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be loaded into the MATLAB workspace from file, using TRILOAD (see section 12.4.2). Of
course, it is also possible to manually enter xinco, if required.
The vector xfix is optional: if this variable is not present in the workspace when the
aircraft model equations are evaluated, it will automatically be set to its default value
ones(1,12) by the block xfix (which is contained in the subsystem Aircraft Equations of
Motion (Beaver). If it is desired to artificially fix certain states, xfix should be entered
manually (it must be a vector of length 12, with all elements being either one or zero), or
by running the utility FIXSTATE (see section 12.6.2).
Connections
in: all input vectors are obtained from the interface level of the aircraft model (Beaver
level 1).
out: all output vectors from the aircraft model (except for some very trivial results such
as the help vector yhlp) are sent to the top-level of the aircraft model.
Type browse level2 at the command-line for on-line help.
142 Chapter 8. Aircraft model block reference
Dimless Beaver level 1 / Beaver level 2 / Aerodynamics Group / Dimless
Main FDC library / Aerodynamics
Type
Aircraft-independent masked subsystem block, essential for solving the equations of motion.
Description
The block Dimless is used to obtain dimensionless roll, pitch, and yaw rates, which are
required for the aerodynamic model of the Beaver. It should be noted that the equations
used to determine these dimensionless rotational velocities are typical for most models
developed by the Control and Simulation Division, Faculty of Aerospace Engineering,
Delft University of Technology. Other sources may use different expressions, so be careful
to verify these expressions before trying to implement a model of a different aircraft
within the FDC structure. The equations themselves are independent of the aircraft under
consideration.
Equations
The equations used by the block Dimless are straightforward:
• Non-dimensional roll rate:
p !
p b
2V
• Non-dimensional pitch rate:
q !
qc
V
• Non-dimensional yaw rate:
r !
r b
2V
Inputs
x = [ V a b p q r y q j xe ye H ]T state vector, x
Outputs
ydl = [ pb
2V
qc
V
rb
2V ]T non-dimensional angular velocities, ydl
Parameters
Dimless needs the parameter vector GM1 to be present the MATLAB workspace, in order
to extract the wing span b and mean aerodynamic chord c. The definition of GM1 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).
Connections
in: x comes from the block Integrator.
out: ydl is connected to the block Aeromod.
Type browse dimless at the command-line for on-line help.
8.2. The aircraft model block libraries 143
Engine Group (Beaver) Beaver level 1 / Beaver level 2 / Engine Group (Beaver)
Main FDC library / Engine forces and moments
Type
Aircraft-dependent subsystem, essential for solving the equations of motion. The subsystem
is not masked.
Description
The subsystem Engine Group (Beaver) contains blocks which determine the engine power
and compute the resulting forces and moments due to operation of the powerplant, including
contributions of the propeller slipstream to the aerodynamic forces and moments.
The subsystem is based on model data from ref.[34] (see also section 3.3.1), which is valid
for the DeHavilland DHC-2 Beaver aircraft. The remainder of the aerodynamic model
has been implemented in the subsystem Aerodynamics Group (Beaver).
Subsystems and/or blocks
The subsystem Engine Group (Beaver) contains three blocks:
Power computes the power of the engine and the dimensionless increase in air pressure
across the plane of the propeller,
Engmod computes dimensionless force and moment coefficients which are caused by
the operation of the powerplant, including propeller slipstream effects,
FMdims converts the dimensionless force and moment coefficients to dimensional forces
and moments.
Inputs
x = [ V a b p q r y q j xe ye H ]T state vector, x
uprop = [ n pz ]T external propulsion inputs, uprop
yatm = [ r ps T μ g ]T basic atmospheric properties, yatm
yad1 = [ a M qdyn ]T basic airdata variables, yad1
Outputs
ypow = [ dpt P ]T engine power related variables, ypow
Cprop = [ CXp CYp Czp Clp Cmp Cnp ]T propulsive force and moment coefficients, Cprop
FMprop = [ Xp Yp Zp Lp Mp Np ]T dimensional propulsive forces and moments, FMprop
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FDC 1.4 – A SIMULINK Toolbox for Flight Dynamics and Contro(71)
