[Flightgear-devel] Sopwith Camel model added

[Michael Selig]

I have just added a Sopwith Camel to the CVS. Not only does it
include the flight dynamics model, but also there's an external model
from A.F. Scrub! He has granted permission for us to use and release
these with FlightGear under the GNU GPL.

There's a readme file on the external model from A.F. Scrub in:
~/fgfsbase/Aircraft/sopwithCamel/Models/uiuc/sopwithCamel/

The flight model readme from ~/fgfsbase/Aircraft/UIUC/ is included below.
I've included a blurb about the initial motivation for this model as it relates some work for the Discovery Channel.

Regards,
Michael

======================================================
= Sopwith Camel F.1 =
= WWI Fighter =
= for FlightGear with LaRCsim and the UIUC Aeromodel =
= =
= Flight model by: =
= Michael Selig, et al. ([EMAIL PROTECTED]) =
= http://www.aae.uiuc.edu/m-selig/apasim.html =
= =
= External model by: =
= A.F.Scrub "Scrubby PC" ([EMAIL PROTECTED]) =
======================================================

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/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:

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

* Motivation: FGFS and the UIUC aero model were used to develop the
flight model of 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 ([EMAIL PROTECTED]) 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. 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 Aero/Astro 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)
mailto:m-selig@;uiuc.edu
http://www.uiuc.edu/ph/www/m-selig
http://www.uiuc.edu/ph/www/m-selig/faq.html (FAQ)
**************************************************


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