    ======================================================
    = Generic Hang Glider                                =
    = for FlightGear with LaRCsim and the UIUC Aeromodel =
    =                                                    =
    = Flight model by:                                   =
    = Michael Selig, et al. (m-selig@uiuc.edu)           =
    = http://www.aae.uiuc.edu/m-selig/apasim.html     =
    =                                                    =
    = External model by:                                 =
    = Captain Slug (captainslg@aol.com)                  =
    ======================================================

    To run, try:

    fgfs --aircraft=airwaveXtreme150-v1-nl-uiuc

    Files and directory structure required in $FG_ROOT/Aircraft/ to fly the
    model:

    airwaveXtreme150-v1-nl-uiuc-set.xml
    airwaveXtreme150/Sounds/uiuc/airwaveXtreme150-sound.xml
    UIUC/airwaveXtreme150-v1-nl/aircraft.dat
    UIUC/airwaveXtreme150-v1-nl/CDfade.dat
    UIUC/airwaveXtreme150-v1-nl/CLfade.dat
    UIUC/airwaveXtreme150-v1-nl/Cmfade.dat
    UIUC/airwaveXtreme150-v1-nl/README.airwaveXtreme150.html
    airwaveXtreme150/Models/uiuc/hgldr-cs/hgldr_cs.0af
    airwaveXtreme150/Models/uiuc/hgldr-cs/hgldr_cs.1af
    airwaveXtreme150/Models/uiuc/hgldr-cs/hgldr_cs.mdl
    airwaveXtreme150/Models/uiuc/hgldr-cs/hgldr-cs-model.xml

    These files above come with the FlightGear base package.

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Model description and updates:

    11/8/2002 - External model files added.

    * Permission granted to use and release these with FlightGear under
      the GNU GPL.  Thanks go to Captain Slug (captainslg@aol.com)!

    5/25/2002 - First release: v1-nl

    * Despite its namesake, this is not intended to be a model of the
      Airwave Xtreme hang glider.  However, this hang glider has relatively
      high performance with a max L/D of approximately 12, which is in
      line with the Airwave Xtreme 150.

    * Lift, drag and pitching moment is modeled from -180 to +180 deg.

    * In longitudinal flight, moving the control bar fore and aft does two
      things simultaneously.  It changes the c.g. of the hang glider as well
      as the angle of attack of the wing.  This changes the lift, drag and
      moment about the c.g.  These effects are properly modeled.  The
      c.g. shift is not modeled for lateral directional flight, however.
      Instead a typical aileron is modeled for roll control.  Thus joystick
      position controls the fore/aft c.g. for pitch and "aileron" deflection
      for roll.

    * Apparent mass effects are modeled, and this together w/ the c.g. shift
      both produce the characteristics hang glider landing dynamics -- big
      flares.

    * Full aft c.g. (aft joystick) will put the hang glider in a vertical
      stable descent.  On average, the pitching moment characteristics of a
      hang glider lead to stable flight at near 90 deg angle of attack
      (vertical descent).  In real life unsteady vortex shedding would
      prevent stable flight in this regime.  This unsteadiness might be
      modeled in later versions.

    * The aerodynamics are modeled after experimental data taken by
      Ormiston, R.A., "Wing Tunnel Tests of Four Flexible Wing Ultralight
      Gliders," NASA CP 2085, Part II, March 1979, pp 557-589.  These
      gliders are "vintage" hang gliders with more or less poor performance
      relative to modern hang gliders.  To better model current day hang
      gliders, some adjustments were made to the pitching moment and drag
      polar.  With the adjustment to the drag polar, the maximum L/D is now
      approximate 12.  Pitching moment data is discussed more below.

    * Because a hang glider controls pitch with c.g. shift, the pitching
      moment curves are anything but linear.  This produces interesting
      aerodynamic control effects.  Most notably, at low speeds, it is
      relatively easy to pitch up the glider; whereas, at high speeds, the
      pitch up is slower.  Low speeds are experienced during landing, in
      particular the exaggerated flare.  High speeds can be had in a
      vertical dive.  Some adjustments were made to the experimental
      pitching moment data to more closely model the better handling of
      current hang gliders.  (If I can find a 3D model of an older
      lower-performance hang glider (1970 vintage), I will put back in the
      scary characteristics that led to many early hang glider accidents.)

    * The hang glider simulation starts on the ground, and in real life
      there is no engine.  Because this is not real life, one of two things
      can be done to reach altitude.  Ctrl-U can be used to jump up in
      1000-ft increments.  Alternatively, an engine is included; add
      throttle and the hang glider will climb.

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    **************************************************
     Prof. Michael S. Selig
     Dept. of Aerospace Engineering
     University of Illinois at Urbana-Champaign
     306 Talbot Laboratory
     104 South Wright Street
     Urbana, IL 61801-2935
     (217) 244-5757 (o), (509) 691-1373 (fax)
     m-selig@uiuc.edu
     http://www.aae.uiuc.edu/m-selig
    **************************************************