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= 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) =
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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.
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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.
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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
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