Game 'physics' realism VS 'aircraft systems' realism

[WestAir 2,524]

4 minutes ago, Bobsk8 said:

And pilots and their passengers die doing just that. 

Dozens a year! I edited my comment to remove that part because I wanted to stick to feasibility, but since you caught me before the edit, I want to link another video:

There is no way any of us would see the below landing done in MSFS and think for a second it was realistic. Turns out...

 

Edited May 11, 2022 by WestAir

[lwt1971 7,441]

I think in terms of systems simulation in MSFS it all comes down to the individual aircraft developers and how deeply or not they want to simulate stuff.

In terms of aerodynamics/physics I really don't think anything particular in the core sim stands in the way of aircraft developers being able to simulate most kinds of aircraft (I guess delta-wing birds are not facilitated well yet). Given the core physics/aerodynamics as outlined in https://docs.flightsimulator.com/html/Samples_And_Tutorials/Primers/Flight_Model_Physics.htm, and new innovations like soft-body physics, CFD via Navier-Stokes equations solving (definitely worth reading MS/Asobo's dev docs on this: https://devsupport.flightsimulator.com/storage/attachments/2425-debug-aircraft-cfd.pdf), etc I'm confident that the core aerodynamics/physics is quite sound... and it'll only keep getting better in future updates.

Given what various major aircraft developers have said (PMDG's RSR, iniBuilds, FBW, etc) about the core flight-model/aerodynamics in MSFS being on par with other sims and at times even better ... and similarly what various IRL pilots have said (whose opinions I value a lot), I think MSFS is in a pretty good place here. Flying the likes of the default Cessna 172 after SU9 with CFD enhancements, the Milviz C310, PMDG 737, etc I personally find the physics/aerodynamics to be pretty dang good, and definitely equal and actually better in some areas compared to my times with X-Plane 11 or P3D.  Also looking forward to further advancements coming due to helicopter and glider support in MSFS.

I always hark back to my times with Flight Unlimited as my best ever flying/aerodynamics experience from the past, and currently MSFS with the latest aircraft is the only sim that gets me back to that experience! But once again I'm no real-life pilot so I also pay attention to the praise coming from various IRL airliner and GA pilots out there along with what the prominent aircraft devs are actually saying about MSFS.

Edited May 11, 2022 by lwt1971

[jcomm 5,961]

9 minutes ago, lwt1971 said:

I always hark back to my times with Flight Unlimited as my best ever flying/aerodynamics experience from the past, 

👍That makes 2 of us 🙂

[ShawnG 1,823]

Skiathos is only about 300-400 feet longer than EGLC and they operate 757’s out of there that have similar takeoff specs.  Like the OP, I am not a real pilot, but I’m thinking the published specs for aircraft aren’t necessarily the bleeding edge performance data, but more likely with safety margins added.  EGLC, given that it is surrounded by London makes this more important.

[sd_flyer 6,072]

We have to open rubric "stuff you don't do in real life because it's unrealistic except you still do on occasion " LOL

 

https://www.youtube.com/watch?v=gXL1qQMky2w

 

 

[Bad_T 581]

oh wow thank you very much for all the inputs guys 🍻, interesting to read. Was really curious about what more experienced people than me would think about this and cool if that's quite realistic and possible even if no one would obviously test that in real life to make sure it is 🙈.

I thought that those parameters would be completely off limits for a safe takeoff but that's probably because I watched too many 'Mayday' episodes 😁🤣 that are made for the general public (like me) and a bit too simplistic (like they crashed because they forgot the flaps or were a bit overweight) So, in my example, by exceeding all limits by a very large margin (MTOW over 50 tons i think, can't remember exactly so i might say something stupid here) and breaking all possible rules at the same time i thought it would just be way too much for an aircraft to handle. But yeah, there's probably a large safety margin between what is not allowed and what is really catastrophic and rightfully so 😱.

yeah @omarsmak30 i know, the 737 is not the only 'study level aircraft' was just an example because it's the 'hot plane of the week' 👍 and in general there are lot less discussions commenting the 'flight dynamics' compared to 'systems accuracy'. For now i only have the 737 and maddog that i think are considered as 'study level' (i also have bought the crj but that one is probably a bit less aimed at being high level) but I will probably sooner or later fall for the 146 (then maybe even the c310, c414, and certainly the a320 when it's out... oh well just too many good stuff released lately and so little time, for sure a very good time for flightsim lovers).

