Ok, here are a couple of thoughts on improving the elevator model; as always comments and suggestions are welcome, flames will be ignored
@ line 220 or so of FGAerodynamics add: alphat = alpha + tailincidence - downwash; // alpha fro the tail for now we'll assume no flying tails just a normal hinged elevator, so the incidence is fixed and specified in the aircraft xml file. To calculate the downwash we use the following formula downwash = 2 * CL(wing) / (pi * AR) where AR is the aspect ratio of (cbar*cbar)/Sw, but cbar is actually a variable dependent on the wing/flap configuration; so we need to recalculate cbar whenever the configuration changes and, at some point, we'll need to consider any delta cbar as a time dependent variable based on flap extension/retraction rates. Obtaining CL and pi is trivial, so the task at hand is the best way to calculate the aspect ratio - something that only has to happen when the wing configuration changes. So once we have the alpha at the tail and assuming a trim tab set to some value the stick free elevator (aka floating) becomes elev_float = - ((b1*alphat + b3*trim)/b2*elevator) * alphat where b1 = (partial) Ch with respect to (partial) alphat and b2 = (partial) Ch with respect to (partial) elevator and b3 = partial Ch with respect to (partial) trim All that remains is to calculate the elevator balance position where Cm = 0; i.e., steady state flight aka a trimmed aircraft or elev_float = elev_balance I'll stop here for now. The next set of calcs would be to determine the control force gradient to apply to the stick as it is moved from the neutral (or zero stick force location). Regards John ------------------------------------------------------------------------------ Create and publish websites with WebMatrix Use the most popular FREE web apps or write code yourself; WebMatrix provides all the features you need to develop and publish your website. http://p.sf.net/sfu/ms-webmatrix-sf _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
