📄 flpath.htm
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<TITLE>FDC help: Flpath</TITLE>
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<H2>Subsystem <I><FONT FACE="Arial","Helvetica","Sans Serif">Flpath</FONT></I></H2>
<I><FONT SIZE=2 FACE="Arial","Helvetica","Sans Serif">Flpath</FONT></I> is a masked S<SMALL>IMULINK</SMALL> subsystem, which computes some flight-path related parameters. Since the outputvariables from <I><FONT SIZE=2 FACE="Arial","Helvetica","Sans Serif">Flpath</FONT></I> are not needed for solving the equations of motion themselves, this block has been included in the subsystem <I><FONT SIZE=2 FACE="Arial","Helvetica","Sans Serif"><A HREF="moreouts.htm">Additional Outputs</A></FONT></I>. It is therefore possible to delete the block <I><FONT SIZE=2 FACE="Arial","Helvetica","Sans Serif">Flpath</FONT></I> from the system <I><FONT SIZE=2 FACE="Arial","Helvetica","Sans Serif"><A HREF="beaver.htm">Beaver</A></FONT></I>, but in that case the connections to the <I><FONT SIZE=2 FACE="Arial","Helvetica","Sans Serif">Outport</FONT></I> and <I><FONT SIZE=2 FACE="Arial","Helvetica","Sans Serif">To Workspace</FONT></I> blocks need to be checked.
<H3>Inputvectors: <I>x</I> and <I>xdot</I></H3>
<PRE> x = [V alpha beta p q r psi theta phi xe ye H]' (states)
xdot = dx'/dt (time derivative of state vector)
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] }
</PRE>
The variables which are not actually needed by <I><FONT SIZE=2 FACE="Arial","Helvetica","Sans Serif">Flpath</FONT></I> have been displayed between accolades. Of the vector <I>xdot</I>, the time derivatives of <I>V</I> and <I>H</I> are used.
<H3>Outputvector: <I>yfp</I></H3>
<PRE> 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]
</PRE>
<H3>Parameters to be defined the M<SMALL>ATLAB</SMALL> Workspace</H3>
The block <I><FONT SIZE=2 FACE="Arial","Helvetica","Sans Serif">Flpath</FONT></I> needs the initial value of the angle of attack to compute the bank angle. This initial (trim) value of alpha is read from the initial state vector <I>xinco</I>, which must be defined in the M<SMALL>ATLAB</SMALL> workspace before starting simulations. The M<SMALL>ATLAB</SMALL> program <I><FONT SIZE=2 FACE="Arial","Helvetica","Sans Serif"><A HREF="actrim.htm">ACTRIM</A></FONT></I> can be used to determine steady-state initial flight conditions; the utility <I><FONT SIZE=2 FACE="Arial","Helvetica","Sans Serif"><A HREF="incoload.htm">INCOLOAD</A></FONT></I> can be used to load such conditions from file.
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