Sometimes, for me in the sim, everything seems a bit too linear and quite easy a bit like 'on rails' while when i'm on real plane all seems quite a bit more lively (especially when they are small). Also when looking at real landing videos the pilot seem to be very active while in the sim very minimal inputs are usually good enough. So i was really interested in reading in what other people thought about it and it's nice if most real life pilot think it's quite realistic after all.

Thanks again, learning a bit every day is the way to go 🍺

Edited May 11, 2022 by Bad_T

[sd_flyer 6,072]

4 minutes ago, Bad_T said:

 

Sometimes, for me in the sim, everything seems a bit too linear and quite easy a bit like 'on rails' while when i'm on real plane all seems quite a bit more lively (especially when they are small). Also when looking at real landing videos the pilot seem to be very active while in the sim very minimal inputs are usually good enough. So i was really interested in reading in what other people thought about it and it's nice if most real life pilot think it's quite realistic after all.

Thanks again, learning a bit every day is the way to go 🍺

I have been flying in real life for 20 years. All airplanes I fly in real life are flown by me like their on rails (in smooth air) . So when my students make plane more "lively" we quickly fall back on fundamentals pitch attitude, power settings, trim. I always tell them good student should make their instructor to fall a sleep!

So please don't confuse perception on how airplane should fly  with how airplane actually fly. There are joes and there pros in aviation! LOL

[Bad_T 581]

yeah and perception of people not flying regularly is also probably a bit biased by the fact that you are really there and not just sat down on a chair. But yeah it's cool to know that everything we have in the sim is quite realistic 👍

Edited May 11, 2022 by Bad_T

[Fiorentoni 4,290]

You have to keep in mind that the "physics" is still code, that is not even close to the complexity of real life physics. While the 737 e.g. may be spot on for normal operations (which pilots apparently confirmed), it does not mean that the same code is able to also realistically determine the outcome of stuff that no one in real life would ever do. I do however assume that a 737 above MTOW with flaps 0 should not be able to easily takeoff from EGLC. Else one could easily let go with take off performance calculation because it will take off even in the worst of all cases. Not quite what I except from a study level aircraft.
Has anyone repeated that test?

[WestAir 2,524]

A lot (all?) of those accident where airplanes ride ground effect to the scene of the crash are airplanes using derated thrust and rotating well below what would be Vr at flaps 0. They're also (all?) flying low bypass turbofans, instead of the big and powerful engines of today. A better test would be to try your same scenario using the LSH Maddog since it uses JT8D's, set a derated thrust, and take off with flaps 0 at Vr speed for flaps 15. I'd bet good money that you'll drag the tail all the way into the water.

I don't think there's much difference in the available data between the 737-700 and the MD-83, so from a simulations standpoint, as long as PMDG and LSH both used all the published data, the accuracy of the edge of the envelope flying should be fairly consistent here.

 

 

[jcomm 5,961]

12 minutes ago, Fiorentoni said:

You have to keep in mind that the "physics" is still code, that is not even close to the complexity of real life physics. While the 737 e.g. may be spot on for normal operations (which pilots apparently confirmed), it does not mean that the same code is able to also realistically determine the outcome of stuff that no one in real life would ever do. I do however assume that a 737 above MTOW with flaps 0 should not be able to easily takeoff from EGLC. Else one could easily let go with take off performance calculation because it will take off even in the worst of all cases. Not quite what I except from a study level aircraft.
Has anyone repeated that test?

