And since FS most of the time assumes linear relations in algorithms,the model will only be ballpark numbers in most cases.

Actually, the table based flight engine of MSFS allows the designer to hit the required numbers dead on. It's a real advantage when you need to replicate airspeeds with gear and flap deployments such as you would with an IFR approach over the markers. It is a fact, that you must take the numbers from a "known flying airplane".........to put into the MSFS sim. Thats the only real advantage I see in X-Plane. You can design, fly, and get an idea of what it will do............to a degree. I don't know about the X-Plane side, when it comes to added programming to hit the numbers, as I'm only familiar with the beta tests for numerous MSFS models. Yet I do know, that aircraft straight out of X-Plane Plane Maker seldom hit the numbers, and are "ballpark" at best. L.Adamson

Actually, the table based flight engine of MSFS allows the designer to hit the required numbers dead on. It's a real advantage when you need to replicate airspeeds with gear and flap deployments such as you would with an IFR approach over the markers. It is a fact, that you must take the numbers from a "known flying airplane".........to put into the MSFS sim. Thats the only real advantage I see in X-Plane. You can design, fly, and get an idea of what it will do............to a degree. I don't know about the X-Plane side, when it comes to added programming to hit the numbers, as I'm only familiar with the beta tests for numerous MSFS models. Yet I do know, that aircraft straight out of X-Plane Plane Maker seldom hit the numbers, and are "ballpark" at best. L.Adamson

Larry,I'm sorry to say, when it comes to flight models in FSX and X Plane, I would advise against having a detailed discussion or debate with Morten. You will lose.He knows as much about flight models as Bill Gates does about Microsoft.

Thanks Goran, but I don't know too much about the FS model otherthan what I can read. Don't have much practical experience with it.Below is by Michael K. Zyskowski, Microsoft. It's a few years old (FS2004)and updates have probably been made but I assume the general idea still applys.MSFS Flightmodel docHigh Alpha/Beta Table Look-upsAlthough most of the terms defined for an aircraft flight model’s stability and control characteristics are of the linear non-dimensional form, two-dimensional tables are also used to capture the non-linear behavior of aircraft at HIGHER angles of attack and sideslip. The CLα and CMα values used in the SimEngine are obtained through linear interpolation of a table for a given angle of attack, and are the only exceptions to this rule. All the other non-dimensional aerodynamic coefficients are non-linearized through the use of tables generated specifically for each coefficient. An interpolation routine is used to find the non-linear effect of a given coefficient, which is simply a scalar value multiplied by the base linear-form of the coefficient, to obtain the correct behavior in the non-linear range.In essence, we incorporate both a linear non- dimensional coefficient methodology for simplicity with a table look-up methodology to capture the non- linear effects of aircraft behavior at extreme incidence angles.In other words, they only use lookup tables at extreme angles (apart from Cl & Cm). Otherwise they use linear equations for simplicity!Lookup tables offcourse also have holes in them and will also need to do LINEAR interpolations!The result will look something like this (attachment). Fat red line is FS Cd curve, thin one is XP.Now add to this FS extremely simplified airfoil model and the end result is highly questionable froman engineering point of view.While we are looking at this document it also reveals a MAJOR misunderstanding about howground effect works;However, we utilize the ratio of height AGL to aircraft wing span to simulate the additional lift experienced in ground effect.Ouch...Thats not only way simplified, it is completely wrong!Basically they have mixed up SPAN dominated ground effect with CHORD dominatedground effect. Lift increase is a factor of CHORD above AGL, not span!It could be they had no choice since the FS wing is not devided into sections and chordslike XP is.So this means that all acft in FS with the same SPAN will experience the SAME lift increase in ground effect.A glider with the same span as a Concorde will have the same lift increase in FS.. Doh.. . Even high wing aircraft which in real usually never enters chord dominated ground effectwill get a lift increase Bummer..!Also no drag reduction or downwash pitchdown.Don't get me wrong, I'm possibly one of whom that has documented most errors in XP's flightmodelover the years, and I can tell you it is not perfect either. It however gets better every day and in myopinion is superior FS. It however also boils down to the designers and the top FS planes are asgood as the best XP acft today. This however will soon change... ;)M

