## Subsystem Aeromod (Beaver)

Aeromod (Beaver) determines the aerodynamic force and moment coefficients for the DHC-2 'Beaver'. The aerodynamic model is aircraft-dependent, hence, this block must be replaced if models of other aircraft are to be implemented in the simulation structure of FDC.

Instant replacement of the block Aeromod (Beaver) is possible only if the same inputs and outputs to and from this block remain the same. However, the internal structure of a replacement for the current block Aeromod may look completely different. For instance, the aerodynamic model of the DHC-2 'Beaver', contained in Aeromod (Beaver) determines the force and moment coefficients by means of evaluation of six polynomial equations (see ref.[1]), whereas it is more customary to compute aerodynamic forces and moments by means of interpolation in large multi-dimensional tables.

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

Note: The side-force coefficient with respect to beta-dot has been neglected in the block Aeromod (Beaver), because it would have yielded an algebraic loop. Therefore, the beta-dot equation has been written out as an explicit equation with an aircraft-independent and an aircraft-dependent term. The latter is evaluated in a separate block xdotcorr (Beaver), which is contained in the subsystem Aircraft Equations of Motion.

### Inputvectors: x, uaero, ydl

      x    = [V alpha beta p q r psi theta phi xe ye H]'     (states)
      uaero= [deltae deltaa deltar deltaf]'      (aerodynamic inputs)
      ydl  = [pb/2V qc/V rb/2V]'           (dimensionless velocities,
                                       computed in the block Dimless)

     {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]                           }

      deltae: elevator deflection [rad]
      deltaa: deflection of the ailerons [rad]
      deltar: rudder deflection [rad]
      deltaf: flap setting [rad]

      pb/2V: dimensionless roll rate [-]
      qc/V : dimensionless pitch rate [-]
      rb/2V: dimensionless yaw rate [-]

The inputvariables which are not actually used by Aeromod (Beaver) have been displayed between curly braces.

### Outputvector: Caero

      Caero = [CXa CYz CZa Cla Cma Cna]'

      CXa, CYa, CZa: dimensionless aerodynamic force coefficients
      Cla, Cma, Cna: dimensionless aerodynamic moment coefficients.

### Parameters, which must be defined in the Matlab Workspace

- AM: matrix with stability and control derivatives of the 'Beaver' (valid only for the nonlinear aerodynamic model of the DHC-2 'Beaver', see ref.[1]). The matrix AM can be loaded into the Matlab workspace from file by running DATLOAD. Run MODBUILD first if this datafile does not yet exist.

### References

1. R.T.H. Tjee and J.A. Mulder. Stability and Control Derivatives of the De Havilland DHC-2 "Beaver" aircraft. Report LR-556, Delft University of Technology, 1988.