## Subsystem Flpath

Flpath computes some flight-path related parameters. Since the outputvariables from Flpath are not needed for solving the equations of motion themselves, this block has been included in the subsystem Additional Outputs. It is therefore possible to delete the block Flpath from the Beaver model if desired, but in that case the connections to the Outport and To Workspace blocks need to be checked.

### Inputvectors: x, xdot, and yhlp

      x    = [V alpha beta p q r psi theta phi xe ye H]'     (states)
      xdot = dx'/dt                 (time derivative of state vector)
      yhlp = [cos(alpha) sin(alpha) cos(beta) sin(beta) ...
              ... tan(beta) sin(psi) cos(psi) sin(theta) ...
              ... cos(theta) sin(phi) cos(phi)]'
                    (sines and cosines, coming from the block Hlpfcn)

      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 needed by Flpath have been displayed between curly braces. Of the vector xdot, the time derivatives of V and H are used, while yhlp is needed for the variables sin(phi) and cos(theta).

### Outputvector: yfp

      yfp = [gamma fpa chi Phi]'

      gamma: flightpath angle in [rad]
      fpa  : flightpath acceleration in [m/s^2]
      chi  : azimuth angle in [rad]
      Phi  : bank angle in [rad]