I appreciate you taking the time to reply and be informative and non-confrontational.
Well I enjoy understanding physics by playing with it, is that called applied physics? not Theoretical physics? Well, Why does the 787 in FS2020 stall at 120 knots while having max weight. While in X-Plane 11.52, I seem to bring the aircraft to the ground with gusting winds and I don’t seem to have those intense feelings of holding onto the stick in FS2020? What needs to change in my Joystick settings maybe or in the CFD file? or invest another 150 USD for an addon in another 2 years? or may be 5 years?
Please help, I love the graphics of FS2020… Please.
Perhaps what they’re saying, based on your statement that they model propwash, it sounds like Microsoft calculates the flow over the surfaces and iterates that like a non-linear structural analysis would, to figure out which surfaces might be blocking others, and therefore are able to come up with an accurate picture of occlusion and flow change from one surface to the next.
Perhaps what X-Plane is doing, based on what was said above, “We know what the flow from the propeller is, now we’re going to explicitly add that flow to the the flow over the tail surfaces” So, sort of skipping the iterative flow calculation step.
In the end, it’s all just an engineering analysis to calculate a resultant number, or rather matrix, to describe the orientation and velocity of an aircraft at any given moment. To me, it sounds like we’re going from a 5 element beam element model of the bending of a pencil with FSX, to a several thousand element non-linear structural contact analysis with MSFS.
Does that mean, that soon we will have the real 787 on FS2020?
And I don’t need to buy PMDG? Thank you very much for your applied physics demonstrations of my understanding.
- Velocity Determination
This is done twice per cycle. The aircraft linear and angular velocities, along with the longitudinal, lateral, and vertical arms of each element are considered to find the velocity vector of each element. Downwash, propwash, and induced angle of attack from lift-augmentation devices are all considered when finding the velocity vector of each element.
Propwash is found by looking at the area of each propeller disk, and the thrust of each propeller. Using local air density, X-Plane determines the propwash required for momentum to be conserved.
Downwash is found by looking at the aspect ratio, taper ratio, and sweep of the wing, and the horizontal and vertical distance of the “washed surface” (normally the horizontal stabilizer) from the “washing surface” (normally the wing), and then going to an empirical look-up table to get the degrees of downwash generated per coefficient of lift.
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Well, I have a feeling you’re going to have to wait for a little while.
Currently, the wind modeling in MSFS is pretty borked at ground level, and I believe their modeling of the rudder surfaces also needs some work. Doing cross-wind landings in MSFS, there seems to me to be something wrong, I just can’t get it right.
They are doing some things in Sim Update 3 around wind modeling supposedly, although I don’t know if it goes to that level of detail.
You know, reading through all the bugs and wishes, I’m not seeing things that people who fly are asking for in flight model accuracy. Hopefully Asobo is listening though.
But, I’ve never flown a 787 in real life, not in the cockpit, and not even in a passenger seat. I imagine it has a flyby wire system, however though, no? I’m not sure how they model forces in the stick in the real plane if it is, if they even do. I do remember discussions about the first FBW system in the F-16, it was just a solid stick with no movement, and pilots hated it, so they add some flexibility to the mount. I don’t think it had any force feed back. IOW, probably get a motion chair, and maybe a stick that has a little more resitance to its movement, so you can’t over control the plane at any given moment. Not that it’s your fault, it’s just the nature of these controllers.
but going by the information from multiple sources the “legacy FM” is for FSX aircraft imported into MSFS, which if we take that as true, then that is the “bridge” between historical FSX methods and the new methods as a hybrid FM, while “modern” is a stand-alone stripped of the “bridge” so to speak.
What does this mean? I don’t understand, Do we have real physics on FS2020 with real corrections to the strong gusting winds? But then how did the Aircraft fly with no wind in the First BUG of FS2020, While all over the planet there was only one 223/5 wind present, How do strong gusting winds apply to the real physics of FS2020, I want to fly today, with the sunshine and clouds that will make my aircraft feel like a bird strick and not like a stone falling from heaven of Marketing Skills.
