## Subsystem Cwind: constant wind

Cwind is a masked Simulink system, which is used to calculate velocity components along the body-axes of the aircraft, assuming a constant wind speed and direction. If you want the wind velocity and/or direction to vary with altitude, use BLwind instead. Both Cwind and BLwind are contained in the blocklibrary WINDLIB.

The user must specify the wind velocity Vw in [m/s], the horizontal wind direction psi_w in [rad], and the vertical wind direction gamma_w, also in [rad]. Notice that psi_w should be equal to pi rad if the wind is blowing to the North and that gamma_w is positive for upward blowing wind!

### Inputvector: x

      x = [V alpha beta p q r psi theta phi xe ye H]'        (states)

     {V    : airspeed [m/s]                                         }
     {alpha: angle of attack [rad]                                  }
     {beta : sideslip angle [rad]                                   }
     {p    : roll rate [rad/s]                                      }
     {q    : pitch rate [rad/s]                                     }
     {r    : yaw rate [rad/s]                                       }
      psi  : yaw angle [rad]
      theta: pitch angle [rad]
      phi  : roll angle [rad]
     {xe   : x-coordinate in Earth-fixed reference frame [m]        }
     {ye   : y-coordinate ''     ''          ''      ''  [m]        }
     {H    : altitude above sea-level [m]                           }

The variables which are not actually used by Cwind have been displayed between curly braces.

### Outputvector: ywind

      ywind = [uw vw ww]'

      uw   : wind velocity component along XB-axis [m/s]
      vw   : wind velocity component along YB-axis [m/s]
      ww   : wind velocity component along ZB-axis [m/s]