    ======================================================
    = ASW 20                                             =
    = 15-meter class sailplane                           =
    = 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:                                 =
    = Roland Stuck (rstuck@evc.net)                      =
    ======================================================

    To run, try:

    fgfs --aircraft=asw20-v1-nl-uiuc

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

    asw20-v1-nl-uiuc-set.xml
    asw20/Models/uiuc/asw20-stuck/asw20-stuck-model.xml
    asw20/Models/uiuc/asw20-stuck/asw20.mdl
    asw20/Models/uiuc/asw20-stuck/asw20mp_.0af
    asw20/Models/uiuc/asw20-stuck/asw20mp_.1af
    asw20/Models/uiuc/asw20-stuck/asw20mp_.2af
    asw20/Models/uiuc/asw20-stuck/asw20mp_.3af
    asw20/Models/uiuc/asw20-stuck/asw20mp_.4af
    asw20/Models/uiuc/asw20-stuck/asw20mp_.5af
    asw20/Models/uiuc/asw20-stuck/asw20mp_.6af
    asw20/Models/uiuc/asw20-stuck/asw20mp_.7af
    asw20/Models/uiuc/asw20-stuck/asw20mp_.8af
    asw20/Models/uiuc/asw20-stuck/asw20mp_.9af
    asw20/Models/uiuc/asw20-stuck/asw20mp_.aaf
    asw20/Models/uiuc/asw20-stuck/asw20mp_.baf
    asw20/Models/uiuc/asw20-stuck/asw20mp_.caf
    asw20/Models/uiuc/asw20-stuck/asw20mp_.daf
    asw20/Models/uiuc/asw20-stuck/asw20mp_.eaf
    asw20/Sounds/uiuc/asw20-sound.xml
    UIUC/asw20-v1-nl/CDfa-01.dat
    UIUC/asw20-v1-nl/CLfa-01.dat
    UIUC/asw20-v1-nl/Cmfa-01.dat
    UIUC/asw20-v1-nl/Cmfade-01.dat
    UIUC/asw20-v1-nl/aircraft.dat

    These files above come with the FlightGear base package.

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

    Model description and updates:

    6/8/03: - Update:

    * Added spoilers using j/k keys to close/open spoilers.
      Added flaps    using [/] keys to raise/drop flaps

    * Set control deflections to be like ASW 27 for now.  Still looking
      for ASW 20 manual.

    12/25/02 - Update:

    * Elevator deflections up/down were swapped. Fixed w/ this one.

    * Add wind noises to sound file.

    11/8/2002 - First release: v1-nl

    * Roland Struck (rstuck@evc.net) has granted FlightGear permission to
      use and release the external model files with FlightGear under the
      GNU GPL.

    * This flight dynamics model simulates an ASW 20 15-meter sailplane.

    * A weights and balance was performed to arrive at an allowable
      c.g. location and from that data, mass moments of inertia were
      calculated.

    * Lift, drag and pitching moment data is modeled from -180 to +180
      deg.  In general, the aerodynamics are modeled using various sources
      too numerous to mention here.

    * Apparent mass effects are modeled.

    * The simulation starts on the ground.  To simulate being tow, the
      throttle can be used.  The "thrust" was tuned to simulate a
      reasonable line tension and max rate of climb while on tow.
      Alternatively, Ctrl-U can be used to jump up in 1000-ft increments.

    * Interesting flight characteristics to note:

      - When starting out, quickly change views to see the external
        aircraft.  The wings will start out level, and then one side will
        drop.  For whatever reason, the left wing drops first even though
        the data in the model is symmetrical.

      - Taking off requires careful control of the rudder and ailerons.
        Use rudder to line up with the runway and ailerons to level the
        wings.  It is easy to over correct (especially without a
        headwind), and the consequences should be reminiscent of being
        towed in a real sailplane.  [I am speaking from experience, being
        a sailplane pilot and having part owned a Pegasus (~ASW 19)].

      - The max lift-to-drag ratio is approx 42:1.  This means that from a
        height of 1 mile, the gliding distance is 42 miles.  This
        efficiency is most readily apparent when flying and landing.
        Adding spoilers is a high priority for the next update.

      - The long wings produce an over banking tendency when circling as
        would be done in thermals.  "Top aileron" is required to keep the
        wings from over-banking.  In addition extra rudder is then
        required to stay coordinated.

      - Tail slides and hammer heads appear to be quite realistic.  This
        is one bonus that comes from modeling key aerodynamic data from
        +-180 deg.

    * What is not yet simulated: water ballast, flaps, spoilers.

    * Drag due to rudder deflection, aileron deflection, and side slip are
      not yet added.  When these are added, slipping on landing will be
      more realistic.

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

    **************************************************
     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
    **************************************************