Does anybody has an idea about the differences and their impacts between the historical flight model and the Modern flight model we can choose in the options menu ?
Thanks in advance.
I think it refers to the implementation of the flight model in the sim. “Historically”, they used lookup tables or some such to calculate the forces acting on the airplane. Whereas the “modern” implementation uses something more akin to the “blade element theory” in x-plane. Take all that with a grain of salt though 
. The newer implementation should behave better with respect to stalls and the like.
One is based on how FSX worked the other is the newer system. What those actual differences are I couldn’t tell you. I know that with some of the older planes getting ported over they tend to work better with the old flight model.
I am going to assume they put the option in there for people that were used to or liked the old flight model better. Giving them the option to switch back to it if they wanted. Just like adding all the assists and making it easier to use. I think they kind of went out of their way to make it more rounded so more people could enjoy it. Not just hardcore simmers that want ultra realism. Unfortunately it seems they kind of dropped the ball on some of the stuff like navigation and system controls which is really bothering some people that wanted the realism. Sort of like maybe they were more concerned with new people and not more experience simmers.
Not sure what their reasoning was behind it, but I guess it worked for them. It sold like crazy from the looks of it lol.
The legacy model uses stability and control derivatives and coefficient tables for lift and moment curves throughout the AoA range. The problem with that system is that the vast majority of people don’t understand it and it’s difficult to develop with that system. The modern system, while I’m not totally familiar yet, should be using the geometry of the airplane, which is much easier for the user to get data, either off a drawing or from some publication like Jane’s, etc. Back with FSX, Microsoft had started to move things from the .air file into the configuration file and had started making it so that some of the geometry inputs had an effect on the flight model. But, because not all of them did, developers got lazy and just didn’t bother to put in realistic values, knowing that they had no effect. That is the reason that they don’t work well with the modern flight model when ported over. There’s a lot to be learned over the next while and I suspect even the modern flight model is not final yet.
FYI - this question was posed in the thread below, and sparked a discussion about the modern flight model. In short, the legacy model is based on look-up tables of aerodynamic coefficients and stability derivatives calculated by external means. In the modern model, a lot of the aerodynamics is calculated in real-time based on the geometry.
https://forums.flightsimulator.com/t/modern-flight-model/232844
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