is fundamental to the indication of 
  In fact, airspeed indicators are sim- 
  airspeed. 
  ply pressure gauges which measure dynamic 
  pressure related to various airspeeds. Typical 
  in 
  airspeed measuring systems are illustrated 
  figure 1.5. The pitot head has no internal 
  flow velocity and the pressure in the pitot tube 
  is equal to the total pressure of the airstream. 
  The purpose of the static-ports is to sense the 
  true static pressure of the free airstream. The 
  total pressure and static pressure lines are 
  attached to a differential pressure gauge and 
  is the dynamic 
  the net pressure indicated 
  
  there can be many conditions of 
  flight where the airspeed indicator does not 
  truly reflect the actual velocity through 
  the 
  air mass. The corrections that must be applied 
  are many and lisred in sequence below: 
  (1) The indicated airspeed (IAS) 
  
  Actually 
  
  is the 
  actual instrument indication for some given 
  flight condition. Factors such as an altitude 
  other than standard sea level, errors of the 
  instrument and errors due to the installation, 
  compressibility, etc. may create great vari- 
  ance between this instrument indication and 
  the actual flight speed. 
  
  (2) The calibrated airspeed (CM) 