The Physics Model

[Chock 17,769]

10 minutes ago, BiologicalNanobot said:

That's... oddly specific 🤔

Maybe so, but frankly when people come out with that cobblers about Blade Element Theory being some magic bullet for flight sims, it's tedious. If that was really true, companies such as PMDG etc would have ditched MS Flight simulator back when FS95 was out, because XPlane was around then. I know, I've had every version of it ever and always buy it to support flight sims, but the idea that it's vastly superior to other PC sims is utter nonsense.

Edited March 28, 2021 by Chock

[Cai Zicheng 171]

49 minutes ago, Chock said:

'This research tool has been used to visualize flight paths, test control algorithms, simulate an active airspace, or generate out-the-window visuals for in-house flight simulation software'

So, not for actual flight modeling then; which is what we're on about here.

Seriously, you need to be aware that when Laminar bang on about this aspect of XPlane and Blade Element Theory etc, it's PR, it's the same as when PMDG go on about that 'within five percent' stuff and everyone just swallows it all up without looking into it in detail. Blade Element Theory was developed for testing underwater drive screws (propellers) on ships back when paddle steamers were still common; it's not some new magic flight modeling system.

Controls engineer here. The first requirement of a control algorithm test bed is that you have accurate dynamics to tune and test it on. Otherwise the control algorithms you built will be VERY off when deployed on real vehicles.

So if NASA says they are using X-Plane as control algo test bed, then it's a huge stamp of approval for X-Plane flight dynamics then anything else.

[Scottoest 1,561]

6 minutes ago, mtaxp said:

I will not talk more about x-plane since people are a bit sensetive here. But yes, aerodynamics are a part of it and there are specifc powerful tools that come even with the home version of x-plane, but also, getting a flight simulator flexibile and open enough to support this kind of developement is something really to no underwhelm, whenever I see MSFS (including their marketing team that claims it is superior) it kinda cringes me due to reality literally proves them wrong.

All I did is support my claims compared to a quote that vaguly quoted another, there is no reason to get mad (no directly to you).

Now i'll go..:-)

I'm pretty sure MSFS's "marketing team" have literally never said a word about X-Plane in this manner, if they've even mentioned XP at all.

[ComSimPilot 623]

I guess the only way to have a good answer to this would be from people who can fly the same plane in P3D, MSFS and in real life. 

[Biology 1,347]

28 minutes ago, abrams_tank said:

LOL, I don't think NASA is using XPlane for aerodynamics research. I trust that person's opinion, who at least did the math, over yours.

To be fair, X-Plane is more suitable for designing aircraft due to the way its flight dynamics engine works. X-Plane derives global coefficients from local coefficients and aircraft geometry, while MSFS derives local coefficients from global coefficients and aircraft geometry. This means X-Plane can be used to have a reasonably accurate estimate of aircraft behavior without building the aircraft and putting it in a wind tunnel, as it doesn't depend on global coefficients, which are only available after an aircraft is built and tested in a wind tunnel. MSFS on the other hand, relies on global coefficients, which is again not available until an aircraft is built and tested in a wind tunnel.

However, this thread is about accuracy of MSFS' flight dynamics engine, not about if it is suitable for designing aircraft or not. These are two different questions - a flight dynamics engine can be perfectly realistic even if it is not suitable for designing aircraft. For training purposes, only thing that matters is accuracy of the aircraft behavior, not where the performance data comes from. As I have demonstrated in one of my previous posts, MSFS' flight dynamics engine is already quite accurate unlike what some people claim, it just needs some improvements for Cm fit and compressible flow effects. X-Plane's flight dynamics engine is more accurate, but not by a huge margin.

Edited March 28, 2021 by BiologicalNanobot

[Scottoest 1,561]

2 minutes ago, BiologicalNanobot said:

To be fair, X-Plane is more suitable for designing aircraft due to the way its flight dynamics engine works. X-Plane derives global coefficients from local coefficients and aircraft geometry, while MSFS derives local coefficients from global coefficients and aircraft geometry. This means X-Plane can be used to have a reasonably accurate estimate of aircraft behavior without building the aircraft and putting it in a wind tunnel, as it doesn't depend on global coefficients, which are only available after an aircraft is built and tested in a wind tunnel. MSFS on the other hand, relies on global coefficients, which is again not available until an aircraft is built and tested in a wind tunnel.

