## Subsystem Dimless

Dimless computes the dimensionless rotational velocities pb/2V, qc/V, and rb/2V. Of course, the computation itself is trivial if the elements of the state vector x are known, but since these variables may be needed more than once it is still useful to compute them in a separate block.

Dimless is contained in the subsystem Aerodynamics Group (Beaver) of the Beaver model. Other blocks in that subsystem are: Aeromod (Beaver) and FMdims.

### 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 state variables which are not actually needed by Dimless have been displayed between curly braces.

### Outputvector: ydl

      ydl = [pb/2V qc/V rb/2V]' (dimensionless rotational velocities).

      pb/2V: dimensionless roll-rate  (b = wing span)
      qc/V : dimensionless pitch-rate (c = cbar = mean aerodynamic chord)
      rb/2V: dimensionless yaw-rate   (b = wing span)

### Parameters to be defined in the Matlab workspace

- GM1: vector with some important geometrical properties of the 'Beaver' aircraft, and the mass of the aircraft (which is assumed to be constant during the motions of interest). Here, the wing span b and the mean aerodynamic chord cbar are extracted from GM1. GM1 can be loaded into the workspace from file by running the utility DATLOAD. Run MODBUILD first if the datafile does not yet exist.