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So, that sounds exactly the same as what MSFS is doing, with a whole lot less detail about what’s actually going on. Did you read through my posts in detail above? It is pretty interesting.
Basically what the SDK says, as I repeated, X-Plane is only looking at the wings and tail surfaces and propeller (which your article doesn’t even mention). Those are the parts they discretize and calculate on. Your article seems to support that as the only item they talk about discretizing is the wing.
The SDK goes into a bunch of detail about the iteration process they are using to calculate the forces on all the surfaces they use. The article you posted brushes on that subject and kind of mentions it.
I don’t see anywhere that X-Plane uses the visual model to calculate anything. I feel sad if they do, as I seriously doubt the accuracy of most models geometrically. Just like a finite element model, they are all reducing the plane to a smaller series of parts and then solving those parts individually based on the forces acting on them, and then solving all those equations simultaneously until the system balances and forces equal to zero.
From the article you posted, X-plane splits the wing up into 10 pieces, MSFS into 400 pieces for each wing.
So fuel consumption on a swept wing does not change the center if gravity if I understand this correctly? The fuel tank is just a box…
What I posted is they discuss how they calculate the aerodynamic forces on the various parts of the plane. In the case you are asking about, that would be external fuel tanks and the aerodynamic forces.
The point being, MSFS takes the landing gear and external fuel tanks into account, while X-Plane does not. INTERESTINGLY, MSFS does not take the propeller into account!!! Not in this discussion anyway. I dunno who made that decision.
Earlier in the flight model they do discuss the values used to allow the user to adjust the CG based on the load, but they don’t talk about whether they recalculate that load over time as fuel is burned.
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Can you please explain, if there is such a big difference between the number of points of measurement on the wings and around the aircraft, why does the 787 Stall at 120 knots with max weight? and Takeoff with small fields even at 110 knots? do we need more points of calculations to improve on the stall speed? Please explain to me where do I change the stall speed? So I can really feel the 787 come close to the ground in the gusting wind and really stall with the right angle.
Oh, but it specifically mentions the propeller and effects related to it?
I skimmed your articles, but it’s 5 am here for me, so a detailed read will have to wait.
Anyway, the main difference is that FS uses precompiled values from tables, which XP supposedly does not do and instead calculates the fluid dynamics in real time.
It’s very well possible that FS model can be more detailed and granular in some aspects, but right now it makes many concessions to please casual flyers with missing or “tuned down” physics.
Which means that if I fly with full load on the 787, I will fly at the same speed with the same power?
Is that real physics? or do I need to study physics from Microsoft Marketing skills…
I have a feeling, in the end, X-plane does the same thing. But I’d have to research that. The article you posted supports my feeling, but doesn’t substantiate it.
No, they do take the total weight into account. I did not see any discussion that they reduce that weight over the period of flight and take that into account.
That doesn’t mean they don’t, it only means I didn’t see it discussed. They clearly know it’s been burned, so, my bet is they do. I just didn’t see it discussed. It’s possible I missed it, too. I’ll check now…
Ah sorry, I missed “external” fuel tanks, makes sense…
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I love FS2020 as much as the physics of X-Plane… Can you please tell me how do I turn on the physics, so I will have Temp. influencing MACH speed? or stall speed decreasing at ground effect? I would love to see the effects with real demo examples of your flying in the video, I am sure I would learn a lot from you. Thank you so much for your contribution… Love to fly FS2020 Physics.
I do think it’s kind of funny that they go through all these aerodynamic equations and body rotation and translation due to forces, and then come up and say, “Yeah, but we don’t do that” haha
As an engineer and analyst, I get why they are doing what they are doing, it just struck me funny.
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To be fair, that write up I posted is not as comprehensive as the SDK documentation. I am sure there is a more in-depth description available for XP as well in their SDK.