On Thursday 25 Jun 2009, Maik Justus wrote: > Hello Olivier, > > Olivier Faivre schrieb am 25.06.2009 20:52: > > Hello guys, > > ... > > Actually, the wing is done with only one piece, 7° dihedral, no > > twist. Can I use the "mstab" command to specify the outer wing > > and the regular "wing" command for the inner one ? > > yes > > > In the readme file, I read this for mstab : these surfaces are > > not involved with the solver computation these surfaces are not > > involved with the solver computation... > > > > I'm not sure to well understand. > > if you define a yasim FDM you have to define two configurations > with different airspeed, typ. cruise and approach. Yasim modifies > lift and drag factors and the incidence of the wing to meet these > configurations. Therefore the incidence of a wing will be > modified by the yasim solver (only once - when the model is > loaded) while the incidence of a mstab is unchanged.
I just thought I'd point out that the YASim solver sets the incidence for the <hstab> element, not the <wing> element. Thus, you can specify the incidence for the <wing>, but not for the <hstab>. There is also an INCIDENCE control-axis in YASim, which should allow the <wing> element incidence to be changed in flight and I think the F-8E, which is shown on the FG aircraft download web-page, may actually use this. However, when I've tried using the INCIDENCE control-axis with <vstab> or <mstab> elements, to simulate all-moving/slab tailfins/rudders (as in the BAC-TSR2) or all-moving canards (as in the SU-37) it has had no aerodynamic affect at all. YASim does indeed generate drag factors for <wing>, <vstab> and <mstab> elements, but it is possible to modify the the AoA related drag forces by including suitable <idrag> elements . This seems to work well when you're trying to simulate all-moving tailplanes, for example, if you specify a very low <idrag> factor for the <hstab> element. I also experimented with using <mstabs> to more accurately model the correct shape of wings when developing the Canberra-B(I)8 YASim config but found that the solver does indeed ignore the <mstab> elements when working out its stuff. While I could get it to solve, the effect was that of just having the very short inner wing panels. The <vstab> and <mstab> elements do have directional effects however, and the control-surface sub-elements, such as <flapn> and <spoiler> will also have an effect. For the main lifting surface then, using a full-span <wing> element will give more accurate results than a combination of <wing> and <mstab> elements because the <mstab> elements will be ignored. Although this may seem less than ideal, it's possible to fine-tune the single <wing> element to get very close to the real world characteristics, and certainly closer than you could get with a <wing> and <mstab> combination. LeeE ------------------------------------------------------------------------------ _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
