>>>> Incidently, the FS variables are generally exact to five>>digits or more.>>>>Interesting>I was researched perfomance charts for some regional jet.>There was also CAS/Mach pairs for different altitudes and>temperatures. I noticed that when IAS from FS matches CAS on>chart, mach number little different, and vice versa. I tryed>convert IAS from FS to mach by formulas from>http://williams.best.vwh.net/avform.htm That URL appears to give the appropropriate TAS to CAS calculation. Many of the components are already calculated in my XML Jet Test. I know I do a value^3.5 calculation, which also appears at that site. In fact, I calcuate "Theta", "Theta_tot". Also the pair for Theta and Sigma in my Test Gauge. >IAS from FS, and converted mach pairs was exactly matched>pairs on chart. You really should start with TAS or Mach. Which are very accurate in FS. 'IAS' is only of interest to pilots, since that may be the only 'speed' indication they can see. IAS varies with Angle of Attack, Angle of Slip, at higher speeds compressability comes in. My commented aircraft.cfg (for pre FS9, Aired.ini Info) gives good values for the two IAS adjustment factors. I have had no need to use any but what I give for all jets. However, I have noted that IAS (appropriately adjusted) in FS jets starts deviating from what it should be around 330 kts. At 350 kts it is off by 5 kts or so. I probably used AFSD to see this. I've noted AFSD gives incorrect density and related things if the atmosphere is not ISA. While my XML calculations are based on L: Parameters that give correct density, etc. regardless of deviation from ISA pressures. I know I used the unit 'atmospheres' for 'pressure', since "1 atmosphere" would be at standard SL. The Theta and Delta factors are relative to 1.000 at SL. So, I take an XML L:Variable and divide by the SL value to get the current value.>Difference between mach readed from FS variable and calculated>mach about 0.015M when flying near 0.8M at FL370. Difference>is not so big but noticeable. Since FS Mach is virtually perfect, the error is in your 'IAS' or whatever you are basing Mach on. I think I mentioned I calculate TAS from FS Mach. Using FS TAS resulted in some problems when wind, abnormal attitude, etc was involved. I've attached a screen shot of an early Jet Test window to give an idea of what I've calculated and displayed. I may have fixed some errors in the calculations since.http://forums.avsim.net/user_files/107303.gifRon

Thank you, Ron

Thank you guys for all the replies to this thread. As a resumee I must - unfortunately - conclude that my intention to improve a few things on the default A/C cannot be achieved. But nevertheless following the discussion was very interesting.So let's take the lesson as I learned it:- Whether MSFS is regarded as a game or as a simulator is not really important. It's the way you look at it.- MSFS has the potential for quite accurate flight dynamics. The way it is handled by the developer team is in some cases a bit doubtful (I'm trying to be very careful in using these terms..;-) )- MS is not very helpful nor does it provide any significant help in developing flight dynamics or (especially in my case) altering flight guidance spec which are very A/C dependend. To be honest: They don't have to. It would just be very nice.......Nevertheless in my opinion MSFS still remains an excellent game/Flight Simulator and is by far worth it's price.Oskar

If you regard MSFS as a game, which is its classification, it makes its limitations much more palatable.I also think you may be somewhat misled buy what MS can or can not do. MS has many significant problems with their chosen way of modeling flight dynamics. XPlane and FlightGear are in far better position to model these accurately and more completely than MS will ever be (with out a complete rethink on their whole philosophy).MS has great scenery. Great visuals, wonderful worldwide terrain, well modeled airports and good looking AI. It has better sound, a better UI, significantly better weather, better view distance, better frame rate, and IMO a much greater level of emersion and believability.But, also IMO, it has a very weak flight dynamics model. It also has a very weak failures model and an even weaker damages model. (In this sense I much prefer X-Plane - though X-Planes other weaknesses are unforgivable and FlightGear is still alpha quality - thus my overall preference for MSFS) Given time I suspect MSFS will be everything we want it to be. But it may take a few more versions (esp. when you consider that while it may seem the simming community is large; in reality when compared to other game genres, it