Any updates on this issue?
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In the SDK description of the flight model, there is a listing of the aero parameters from the flight_model.cfg file. There is a color coding (not described) for each of the parameters. The type font color is either red or black, with nearly all of them being black. I believe that the red ones are the only ones used in the modern flight model, while the black ones are legacy parameters.
lift_coef_ground_effect_mach_table is in black, meaning (I think) that is it not used in the modern flight model. I just did some testing using values 0.0001:10.0, 1.0:10.0 and 0.0001:0.0, 1.0:0.0 and did not discern a difference. (If this table is consistent with their other mach tables, the first number is Mach and the second is the scalar applied to lift for ground effect.)
So, it looks to me like ground effect is hard-coded in and is probably based on parameters like wing span, wing area, wing location (high or low), and, of course, airspeed.
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This is a major issue with many aircraft, even the one that should be about as correct as possible, the 172.
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Brief description of the issue:
When landing airliners (B748, B787, but haven’t really flown anything else to check if it is present on other aircraft) at Vref speed as indicated on the FMC, after cutting power at ~30ft and beginning to flare up, the aircraft starts climbing initially and then floats about 10ft above the runway.
Provide Screenshot(s)/video(s) of the issue encountered:
Video can be found here;
Details;
A landing at KSLC (Salt Lake City) in the clear conditions preset showing off the ground effects which I think are way too exaggerated. I had to reapply power after the aircraft started climbing and then floating down the runway, and ended up getting a touchdown speed of -72FPM according to Gees landing analysis.
Aircraft had a Vref speed of 146kts at 30deg flaps (which was set) indicated on the FMC.
Aircraft had a payload of 116,540lbs (shown as 25.80% on the weights screen) and fuel load of 49,154lbs (shown as 12.00%). It was well within CG limits.
Sim version is 1.12.13.0. (Sim update 2).
Detail steps to reproduce the issue encountered:
Land an airliner at an airport.
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Same again, but in the 787-10 at maximum landing weight.
"A landing at KSLC (Salt Lake City) in the clear conditions preset showing off the ground effects which I think are way too exaggerated.
Aircraft had 30 degree flaps set, however I don’t know what the Vref speed was as since the 1.12.13.0. (Sim update 2) patch this sometimes doesn’t appear on the PFD on my system. I used a speed very close to other landings that I have done with similar landing weight where the Vref speed did show.
Touchdown of -382FPM according to Gees landing analysis.
Aircraft had a payload of 123,340lbs (shown as 52.30% on the weights screen) and fuel load of 22,367lbs (shown as 10.00%). It was well within CG limits.
Sim version is 1.12.13.0. (Sim update 2)."
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Glad we got a thread started on this.
yesterday I did a test comparing the legacy vs. modern flight model, and as bizarre as it is for me, the legacy flight model seems to behave much more realistically on landing.
realize that in the modern model the plane tends to go up again even with raised spoilers and autobrakes. and speed below the minimum lift speed …
I realized that from 80knos if you pull the stick, the a320 raises its nose in a frightening facility as if it has no inherence.
my conclusion is that i find the MSFS flight model much more dynamic than the other sims when the aircraft are in the air. however, landing is one of the worst physics, not to mention the fact that the control surfaces of this simulator are so sensitive (probably due to this problem of inertia).
OK so I wasn’t going insane after all.
After about a month away from MSFS (1 week of P3D4 and 2 weeks on a business trip flying an actual airplane) I fired up MSFS only to notice that I had to effectively pitch DOWN to force the airplane onto the ground - this applies to everything from the Mooney to the 747, but the more pronounced the larger the plane. And yes, I’m flying these aircraft at the appropriate speeds for their weight/altitude combinations, so it’s not an issue of the plane simply coming in too fast on approach and ballooning like you see in so many student pilots IRL.
It feels like as you approach the surface of the runway, a giant invisible magnet is repelling the aircraft until it suddenly gives way when the aircraft is moments away from stalling.
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For props. indeed the propeller drag seems to be completely missing, I’m also not sure if the propeller spoils the air behind it over the wings MSFS…
As for swept wings, the CL / a curve is much more flat when compared to a straight wing and ground effect should therefore have a smaller effect. Additionally there might also be a drag issue here.
But on airliners the center of lift is acting in front of the center of gravity, the stabilator forces are reversed, in short the complete force balance is wrong so what do you expect 
…
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I’m sorry, did you mistake us for a bunch of aeronautical engineers up in here?
Seriously, this is interesting. Are you saying that in general, small GA planes are designed so the CL is behind the CG, whereas on airliners it’s reversed – the CL is in front of the CG? That would mean the tail in small planes would have to exert a relatively constant downforce to stay balanced, while an airliner’s tail would have to exert an upwards force, right?
Why the difference? Is one more efficient than the other? Or is it a function of the higher speed? Airfoil shape? Curious minds want to know!!