Thanks Goran, but I don't know too much about the FS model otherthan what I can read. Don't have much practical experience with it.Below is by Michael K. Zyskowski, Microsoft. It's a few years old (FS2004)and updates have probably been made but I assume the general idea still applys.MSFS Flightmodel docHigh Alpha/Beta Table Look-upsAlthough most of the terms defined for an aircraft flight model’s stability and control characteristics are of the linear non-dimensional form, two-dimensional tables are also used to capture the non-linear behavior of aircraft at HIGHER angles of attack and sideslip. The CLα and CMα values used in the SimEngine are obtained through linear interpolation of a table for a given angle of attack, and are the only exceptions to this rule. All the other non-dimensional aerodynamic coefficients are non-linearized through the use of tables generated specifically for each coefficient. An interpolation routine is used to find the non-linear effect of a given coefficient, which is simply a scalar value multiplied by the base linear-form of the coefficient, to obtain the correct behavior in the non-linear range.In essence, we incorporate both a linear non- dimensional coefficient methodology for simplicity with a table look-up methodology to capture the non- linear effects of aircraft behavior at extreme incidence angles.In other words, they only use lookup tables at extreme angles (apart from Cl & Cm). Otherwise they use linear equations for simplicity!Lookup tables offcourse also have holes in them and will also need to do LINEAR interpolations!The result will look something like this (attachment). Fat red line is FS Cd curve, thin one is XP.Now add to this FS extremely simplified airfoil model and the end result is highly questionable froman engineering point of view.While we are looking at this document it also reveals a MAJOR misunderstanding about howground effect works;However, we utilize the ratio of height AGL to aircraft wing span to simulate the additional lift experienced in ground effect.Ouch...Thats not only way simplified, it is completely wrong!Basically they have mixed up SPAN dominated ground effect with CHORD dominatedground effect. Lift increase is a factor of CHORD above AGL, not span!It could be they had no choice since the FS wing is not devided into sections and chordslike XP is.So this means that all acft in FS with the same SPAN will experience the SAME lift increase in ground effect.A glider with the same span as a Concorde will have the same lift increase in FS.. Doh.. . Even high wing aircraft which in real usually never enters chord dominated ground effectwill get a lift increase Bummer..!Also no drag reduction or downwash pitchdown.

For starters,........ whether it's induced drag from span, or increased lift from chord, the (ground) effect is adjustable. I highly doubt that a model straight out of X-Planes "Plane maker" would be capable of being used to determine actual ground effect & wing tip vortices's for a real aircraft. The shape of the bottom of the wing, has much to do with it too. For instance, my RV6A with a semi-symmetrical wing, wide chord, and low aspect ratio.......seems to have no ground effect at all, when I land. It will fall right through the flare if I don't arrest the descent at the perfect moment before airspeed bleeds to quickly. Much has to do with the constant speed prop too, as it acts like a big air brake. There is no sense of a "cushion". In fact, I have yet to find a sim, that replicates the effects of a C/S prop, as much as I'd like. And speaking of RV's..........the models that come with X-Plane are completely wrong when it comes to the use of flaps. They pitch up & balloon like a high wing Cessna, where real RV's pitch down, and descent slightly, if you don't use a slight amount of back pressure. I don't know if those RV examples are straight out of plane maker or not, but they need a lot more refinement in several areas.As to the basics of the MSFS flight model, designers such as Rob Young (RealAir ) and Bernt Stolle, as well as numerous others........have taken the flight model well beyond the original designs. Therefor, just as with X-Plane........it's not too accurate to compare basics out of the box. But.........I'm all for X-Plane 10 being the greatest piece of software, next to the real thing. I can always jump ship.........so to speak. We'll just have to see! :( P.S. --- The short low aspect wings of my RV, and even the longer wing of the RV9 emit wing tip vortices's that border on a Boeing 757. It's enough to flip a following aircraft almost 90 degrees. First sim to duplicate that........wins! L.Adamson

Larry,I'm sorry to say, when it comes to flight models in FSX and X Plane, I would advise against having a detailed discussion or debate with Morten. You will lose.He knows as much about flight models as Bill Gates does about Microsoft.

I base my thoughts on real flight verus what I sense in a sim. While I have no experience in the cockpit of a jet airliner, I'm quite diversified in small planes, ranging from spam cans (Cessna, Piper), to experimentals, the Pitts, Marchetti, Stearman, and as a backseat observer in a P-51D.L.Adamson

For starters,........ whether it's induced drag from span, or increased lift from chord, the (ground) effect is adjustable. I highly doubt that a model straight out of X-Planes "Plane maker" would be capable of being used to determine actual ground effect & wing tip vortices's for a real aircraft.

Not sure what you are trying to say. Trying to "adjust" FS ground effect (GE) as described above by MS is impossible because its all wrong! Cant be done! You would need to code a completely new custom ground effect.We have been adjusting XP's ground effect for years, it models all effects on all types of wings and GE types.XP's model is lightyears ahead of FS here. But perfect - probably not.

The shape of the bottom of the wing, has much to do with it too. For instance, my RV6A with a semi-symmetrical wing, wide chord, and low aspect ratio.......seems to have no ground effect at all, when I land. It will fall right through the flare if I don't arrest the descent at the perfect moment before airspeed bleeds to quickly

Lift increase is due to RAM pressure buildup and airfoil shape has little to do with it - you usually land with flap anyway.What matters is GEAR LEG LENGTH, CHORD length and DIHEDRAL and FLAP. The RV6A will hardly notice a lift increase and get a late drag reduction due to short span. As you can see on photo's wing altitude is at about 1/2 chord whenon the ground. Compared to e.g. an airliner which is at maybe 1/8 th chord altitude on the ground and also increase chord with flap.On e.g. a B777 the outer parts of the wing will never enter Chord (lift) ground effect due to dihedral and taper. XP models this very well.Checked not too long ago.

