M7, I started looking at flight modelling when I was mod leader for Target4Today at Targetware and what I saw was that a Hurricane, a Be109, a Spit, a Fw190 and all their variants should have a relationship to each other.. they were not designed in isolation but in response to a particular flight characteristic of another. But this relationship didn't exist within Targetware as each plane was created by an individual for the game in apparent isolation and brought into the sim with the declaration 'this plane hits all the numbers'......
So simply put if all planes brought into a sim 'hit all the numbers'.... the relationships don't matter a jot as all planes are perfect and behave as they should.... But here's the rub.
Flight Modelling is often described as being a bit of a 'black art', what this translates too is that it's an exercise in compromise. Most jsbsim flight models created only have data for inbetween the plus minus angle of attack stall points with no attempt to understand what's happening once a wing stalls, so no spins or effects associated with climb stalls, high speed stalls
http://flighttraining.aopa.org/students/maneuvers/skills/stalls.html.
Then there's the issue of what's important to a flight model, and you'll hear alot about determining a planes co-efficients of lift and drag and there are programs out there that'll do that and yet here again you'll find only for certain configuations (bi-planes. no way) and only within the safe operating envelope... and only for a wing made up of a single airfoil and incidence... There must be a plane whose wing uses a single airfoil and incidence but apart from a paper one, I don't know what it is. So from a flight modelling co-efficients stand point you're compromised from the get go, before you even start adding your own compromises into the mix.
Then there's a Mass Ballance, moments of inertia and CoG position of a plane and getting the data for this, and there are genuinely very few sources for this, so it's invariably a made up set of of numbers with no relationship to the materials and construction techniques used in the design and build of the plane.. These are important values and JSBsim gives you the opportunity to use them if you have them (you can't omit them) but determining them for say a 1915 bi-plane or for finding the actual values for an f18 or f22 , good luck.
And now I come into the fray..... I simply refuse to compromise, and I never use a 'magic number' to make my planes 'hit the numbers'.. So I'm totally at odds with the whole flight model building community as exists in Flightgear and JSBsim. And as such have had the tendency to ruffle a few feathers to say the least.
I've come here to Outerra because you guys are at the beginning of a flight sim creation. You have no baggage, no thousands of hours invested and all the politics that go with it... of "that's the way it's done here"... You have no Guru's who's opinions are above questioning and you're as equally open to combat as non-combat aircraft. There are simply no walls that need tearing down before we can start doing something correctly, we simply start doing it correctly.
M7, the answer to you question is so complicated that we don't just need a new thread for it.....but a new flight modelling forum....
So Outerra developers, could we please have a new child flight modelling forum ?
Regards
Simon