    ======================================================
    = Sopwith Camel F.1                                  =
    = WWI Fighter                                        =
    = 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:                                 =
    = A.F.Scrub "Scrubby PC" (af_scrubbypc@hotmail.com)  =
    ======================================================

    To run, try:

    fgfs --aircraft=sopwithCamel-v1-nl-uiuc

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

    sopwithCamel-v1-nl-uiuc-set.xml
    sopwithCamel/Models/uiuc/sopwithCamel/cambelg0.bmp
    sopwithCamel/Models/uiuc/sopwithCamel/cambelg1.bmp
    sopwithCamel/Models/uiuc/sopwithCamel/cambelg2.bmp
    sopwithCamel/Models/uiuc/sopwithCamel/cambelg3.bmp
    sopwithCamel/Models/uiuc/sopwithCamel/cambelg4.bmp
    sopwithCamel/Models/uiuc/sopwithCamel/cambelg5.bmp
    sopwithCamel/Models/uiuc/sopwithCamel/cambelg6.bmp
    sopwithCamel/Models/uiuc/sopwithCamel/cambelg7.bmp
    sopwithCamel/Models/uiuc/sopwithCamel/cambelg8.bmp
    sopwithCamel/Models/uiuc/sopwithCamel/cambelg9.bmp
    sopwithCamel/Models/uiuc/sopwithCamel/Sop-panel.bmp
    sopwithCamel/Models/uiuc/sopwithCamel/camel.txt
    sopwithCamel/Models/uiuc/sopwithCamel/cambelg.mdl
    sopwithCamel/Models/uiuc/sopwithCamel/sopwithCamel-model.xml
    sopwithCamel/Models/uiuc/sopwithCamel/README.TXT
    sopwithCamel/Sounds/uiuc/sopwithCamel-sound.xml
    UIUC/sopwithCamel-v1-nl/aircraft.dat
    UIUC/sopwithCamel-v1-nl/CDfa-06.dat
    UIUC/sopwithCamel-v1-nl/CLfa-06.dat
    UIUC/sopwithCamel-v1-nl/Cmfa-06.dat
    UIUC/sopwithCamel-v1-nl/Cmfade-03.dat
    UIUC/sopwithCamel-v1-nl/README.sopwithCamel.html

    These files above come with the FlightGear base package.

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

    Model description and updates:

    11/10/2002 - Notes below added

    * The Sopwith Camel did not have brakes.  Application of brakes in
      FGFS will cause the aircraft to promptly nose over.  (I have added a
      fake contact point so that the aircraft does not completely tip
      over.)  The c.g. of the aircraft sits almost directly above the
      wheel contact point.  There is a reason for this.  The aft fuselage
      and tail were designed to be very light.  Thus, the tail could not
      support much load, so the weight of the aircraft largely rests on
      the main wheels, which again requires the c.g. to be almost directly
      above the wheels.

    * WWI aircraft engines did not have a conventional throttle (at least
      most did not).  The engines were either on or off/idle using a
      "blip-throttle".  So it is not realistic to fly with a variable
      throttle, which the current model allows.

    * To modelers, I can provide a graphic showing the c.g. location.

    * To those having specific knowledge of the Sopwith Camel, I am
      interested in obtaining the following data:

      [] Wing airfoil section

      [] RPM when the throttle is blipped.  I am currently using 300 RPM.
         The current aircraft uses a 150-hp Bentley B.R.1 engine, which is
         what Capt Brown was flying on the day when he claimed to kill the
         Baron von Richthofen (The Red Baron).

      [] Engine mass characteristics on a component-by-component basis.
         This information will help me refine the polar moment of inertia
         that drives the gyroscopic forces.

      [] On a related note, the mass of the propeller which also figures
         into the gyroscopic forces.

    11/9/2002 - First release: v1-nl

    * Motivation: FGFS and the UIUC aero model were used to develop flight
      models for both the Sopwith Camel and Fokker Dr.1 Triplane.  These
      models were then used in another simulation with a collaborator,
      Brian Fuesz.  In that simulation, guns, terrain, villages, multiple
      planes, etc were added to simulate the last flight of the Red Baron.
      This work was filmed for the Discovery Channel show "Unsolved
      History: The Death of the Red Baron" scheduled to first air Dec 18,
      2002.

    * A.F. Scrub (af_scrubbypc@hotmail.com) has granted FlightGear
      permission to use and release the external model files with FlightGear
      under the GNU GPL.

    * 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.

    * Apparent mass effects are modeled.

    * Gyroscopic forces caused by engine rotation and aircraft rotations
      are modeled.  For an animation of how a WWI-type rotary engine works,
      go here:http://www.keveney.com/gnome.html
      An example of gyroscopic forces, are those forces produced when one
      tries to rotate by hand a spinning bicycle wheel.

    * Spin aerodynamics are not yet modeled.

    * The simulation starts on the ground.  Throttle up to take off or
      alternatively, use Ctrl-U to jump up in 1000-ft increments.

    * Interesting flight characteristics to note:

      - The Sopwith Camel was considered a "beast" to fly.  It killed 385
        pilots while they were in training (non-combat).  In combat, 415
        of the surviving pilots were killed while flying the Sopwith
        Camel.  Approximately 5000 Sopwith Camels were built, and it is
        believed that collectively 1294 enemy aircraft were destroyed.

      - In large part, the challenges to flying the Sopwith Camel involve
        the large gyroscopic forces from the rotating engine (which
        rotated clockwise when viewed from the cockpit).  Pulling nose up
        causes the aircraft to yaw to the right, yaw right and it noses
        down, nose down and it yaws left, yaw left and it noses up.  Thus
        whatever the direction the nose goes, the airplane slews to the
        right of that path.  This was particularly dangerous for
        right-hand turns if not properly managed.  The initial roll to the
        right takes place without any surprise.  But after having banked,
        pulling up elevator to turn causes the nose to "slew" to the right
        of the intended direction.  In this case, it leads to the nose
        pointing down, which in turn leads to a tail skid.  This skid
        could then easily precipitate into a spin.  Should that happen,
        the gyroscopic forces continue to do their work.  If control is
        recovered, during the pull out it is very easy to fly on the back
        side of the power curve.  If that happens, the pullout is very
        slow, and it is easy to auger-in.

      - As mentioned in the current sim, spin aerodynamics are not
        modeled, so the scenario just described will not happen.  However,
        the skidding is most apparent.  And it is quite easy to fly into
        the backside of the power curve from any flight attitude (there is
        ample "elevator power").  Keeping the speed up in general is one
        way to avoid this regime.

      - Rudder authority on the Sopwith Camel was inadequate, and it only
        increased the chances of spinning in.  Surely, the designers were
        aware of this fact, but a larger rudder would have led to more
        weight aft not only because of the shear mass of the tail, but
        also because of the larger structure required to support the
        larger airloads.  This solution surely countered the design
        philosophy of trying to put as much weight as possible between the
        pilot and engine, all in an attempted to increase maneuverability
        by keeping the moments of inertia as small as possible.

      - On takeoff, when the tail raises (nose down rotation) note the
        strong yaw to the left attributable to the gyroscopic forces.

      - In general, to stay coordinated in turns requires generous use of
        the rudder.

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

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