. Much has to do with the constant speed prop too, as it acts like a big air brake

. True

the models that come with X-Plane are completely wrong when it comes to the use of flaps. They pitch up & balloon like a high wing Cessna, where real RV's pitch down,

Could be, but thats a designer mistake, can easy be fixed in PlaneMaker.(on the new 737 we are building, like in real we model the aircraft pitches up on some flap settings and down on others, but that requires a plugin)

As to the basics of the MSFS flight model, designers such as Rob Young (RealAir ) and Bernt Stolle, as well as numerous others........have taken the flight model well beyond the original designs. Therefor, just as with X-Plane........it's not too accurate to compare basics out of the box.

I'm sure Bernt and others have done a great job. Bernt in the past did some testflying on some of XPFW older aircraft for us.A lot has happened since then.

P.S. --- The short low aspect wings of my RV, and even the longer wing of the RV9 emit wing tip vortices's that border on a Boeing 757. It's enough to flip a following aircraft almost 90 degrees. First sim to duplicate that........wins!

Thought XP already modeled wake turbulence, no idea how realistic is tho, never tried it :( M

Lift increase is due to RAM pressure buildup and airfoil shape has little to do with it - you usually land with flap anyway.

This article claims that it does (airfoil shape). But who knows, as we still argue about "what causes lift".http://www.se-technology.com/wig/html/main.php?open=aeroL.Adamson

Hi Morten,As a newbie with a passing interest in the aerodynamics of GA aircraft.....Do you know if there is an "Idiots Guide To Planemaker" anywhere?TIM

This article claims that it does (airfoil shape). But who knows, as we still argue about "what causes lift".

umm..I say again, airfoil shape has it has little to do with it on CONVENTIONAL aircraft which normally takeoffand land WITH flap. On WIG aircraft that CRUISE in ground effect WITHOUT flap, airfoils are offcourse of importance!Do we have an "what causes lift" argument? Guess I missed that part... :( M

Told ya Larry....

Just because I like the sound of my own vioce I'll repeat: "This isn't meant to be an X-Plane/FSX slagging match."

True, but as usual, an "XPer" was the first to cast a stone saying MSFS cannot simulate this stuff...*sigh*FS9 vs XFSX vx XPCoke vs PepsiATI vs nvidiaThe list goes on... till the end of time!

True, but as usual, an "XPer" was the first to cast a stone saying MSFS cannot simulate this stuff...*sigh*FS9 vs XFSX vx XPCoke vs PepsiATI vs nvidiaThe list goes on... till the end of time!

Perpetuating it and stoking the fire doesn't really exclude you from the argument.How many FSXers have cast the first stone and said FSX is better than X Plane in X Plane forums around the virtual aviation world?Jim Skorna (FS.com mod and Activesky support person) even felt the need to post how inferior X Plane is in the FS.com forums. One of his observations? X Plane has only 1 default aircraft. Shows how well informed some people are. At last count, it was 52.

Told ya Larry....

Not quite yet....I want to know why the default X-Plane RV's pitch up like a Cessna, when flaps are deployed. Is it because the author just assumed that all planes pitch up, and it's a setting within the program..............or did "plane maker" fail? As to "lift", it's been debated all of my life, without the perfect answer. That may never change. But I always do wonder where "space" and all of the billions of galaxies end though. L.Adamson

Not quite yet....I want to know why the default X-Plane RV's pitch up like a Cessna, when flaps are deployed. Is it because the author just assumed that all planes pitch up, and it's a setting within the program..............or did "plane maker" fail? L.Adamson

Planemaker is a generic program. It makes sense that it is because Austin cannot write different programs for different planes. So there are settings in the control geometry section that you can adjust. All these settings are set at default values and calculate a certain value based on user input for the wings and certain airfoil types. THIS is why most add ons come out wrong. Developers assume planemaker knows what they want and they don't bother testing. The Duchess I made had this problem. When I tested it, I adjusted 1 setting and all was fixed. BTW, Morten told me about that setting. It now pitches down with flaps deployment just like the real aircraft.You mentioned the majority of add ons fly incorrectly because of Planemaker. This is incorrect. The majority of add ons fly incorrectly because developers don't know how to use planemaker. Planemaker is extremely versatile and accurate. But it's only as accurate as the developer using it. Just like FSX's SDK...only more accurate. ;)Hence Mortens Piper Archer. My Duchess. Tested by 2 Duchess pilots and they couldn't fault it. Tom's MU2. Nils' BK 117...probably 2 of the best payware adds on for x plane. How is it we all could make accurate flight models in Planemaker where others fail using the same program?

Austin doesn't have to write different programs for different planes, what he needs to do is enter existing data on standardized airfoils. The kind you would find in a duchess. So i'm not surprised it's amazingly accurate. But don't expect it to work on a 787 wing, not that the tool was designed for that purpose. At the end of the day they both spit out tables, just the ones from Planemaker are generally more accurate since it always convergent. FSX flight models are "copy paste" type deals You basically inputing numbers in a table that don't actually exist in the real world because real aircraft are designed for 17 different flight profiles, so again use your imagination here....