Curt wrote:

But Jon, this statement seems to run counter to your overall argument. Slats at least on many of the aircraft I've seen deploy linearly. In other words they are on some sort of rail mechanism and slide out away from the leading edge of the wing in a linear motion. They aren't attached with a hinge, there's no rotation at
all. So in this case representing linear motion with some arbitrary
angle seems a lot worse than representing angles with normalized values.

You're right - I had in my mind that we were discussing spoilers - not slats. Slats could be similar to landing gear, working in a 0 to 1 range.

In the case of YAsim, you may need to dig in and get a better understanding of it, but essentially, the way it works, it does not
need to know deflection angles.

Yes, I'm sure it's a pretty good approximation, but IMHO this is sloppy. In flight simulation you want to know deflection angles for any of a number of reasons. And, again, in some flight control systems you might have hardware or software limits placed on the aerosurface excursions. Does YASim arbitrarily choose the limits? Which limits? Where does the rendering system get the limits so it knows what the maximum travel means? The point is: if you take angular deflections from the FDM, you have all you need right there; angular measurements are used to do the drawing. If YASim specifies some range of travel that represents full deflection, then it can also easily pass you degrees deflection for an elevator, for instance.

As you pointed out earlier, elevator, rudder, aileron, flaps - those items are always or almost entirely always referenced in angular units - exactly the units needed for drawing, and native units that the FDM outputs. It seems to me that it would be polluting the property tree to provide these in normalized coordinates.

I think what I'd like to do for now is to put the normalization for these parameters outside of JSBSim and into the FGJSBSim interface code. But, I'll look at that some more before doing so.


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