Game 'physics' realism VS 'aircraft systems' realism

[Bad_T 588]

ok hmm probably a very stupid thread, sorry in advance 🙈

now that we have 'study level' aircraft (which i really enjoy and find great so this thread is not a complaint at all, just an interrogation) i was wondering about some limitation in the 'game physics' or if it's just me making up things.

So last night i took my fresh new beloved pmdg 737 aircraft and did a somewhat stupid test :
- went to EGLC (small runway probably not certified for 737 i guess)
- put full pax / cargo
- put full fuel  (aircraft is now way above max take-off weight)
- set flaps to 0  (yeah crazy)
- put throttle to full without even using the toga switch
--> result no prob, it just took off fine (just needed a bit more trim and felt a bit heavy but other than that no prob)

Wouldn't that in real life be completely impossible and would lead to a catastrophic crash 99.9% of the time ? I'm not a real aviator, so i might be wrong. I didn't test the landings but probably an excess of weight on landing and no flaps would not cause much problems either.

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 🍻

 

[andreh 125]

Probably not impossible. It's just not allowed.

[qqwertz 812]

A RL B737 pilot would probably know those details, but if the engines have enough power (I believe they would), you could take off even if you are above MTOW. You would probably cause some damage to the engines, but that would not necessarily have immediate consequences. And you would violate a bunch of regulations. 

The physics in MSFS is actually very good by now. Not perfect, but my impression is that it even surpassed XP-11 at this point. You cannot take off with many smaller airplanes above MTOW, for instance. The air temperature and airport altitude matters. In the PMDG DC-6, temperature even has an impact on engine oil viscosity. Hence, my guess is that your test basically demonstrated that the 737 engines have a lot of power 🙂

 

[omarsmak30 4,069]

42 minutes ago, Bad_T said:

now that we have 'study level' aircraft

PMDG isn’t the only study aircraft for MSFS

[2reds2whites 827]

What weight does that actually take you up to?

In any case, it'd likely 'work' in real life just fine. You wouldn't meet regulatory performance requirements (balanced field, threshold +50ft, climb segments etc). And engineering would have a significant variety of checks to perform as you've over-stressed the airframe per its normal operating limits. In extremis your VLOF might be about the tire limit speed so you might have issues there. But inherently if there's enough air over the wings and it's not over-stressed to the point of destruction (which you wouldn't be) it'll physically fly.

Modern engines are so powerful. Remember that thrust requirements are such that you have enough thrust to go-around and climb with a total engine failure at decision altitude, at max landing weight, with full flap. Or to think another way, on a single engine failure on takeoff at Vr you have enough thrust to climb at max takeoff weight. 

Edited May 11, 2022 by 2reds2whites

[ha5mvo 262]

38 minutes ago, qqwertzde said:

The physics in MSFS is actually very good by now.

And how did you determine that?

The test done by the OP is actually a more reasonable method than a gut feeling or some general "it feels right" sensation.

That is not to say that what his attempt will be impossible IRL (while operating outside the safety envelope, of course). A comparison against some real world data could actually determine how good or bad MSFS physics actually is.

[abrams_tank 7,539]

24 minutes ago, ha5mvo said:

And how did you determine that?

The test done by the OP is actually a more reasonable method than a gut feeling or some general "it feels right" sensation.

That is not to say that what his attempt will be impossible IRL (while operating outside the safety envelope, of course). A comparison against some real world data could actually determine how good or bad MSFS physics actually is.

With respect to the PMDG 737 for MSFS, multiple real life 737 pilots have commented on it now: https://www.avsim.com/forums/topic/617802-collection-of-real-life-737-pilots-opinions-on-pmdg-737-here/

In fact, flightdeck2sim, another real life 737 pilot, said that the PMDG 737 for MSFS handles and performs better than the PMDG 737 for P3D on his Youtube live stream yesterday.

I would think real life 737 pilots know what they are talking about if they are commenting on the PMDG 737 in MSFS.

Edited May 11, 2022 by abrams_tank

[qqwertz 812]

33 minutes ago, ha5mvo said:

And how did you determine that?

..... A comparison against some real world data could actually determine how good or bad MSFS physics actually is.

I did exactly that, in two different ways. While beta testing the Milviz 310R, I had a lot of interaction with real life Cessna 310 pilots, who generally said that the model is very close to the real thing. Hence, if a developer is willing to adjust all parameters carefully, the MSFS physics model can produce very good results.

A second test I did was with another model that I am beta testing right now. I compared the performance at different power settings and altitudes to the POH of the real airplane, and found pretty good agreement (and that's still with a WIP model). I also compared the roll tendency with a (highly acclaimed) model of the same airplane in XP-11 and found that the MSFS WIP model performed better than the XP-11 model.