That's a very good point @Fiorentini. Actually flight simulators not meant for aerobatics or sport flying should be oriented towards accuracy "within the normal flight envelope and operations" and mostly procedurely. 

In times of FSX and P3D there were some good examples. MFS adds some bells & whistles, not only graphically but even in the way it models the amtmosphere and it's interaction with the aircraft.

I did not but the 737 because I am actually waiting for the FBW A380 which I believe will be payware, but I am sure PMDG programmers have done their best to make it perform close to the numbers...

Edited May 11, 2022 by jcomm

[robert young 2,897]

6 hours ago, Bad_T said:

So I was just wondering if this is just normal and everyone gets on with it just fine (although some people do complain for other small stuff that seem irrelevant to me like, you know, a screw texture not being 100% realistic or a circuit breaker not modelled 😁). Maybe we can get a very high degree of 'systems simulation' but are still very limited with the 'physics' part of the sim ? Or maybe it's just 'if you do a stupid test you can expect stupid results' 😱🙃😁

Thank you 🍻

 

When judging physics one has to discuss which part of the flight behaviour is in question. When developers say "tested by real pilots" this could mean many things. It could mean that climb performance at various altitudes, pressures, temperatures etc and broadly stall speeds at given AoAs, etc etc seem ok. But that leaves out several other vital things mainly connected with handling. Does the aircraft roll, yaw, pitch in authentic ways? To me those three elements are extremely important, because they are intimately connected to handling. You could have a sim aircraft that reaches the book ceiling in the correct time given its fuel and passenger load and power settings, but it could still handle like a pig.

How does the aircraft flare, or rotate? Or handle on the ground with nosewheel steering and rudder? At what speed does rudder authority become effective? Can it side slip in a believable way (GA aircraft). Does it drop a wing on stalling. Does it weather vane convincingly or drift in yaw believably. These are all factors that are not connected with what is generally accepted as "performance" yet they are pertinent to overall physics.

A given sim aircraft might fly beautifully in manual mode but is flawed under autopilot.  Or the reverse. There are so many facets of flight modelling that it is often very difficult to judge. Moreover, if a sim aircraft is "tested" by experienced pilots on type but who are not at all experienced running a given sim, they might lack the knowledge to set up their hardware and sim options to properly judge a given aircraft.

In my experience the best testers are those who are experienced on type in the real flying world AND in a given sim. Many real world pilots can be quite forgiving of handling deficiencies because they might assume a sim is incapable of reacting in the proper way to inputs and are eager to allow leeway. That was certainly the case when some of the first few "real pilots" published their initial reviews of MSFS. Many of them ignored the grossly exaggerated response to pitch input of some default aircraft. 

It's a very complex subject and one to be taken with a pinch of salt unless you are absolutely sure the tester concerned understands with great detail how a given aircraft should respond. I have known many pilots who are thoroughly attuned to how aircraft should behave and most of them are gifted aerobatic pilots flying smaller aircraft whose capabilities they are pushing to limits constantly. The more "procedural" large passenger aircraft become, the more scope there is to pass a sim aircraft as authentic because it seems to perform "by the book" within quite limited parameters.

The larger the aircraft, the easier it is to miss some handling flaws because it is assumed almost all flying is within the quite limited scope of take off, climb to cruise, gentle descent and Lnav and Vnav response. In other words the testing is often biased (quite understandably) towards autopilot capabilities. As to being surprised that a 737 can take off heavily loaded on a relatively short runway without flaps and so on, it must be remembered that most passenger aircraft are routinely flown within extremely strict limits. To watch what they are really capable of, one might look back to airshows like Farnborough or equivalents when huge new aircraft whose manufacturers were eager to impress potential buyers would climb at extraordinary rates, roll, pitch, take off and land in breathtakingly impressive ways (and of course they were typically almost empty of fuel and passengers).

