Fabian wrote:
Currently , as far as I understand, JSBSim does not support
the buildup of the aerodynamic characteristics by taking the wing-body alone
and adding the tail contribution. This is essential for example in
investigating an aircraft behaviour during ice contaminated tailplane stall,
a "hot" subject nowadays.
For example, the total pitching moment would be:
CM_wing-body + CLtail * tail_volume.
Actually, JSBSim supports exactly that kind of thing. [You might want to
move this part of the discussion to the JSBSim list.] In JSBSim we use the
coefficient build-up method to define the forces and moments about each of
the axes. There is also the possibility of creating functions that calculate
whatever you want, which can then be applied to the coefficients as needed.
For example, multipliers into tables or other functions. You could use
DATCOM+ to calculate the wing/body effects, then add other effects as
needed, unless you already have data. For information on DATCOM+, see
www.holycows.net/datcom.
Of course, the aero model should then need to include the
downwash (Epsilon) at the tail (as a function of alpha, flaps, etc.) and
CLtail vs. alpha_tail.
My questions therefore are:
1. Is it possible to introduce Epsilon tables in the
aircraft properties file?
To my knowledge, nobody has tried this, yet. However, it is certainly
possible.
2. Is it possible to have an option to evaluate alpha_tail
(alpha_aircraft + horizontal_stab - Epsilon + dynamic components) whenever
an Epsilon table is present in the properties file? This would be essential
to calculate the tail lift and its contribution to the overall pitching
moment.
Yes. That's one of the reasons that we created the function capability. One
of our newsletters (see www.jsbsim.org) has information about defining
functions in the aerodynamics section of a JSBSim aircraft config file.
Also, there is this (somewhat formal) definition of JSBSim-ML:
http://jsbsim.sourceforge.net/JSBSim/JSBSim.xsd.html
Some information on the function definition can be found here:
http://jsbsim.sourceforge.net/wiki/index.php/User%27s_Manual#Configuration_F
iles
For more information, as on the JSBSim list!
Jon
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