That's not to say the MSFS model is necessarily better than that of XP-11, it could also be that the third-party developer for MSFS puts more efforts into getting it right. However, MSFS is by now a pretty good flight simulator as far as the physics of flight is concerned.

[jcomm 6,068]

I have given up on questioning the physics in MFS... It's not up to the level of other flightsims I use / used, BUT !, for the kind of use I give MFS these days it serves it's purpose beautifully.

Scenery-wise it's 2nd to none, and while even a simple glider ( no fancy engine effects ) behaves unrealistically enough to have me shelved MFS long ago, truth is that instead I decided to use it "procedurely", benefitting from the really excellent graphics that can help me privewing my RL tasks and even the already available weather engine which, starting SU9, is really getting inetersting for soaring ! Also, this is good at least for as long as I wait for X-Plane 12 to get released and then decide if I can use only one of the two, or will be forced to use both...

In an airliner-type simulation I would again use MFS precedurely, forgetting about the limitations imposed by the flight dynamics - which is an ongoing task and ASOBO appears to continue to very actively develop.

And yes, I strongly belive a real 737 wouldn't be able to take off under such circumstances and from a 4948 feet rw...

Edited May 11, 2022 by jcomm

[sd_flyer 6,118]

2 hours ago, Bad_T said:

ok hmm probably a very stupid thread, sorry in advance 🙈

now that we have 'study level' aircraft (which i really enjoy and find great so this thread is not a complaint at all, just an interrogation) i was wondering about some limitation in the 'game physics' or if it's just me making up things.

So last night i took my fresh new beloved pmdg 737 aircraft and did a somewhat stupid test :
- went to EGLC (small runway probably not certified for 737 i guess)
- put full pax / cargo
- put full fuel  (aircraft is now way above max take-off weight)
- set flaps to 0  (yeah crazy)
- put throttle to full without even using the toga switch
--> result no prob, it just took off fine (just needed a bit more trim and felt a bit heavy but other than that no prob)

Wouldn't that in real life be completely impossible and would lead to a catastrophic crash 99.9% of the time ? I'm not a real aviator, so i might be wrong. I didn't test the landings but probably an excess of weight on landing and no flaps would not cause much problems either.

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 🍻

 

I'm pretty sure no real pilot tried this  to deliver you correct result, so nobody would know. However there is history of experimenting and putting things to the limit. For example

https://www.youtube.com/watch?v=uM5AI3YSV3M

[thepilot 602]

Look at the guy who stole the Q400 in Seattle some time ago. The maneuvers he did were most definitely way outside the flight envelope (barrel rolls and such), and yet the aircraft did not fall apart. In aviation, everything’s about contingency, and margins, in one way or another. You can probably take-off comfortably from an airport on two engines, but what if you lose one in the process? This where it could get delicate. 

[sd_flyer 6,118]

Here is another example. Ever heard about Bob Hoover? Yes it's impossible unless you of course Bob Hoover! LOL

 

[Bobsk8 12,952]

2 hours ago, qqwertzde said:

A RL B737 pilot would probably know those details, but if the engines have enough power (I believe they would), you could take off even if you are above MTOW. You would probably cause some damage to the engines, but that would not necessarily have immediate consequences. And you would violate a bunch of regulations. 

The physics in MSFS is actually very good by now. Not perfect, but my impression is that it even surpassed XP-11 at this point. You cannot take off with many smaller airplanes above MTOW, for instance. The air temperature and airport altitude matters. In the PMDG DC-6, temperature even has an impact on engine oil viscosity. Hence, my guess is that your test basically demonstrated that the 737 engines have a lot of power 🙂

 

I agree. I tried a takeoff at Aspen in the Cessna 310 R, density altitude was around 9800 feet, and it was a struggle to climb. Very realistic. 

[WestAir 2,530]

You're asking if a 737-700 can depart a 4,948 foot runway at MSL with standard pressure, full fuel, a lot of cargo and pax weight, and flaps 0.

There aren't any publications or tables to know the answer. You couldn't even try this in a Level D sim and expect a correct answer, because sims are built using observed data. Edge of the envelope flying, even using blade element theory and physics, will always be a thought experiment. To know if what you did is possible we'd have to get Boeing to try it and PMDG to simulate the new published data. Until that happens, every 737 sim is unrealistic, from ZIBO to PMDG to a Full Flight Sim. They're all guesses.

I imagine half of us would use the below video as evidence of an unrealistic simulation if it were a sim and not, in fact, real life:

Edited May 11, 2022 by WestAir

[Bobsk8 12,952]

12 minutes ago, WestAir said:

There are pilots who fly way out of CoG and MTOW in their Piper Seneca every single day. Right now someone is breaking more rules than you did and getting away with it just fine.

 

And pilots and their passengers die doing just that.