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Parameters
FMdims reads the parameter vector GM1 from the MATLAB workspace, in order to extract
the mean aerodynamic chord c, the wing span b, and the wing surface S. See appendix C
for the exact definition of GM1. This vector can be loaded from the file AIRCRAFT.DAT,
using the utility DATLOAD (see section 12.4.2). If this datafile has somehow inadvertently
been deleted, it can be re-created by running the program MODBUILD (see section 12.6.1).
Connections
in: yad1 comes from the block Airdata1; Caero comes from Aeromod (Beaver); Cprop comes
from Engmod (Beaver).
8.2. The aircraft model block libraries 149
out: FMaero or FMprop are connected to FMsort.
Type browse fmdims at the command-line for on-line help.
150 Chapter 8. Aircraft model block reference
FMsort Beaver level 1 / Beaver level 2 / FMsort
Main FDC library / Other (output-) equations
Type
Aircraft-independent masked subsystem block, essential for solving the equations of motion.
Description
The block FMsort is used to determine the sum of all contributions to the external forces
and moments, and sort the results in a force-vector and moment-vector. The FDC model
of the Beaver aircraft takes into account aerodynamic forces and moments, propulsive
forces and moments, gravitational forces, and wind-corrections. These contributions are
determined by the blocks Aerodynamics Group (Beaver), Engine Group (Beaver), Gravity,
and Fwind, respectively. It is relatively straightforward to include additional terms, such
as landing gear forces or forces caused by sudden weight-changes of the airplane, by
including the appropriate submodels and editing FMsort accordingly.
Equations
The equations used by the block FMsort are straightforward:
• Resulting forces along the body-axes, [N]:
Fx = Xa + Xp + Xgr + Xw
Fy = Ya +Yp +Ygr +Yw
Fz = Za + Zp + Zgr + Zw
• Resulting moments around the body-axes, [Nm]:
L = La + Lp
M = Ma + Mp
N = Na + Np
Inputs
FMaero = [ Xa Ya Za La Ma Na ]T dimensional aerodynamic forces and moments, FMaero
FMprop = [ Xp Yp Zp Lp Mp Np ]T dimensional propulsive forces and moments, FMprop
Fgrav = [ Xgr Ygr Zgr ]T gravity force components along body-axes, Fgrav
Fwind = [ Xw Yw Zw ]T corrections to body-axes forces in nonsteady atmosphere, Fwind
Outputs
Ftot = [ Fx Fy Fz ]T total external forces, Ftot
Mtot = [ L M N ]T total external moments, Mtot
Parameters
None.
Connections
in: FMaero comes from the block Aeromod (Beaver); FMprop comes from the block Engmod
(Beaver); Fgrav comes from Gravity; Fwind comes from Fwind.
out: Ftot and Mtot are both connected to Vabdot, pqrdot, Eulerdot, and xyHdot; Ftot is also
connected to Accel.
Type browse fmsort at the command-line for on-line help.
8.2. The aircraft model block libraries 151
Fwind Beaver level 1 / Beaver level 2 / Fwind
Main FDC library / Gravity and wind forces
Type
Aircraft-independent masked subsystem block, necessary for solving the equations of
motion in a nonsteady atmosphere.
Description
The block Fwind is used to compute correction terms for the external forces, which need to
be added to the forces along the aircraft’s body-axes when considering flight in nonsteady
atmosphere. These correction terms depend upon the components of the wind velocity
vector Vw along the aircraft’s body-axes, the time-derivatives of these wind components,
and the roll, pitch, and yaw rates of the aircraft.
Equations
The equations used by the block Fwind have been discussed in some more detail in section
3.3.4.
• Corrections to the force components along the body-axes, to account for nonsteady
atmosphere, [N]:
Xw = −m(u˙w + qww − rvw)
Yw = −m(v˙w − pww + ruw)
Zw = −m(w˙ w + pvw − quw)
Inputs
x = [ V a b p q r y q j xe ye H ]T state vector, x
uwind = [ uw vw ww u˙w v˙w w˙ w ]T body-axes components of the wind velocity,
and their time-derivatives, uwind
Outputs
Fwind = [ Xw Yw Zw ]T corrections to body-axes forces in nonsteady atmosphere, Fwind
Parameters
Fwind needs the parameter vector GM1 to be present the MATLAB workspace, in order
to extract the mass m of the aircraft (the mass has been implemented as a parameter, i.e.
it is assumed to be constant during the relative short time intervals considered). The
definition of this vector can be found in appendix C. GM1 can be loaded from the file
AIRCRAFT.DAT, using the utility DATLOAD (see section 12.4.2). If this datafile has somehow
inadvertently been deleted, it can be re-created by running the program MODBUILD
(see section 12.6.1).
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FDC 1.4 – A SIMULINK Toolbox for Flight Dynamics and Contro(74)
