## Subsystem FMsort

FMsort is a subsystem of the Beaver model, used to sort the different contributions to the external forces and moments which act upon the aircraft and to compute the total external forces and moments in the body-axes reference frame by summing the different contributions. Note: the aerodynamic forces and moments for the DHC-2 'Beaver' are expressed in the body-axes reference frame instead of the more common wind or flight-path axes. If aerodynamic lift and drag are used instead, it is necessary to implement the transformation equations in the equations for dV/dt, d(alpha)/dt, and d(beta)/dt and to change FMsort accordingly.

Currently, only four contributions to the external forces and moments, acting upon the aircraft, are taken into account: the aerodynamic forces and moments, propulsive forces and moments (including slipstream effects), forces due to the influence of gravity, and additional contributions due to non-steady atmosphere. It is not difficult to add more contributions to this list: just unmask the block FMsort to find out how it works.

### Inputvectors: FMaero, FMprop, Fgrav, Fwind

      FMaero = [Xa  Ya  Za  La  Ma  Na]'  (aerodynamic forces and mo-
                 ments, coming from the subsystem Aerodynamics Group)

      FMprop = [Xp  Yp  Zp  Lp  Mp  Np]'  (engine forces and moments,
                              coming from the subsystem Engine Group)

      Fgrav  = [Xgr Ygr Zgr]'        (gravity forces, coming from the
                                                       block Gravity)

      Fwind = [Xw  Yw  Zw]'        (wind forces from the block Fwind)

      Xa, Ya, Za   : aerodynamic forces in body-axes [N]
      La, Ma, Na   : aerodynamic moments in body-axes [Nm]
      Xp, Yp, Zp   : propulsive forces in body-axes [N]
      Lp, Mp, Np   : propulsive moments in body-axes [Nm]
      Xgr, Ygr, Zgr: gravity forces in body-axes [N]
      Xw, Yw, Zw   : wind forces in body-axes [N] (correction terms
                     for non-steady atmosphere, may also include the
                     influence of atmospheric turbulence)

### Outputvectors: Ftot and Mtot

      Ftot = [Fx Fy Fz]'                     (total body-axes forces)
      Mtot = [L  M  N ]'                    (total body-axes moments)

      Fx, Fy, Fz: total forces along the aircraft's body-axes [N]
      L, M, N   : total moments along the aircraft's body-axes [Nm]