## Subsystem Fwind

Fwind computes the contributions to the external forces along the body-axes in non-steady atmosphere (i.e., forces due to non-constant wind and/or atmospheric turbulence). See the descriptions of Cwind, BLwind, Turb1, and Turb2 for more information about the generation of the wind and turbulence velocities and their time-derivatives. The outputs from Fwind are sent to the block FMsort.

### Inputvectors: x and uwind

      x     = [V alpha beta p q r psi theta phi xe ye H]'    (states)
      uwind = [uw vw ww uwdot vwdot wwdot]' (wind + turbulence velo-
                                            cities and accelerations)

     {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]                           }

      uw   : wind + turbulence velocity along the XB-axis [m/s]
      vw   : wind + turbulence velocity along the YB-axis [m/s]
      ww   : wind + turbulence velocity along the ZB-axis [m/s]
      uwdot: d(uw)/dt [m/s^2]
      vwdot: d(vw)/dt [m/s^2]
      wwdot: d(ww)/dt [m/s^2]

The variables which are not actually needed by Fwind have been displayed between curly braces.

### Outputvector: Fwind

      Fwind = [Xw Yw Zw]'.

    where:

      Xw, Yw, Zw: forces due to non-steady atmosphere, measured along
                  the aircraft's body-axes [N]

### Parameters to be defined in the Matlab workspace

GM1: vector with some important geometrical properties of the 'Beaver' aircraft, and its mass (which is assumed to be constant during the motions of interest). Here, the mass m is extracted from GM1. GM1 can be loaded from file by running the utility DATLOAD. Run MODBUILD first if the datafile does not yet exist.