 

 

 

[Bad_T 581]

interesting read @robert young, yeah for sure my original test example is ultra simplistic and borderline 'stupid' and doesn't even make much sense because you wouldn't judge a sim just based on that example. The process of creating these simulators in a realistic way is certainly a huge task but it looks like most people think it's a decent representation of the what's going on in the real world which is more than cool enough for me as a pure amateur.

🍻

Edited May 11, 2022 by Bad_T

[RaptyrOne 1,447]

Multi engine aircraft will always perform better than published data might imply as published performance data must consider losing a critical engine past V1. That means the aircraft must continue to fly on one engine under those temp, altitude and weight conditions. Having that 2nd engine will always make it seem like you are well above the limits and you are, until that engine pops on rotation.

[flying_carpet 657]

1 hour ago, robert young said:

When judging physics one has to discuss which part of the flight behaviour is in question. When developers say "tested by real pilots" this could mean many things. It could mean that climb performance at various altitudes, pressures, temperatures etc and broadly stall speeds at given AoAs, etc etc seem ok. But that leaves out several other vital things mainly connected with handling. Does the aircraft roll, yaw, pitch in authentic ways? To me those three elements are extremely important, because they are intimately connected to handling. You could have a sim aircraft that reaches the book ceiling in the correct time given its fuel and passenger load and power settings, but it could still handle like a pig.

How does the aircraft flare, or rotate? Or handle on the ground with nosewheel steering and rudder? At what speed does rudder authority become effective? Can it side slip in a believable way (GA aircraft). Does it drop a wing on stalling. Does it weather vane convincingly or drift in yaw believably. These are all factors that are not connected with what is generally accepted as "performance" yet they are pertinent to overall physics.

A given sim aircraft might fly beautifully in manual mode but is flawed under autopilot.  Or the reverse. There are so many facets of flight modelling that it is often very difficult to judge. Moreover, if a sim aircraft is "tested" by experienced pilots on type but who are not at all experienced running a given sim, they might lack the knowledge to set up their hardware and sim options to properly judge a given aircraft.

In my experience the best testers are those who are experienced on type in the real flying world AND in a given sim. Many real world pilots can be quite forgiving of handling deficiencies because they might assume a sim is incapable of reacting in the proper way to inputs and are eager to allow leeway. That was certainly the case when some of the first few "real pilots" published their initial reviews of MSFS. Many of them ignored the grossly exaggerated response to pitch input of some default aircraft. 

It's a very complex subject and one to be taken with a pinch of salt unless you are absolutely sure the tester concerned understands with great detail how a given aircraft should respond. I have known many pilots who are thoroughly attuned to how aircraft should behave and most of them are gifted aerobatic pilots flying smaller aircraft whose capabilities they are pushing to limits constantly. The more "procedural" large passenger aircraft become, the more scope there is to pass a sim aircraft as authentic because it seems to perform "by the book" within quite limited parameters.

The larger the aircraft, the easier it is to miss some handling flaws because it is assumed almost all flying is within the quite limited scope of take off, climb to cruise, gentle descent and Lnav and Vnav response. In other words the testing is often biased (quite understandably) towards autopilot capabilities. As to being surprised that a 737 can take off heavily loaded on a relatively short runway without flaps and so on, it must be remembered that most passenger aircraft are routinely flown within extremely strict limits. To watch what they are really capable of, one might look back to airshows like Farnborough or equivalents when huge new aircraft whose manufacturers were eager to impress potential buyers would climb at extraordinary rates, roll, pitch, take off and land in breathtakingly impressive ways (and of course they were typically almost empty of fuel and passengers).

One of the best articles I've ever read here. A bit longish 😉, but very accurate. In short, it describes the plane reviews we usually see at YT as, like it is for cars. A review there is how it looks, how it drives (in normal operation), how much it costs, etc.. But not doing a real test by pushing it to the limits and the values for the acceleartion values, brake distance, real mileage, interior noise level etc. measured by the car magazine.