📄 fmdims.htm

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      FDC help: FMdims
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    <h2>
      Subsystem <i>FMdims</i>
    </h2>
    <p><i>FMdims</i> computes forces in
    [<i>N</i>] and moments in [<i>Nm</i>] from dimensionless force and moment
    coefficients, using the dynamic pressure and some geometric properties of
    the aircraft, see the <a href="#Equations">equations</a> below. In the
    <a href="beaver.htm">&#39;Beaver&#39; model</a>, <i>FMdims</i> is used by the subsystem blocks <i><a
    href="aerogrp.htm">Aerodynamics Group (Beaver)</a></i> and <i><a href=
    "enggrp.htm">Engine Group (Beaver)</a></i> of the <i><a href="beaver.htm">Beaver</a></i> model, where it is being applied to aerodynamic
    forces and moments and propulsive forces and moments, respectively. (In
    those subsystems, the non-dimensional coefficients are computed within the
    blocks <i><a href="aeromod.htm">Aeromod</a></i> and <i><a href=
    "engmod.htm">Engmod</a></i>.)</p> 
    <h3>
      Inputvectors: <i>yad1</i> and <i>Caero</i> or <i>Cprop</i>
    </h3>
<pre>
  yad1 = [a M qdyn]&#39;                (airdata variables which are
                                  computed in the block <a href=
"airdata1.htm">Airdata1</a>)

  Caero= [CXa CYa CZa Clt Cma Cna]&#39;   (dimensionless aerodynamic
                                   force and moment coefficients,
                                    computed in <a href=
"aeromod.htm">Aeromod (Beaver)</a>)

  Cprop= [CXp CYp CZp Clp Cmp Cnp]&#39;    (dimensionless propulsive
                                   force and moment coefficients,
                                     computed in <a href=
"engmod.htm">Engmod (Beaver)</a>)

 {a    : speed of sound [m/s]                                   }
 {M    : Mach number [-]                                        }
  qdyn : dynamic pressure [N/m^2]

  CXa, CYa, CZa: aerodynamic force coefficients along the 
                 aircraft&#39;s body-axes
  Cla, Cma, Cna: aerodynamic moment coefficients along the 
                 aircraft&#39;s body-axes
  CXp, CYp, CZp: engine force coefficients along the aircraft&#39;s
                 body-axes
  Clp, Cmp, Cnp: engine moment coefficients along the air-
                 craft&#39;s body-axes
</pre>
    <p>The inputvariables which are not actually used by <i>FMdims</i> have been
    displayed between brackets.</p> 
    <h3>
      Outputvector: <i>FMaero</i> or <i>FMprop</i>
    </h3>
<pre>
  FMaero= [Xa Ya Za La Ma Na]&#39; (vector with aerodynamic forces &amp; moments)
  FMprop= [Xp Yp Zp Lp Mp Np]&#39; (vector with engine forces &amp; moments)

  Xa, Ya, Za: aerodynamic forces along aircraft&#39;s body-axes [N]
  La, Ma, Na: aerodynamic moments along aircraft&#39;s body-axes [Nm]

  Xp, Yp, Zp: propulsive forces along aircraft&#39;s body-axes [N]
  Lp, Mp, Np: propulsive moments along aircraft&#39;s body-axes [Nm]
</pre>
    <h3>
      <a name="Equations">Equations</a>
    </h3>
    The following expressions are used: 
<pre>
  X = CX*qdyn*S,   Y = CY*qdyn*S,   Z = CZ*qdyn*S
  L = Cl*qdyn*S*b, M = Cm*qdyn*S*c, N = Cn*qdyn*S*b
</pre>
    where: 
<pre>
  S        = wing area [m^2]
  c = cbar = mean aerodynamic chord [m]
  b        = wing span [m]
</pre>
    <p><i>CX</i>, <i>CY</i>, ... , <i>Cn</i> may equal <i>CXa</i>,
    ... <i>Cna</i>, <i>CXp</i>, ... <i>Cnp</i>, or any other
    sequence of force and moment coefficients which have been made
    dimensionless in the same way as the aerodynamic and propulsive forces and
    moments. </p>
    <h3>
      Parameters to be defined in the Matlab workspace
    </h3>
    <ul>
      <li>
        <i>GM1</i>: vector with some important geometrical properties of the
        &#39;Beaver&#39; aircraft, and the mass of the aircraft (which is
        assumed to be constant during the motions of interest). Here, the wing
        span <i>b</i>, mean aerodynamic chord <i>cbar</i>, and wing area
        <i>S</i> are extracted from <i>GM1</i>. <i>GM1</i> can be loaded into
        the workspace from file by running the utility <i><a href=
        "datload.htm">DATLOAD</a></i>. Run <i><a href=
        "modbuild.htm">MODBUILD</a></i> first if the datafile does not exist.
      </li>
    </ul>
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