At 10:49 PM 1/4/2002 -0600, Jon S. Berndt wrote: >This assumes that MS is doing things correctly and/or the way things >should be done. This is an invalid assumption. This is one of the reasons >I, personally, wanted to begin writing an FDM. >
A heavy assumption indeed. The MSFS flight model is crude at the logic level, and no amount of knob-twisting in the .air files can make it work right. Uncoordinated flight is a good example. It seems to work like this: heading gets incremented based on a coordinated turn at the existing airspeed and bank angle. Then the rudder position is compared to a "correct" position, and the nose is yawed off the flight path by an angle proportional to the error. The "correct" position seems to be a pulse of size determined by the roll rate -- in other words, a canned sequence. Lateral lift component is not modeled -- i.e., no matter how much uncoordinated rudder is applied, the airplane continues along the flight path determined by the bank angle history. It is impossible to make a skidding turn (which includes fine heading adjustments with rudder on an ILS) or to do a slip. Applying rudder without aileron pressure will turn the airplane, but only because another canned sequence applies a bank input; this bank actually controls the turn. Worse yet, as far as I can tell, variation of induced drag with angle of attack isn't modeled. And the seaplane model is beyond belief. An airplane on the water sits in a fixed position and heading regardless of wind and power setting until the throttle setting exceeds a threshold; then it starts to accelerate. Only then can it be turned. In other words, all they did was to take the ground model and add a gentle bobbing motion in the vertical axis. On the plus side, there are some lovely exterior graphics and some pretty good panels. But I don't think any part of the MSFS models could be used to determine flight performance of the aircraft. rj _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