However, this thread is about accuracy of MSFS' flight dynamics engine, not about if it is suitable for designing aircraft or not. For training purposes, only thing that matters is accuracy of the aircraft behavior, not where the performance data comes from. As I have demonstrated in one of my previous posts, MSFS' flight dynamics engine is already quite accurate, it just needs some improvements for Cm fit. X-Plane's flight dynamics engine is more accurate, but not by a huge margin.

You should really consider getting in touch with Asobo, because it seems like you'd have some valuable input as they tweak this stuff.

[Biology 1,347]

6 minutes ago, Scottoest said:

You should really consider getting in touch with Asobo, because it seems like you'd have some valuable input as they tweak this stuff.

I wish but I'm far from being qualified enough - I'm just taking an aerodynamics course and will start doing a double major on aerospace engineering.

Edited March 28, 2021 by BiologicalNanobot

[Chock 17,769]

20 minutes ago, Cai Zicheng said:

So if NASA says they are using X-Plane as control algo test bed, then it's a huge stamp of approval for X-Plane flight dynamics then anything else.

Where did NASA say this? Did you actually read that link?

[Glenn Fitzpatrick 3,798]

The issue with any flightsim is they are built by programmers not aeronautical engineers   😄

 

 

Here is Mike Patey on why he has spent over a year designing one wing for one aircraft, the server he uses for the analysis makes a 10900K 3090 rig look like a horse drawn cart:

 

 

 

[Gulfstream 416]

You can read all you want about the physics straight from Microsoft.

https://docs.flightsimulator.com/html/Additional_Information/Flight_Model_Physics.htm

It looks like the (I'm assuming) LaTeX markup isn't rendering correctly but the information is all there.

[Bob Scott 7,721]

I'm still waiting for an airplane in MSFS that actually demonstrates anything resembling the sort of superior flight model fidelity that is claimed.  To date, nothing comes anywhere close.  It's not an MSFS vs P3D thing, it's an MSFS vs their own advertising thing.  The proof of the pudding--actual performance in the sim--clearly justifies taking the claims made w/r/t the MSFS flight model with a healthy grain of salt...like the constant "turbulence" that keeps a light plane's nose hunting around in no-wind still-air conditions like a hound dog on a rabbit trail.

Plunking a bunch of theory from an aerodynamics textbook into your docs does not a working flight dynamics engine make.

 

[iCann 13]

When MS says it’s the same physics that is technically true, the real question is how and where that bit is implemented and at what priority,
previous iteration of P3D and MS FS up to 2020 flight physics were and still the core while everything else developed around that core,
In FS2020 it’s the other way around fight model physics were fitted into an existing complex world model with other physics priority, 
two separate elements that have different priorities and issues conforming with each other,

[Cai Zicheng 171]

2 hours ago, Chock said:

Where did NASA say this? Did you actually read that link?

Quoting yourself

'This research tool has been used to visualize flight paths, test control algorithms, simulate an active airspace, or generate out-the-window visuals for in-house flight simulation software'

[snglecoil 1,828]

My flight school has a Redbird TD2 which is an approved basic aviation training device. My students can log up to 10 hours of their instrument flight training on that device. I can log all of my instrument currency on the Redbird. It uses P3D as the underlying simulation software and high quality physical hardware controls. ....it handles so comically bad, I honestly am left shaking my head everytime I use it. BUT it is approved and does an excellent job as a procedural trainer which is the biggest advantage of a simulator. 

I'm all for P3D, X-Plane, MSFS, or whomever else continuing to increase the fidelity of their physics engine, but that is only part of a MUCH bigger whole. I think people put way too much weight on this topic especially when it comes to a home flight sim.

[SAS443 1,723]

21 minutes ago, snglecoil said:

...it handles so comically bad

ssssshhh. This is supposed to be a secret. The die-hard pixel pilots believes they are simulating near to life-like behavior with the professional training software that is P3D and MSFS is so unrealistic and arcade. Designed for gamers in mind, so "real" simmers should not bother.

You must not speak of this again.

Edited March 28, 2021 by SAS443