B
It is the case in MSFS somehow. In real life the center of gravity is located in front of the center of pressure, at least in the normal flight envelope creating a nose down moment which is compensated for by downforce on the horizontal stabilizer. This is no different than a small GA aircraft. In MSFS this is completely reversed as can be seen in the dev mode.
It would be more efficient to have the CP located in front of the CG with an up force on the horizontal stabilizer, unfortunately it doesn’t work like that as this would cause longitudinal static instability.
I read this, but my mind only registered, “Something…, something…, Airbus…, Boeing…, Developer mode.” I need to eat some dinner and get some rest, and then I promise I will wade through the linked thread and even upvote it because I know you know what you’re talking about. I will, however, also do some research on my own to increase my own knowledge of the subject.
I’ll probably take a couple of Advil to ward off the headache that’s sure to follow! 
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It is a difficult subject, maybe one of the most difficult ones aerodynamics wise. But I’m sure it has something to do with a lot of faulty flight dynamics including the endless floating over the runway.
For example, normally in ground effect the angle of attack on the stabilizer reduces due to the wing downwash reducing (basically the ground is in the way) normally the stabilizer is keeping the nose up, if the stabilizer downforce reduces the nose will drop. Since in MSFS this is working in reverse and the stabilizer is keeping the nose down, the nose will pitch up in ground effect.
This might explain part of the endless floating and people needing to force the aircraft onto the runway by pushing the nose down. In real life you always need to apply backpressure in ground effect to prevent the nose from dropping. As speed reduces it requires more and more stick force to keep the aircraft off the runway.
Edit: found this on Google, a simple illustration of the reduced downwash angle from the wing onto the tail. It will probably be less profound on a jet but the effect is still there.
As a pilot, this I understand and agree with. In the small planes I flew, you learned to do full stall landings, but eventually you usually did close-to-stall landings unless you were landing on a short runway. And you usually touched down on the mains, and kept the nose wheel off pretty much as long as you could. That meant pulling the yoke further, and further, and further back as the elevator lost control authority due to lack of speed. The yoke ended up in your lap on good landings.
The sim does not feel right in that regard. You don’t have to pull the yoke back because the nose wheel hangs in the air even at very low speeds. That’s another way of saying what you said – endless floating and the need to manually push the nose down.
Agreed: Either it’s not modelled correctly, or it is, and the flight model config file parameters are not set or used properly.
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Something…, something…, that’s one of the reasons they invented the T-tail?
A T-tail is more efficient as it is above most of the wing downwash and disturbances. Its more effective down to a lower speed as it is mostly in undisturbed airflow the CG range is often larger with a T-tail also. Drawback is that a T-tail keeps “flying” and therefore keeps the nose up during a stall where a conventional tail will be in the wings disturbed downwash and automatically lowers the nose (self-recovery). With a T-tail you normally need a stick-pusher to accomplish the same, with manual flight controls you also miss the tactile clues of a stall with a T-tail therefore you often have a stick shaker to artificially create those. It is also heavier contruction wise.
I did notice indeed that the nosewheel stays in the air for a long long time on the TBM and you need to push the nose down in order to get it on the ground . There definitely is something wrong there, maybe lack of downwash modelling, maybe something else… Maybe the dev mode can give some answers. I hope they have some good news for us in the next feature discovery series about aerodynamics…
Flying the TBM930 with the TBM improvement mod I have no issues landing by the book.
Approach speed 85 KTS and gradually reducing to flight idle once over the runway threshold, start the flare to touchdown on the main gear and she greases it at 70KTS on the touch down zone.
Weight usually about 6500lbs.
I’m not saying there isn’t an issue with flight model but for me the TBM930 flys according to the POH on landing anyway…
If that’s the mod I think you’re referring to, the original author was a real TBM pilot and knew how it should behave. The mod tweaks the flight model and engine config files to be more realistic.
These threads are supposed to be discussing the default aircraft behavior, not with mods. As the topic title says, the landing physics of all default aircraft – no mods – are not realistic, and one specific problem is the way the aircraft float in ground effect. If you agree that the unmodded TBM does have this ground effect problem, please give us your vote.
Ok wilco, I’ll remove the mod and get back to you.
Thanks
Ok so I did a couple of quick tests by flying six touch and go’s at two different airports (three at each)with the mod first to get a control as that’s what I’m used to. I’m new here and have only really flown with the mod.
Then I removed it and did the same landings. The thing that struck me was the lack of drag from the landing gear (presumably). On average I floated further down the runway by a second or two.
When I deliberately slowed to 80KIAS or just under I touched down at the same spot but minus 5kIAS on average (from about 68-70 down to 63-65).
After the two tests I reinstalled the mod and repeated the test. More drag and less end float therefore more power on approach and a quicker settle when power off at the threshold.
So yeah, I’ll vote this one.
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