Please fix the Ground Physics (Friction, inertia etc...)

Bug Reporting Hub Resolved
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81

  1. I don’t mean moving laterally, if something is bobbing up and down they stay put.

  2. I can spawn a plane on the ship and it still kicks it off. Collision is fully supported by MSFS and i implement it on my models.

82

Yes, any changes to the flight_model.cfg file will take affect if you resync. It doesn’t matter whether or not you are creating a mod. Here’s one way to do it:

  1. Load the airplane for which you would like to look at the effects of some change in the flight_model.cfg file.
  2. In Dev mode, select “New Project” in the [DevMode} menu.
  3. Put in a project name (for example, “test”) and click on “Create new project.”
  4. In the Wizard selection box, click “cancel.”
  5. Under the DevMode “Tools” menu, select “Aircraft Editor.”
  6. In the Aircraft Editor window, you can now select “resync” under the “File” menu.

Resyncing will run the flight model optimization process, incorporating whatever changes you made to the cfg file..

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83

Great, thank you.

84

I just googled it, it is exactly 15 knots. I assume that’s for basic safety though, i.e. you can fly safely at 15, but beyond that you’re operating beyond the safety certifications in the POH. It doesn’t mean your plane would careen off the runway and you’d be unable to turn the plane to the right even with full yoke at 16 knots.

I’m glad Hobanagerik has looked into it. I’m a not an IRL pilot and no knowledge to articulate or understand exactly what’s wrong other than it’s behaving very weirdly. He’s been able to explain some of what is going on which is enlightening, and also encouraging that it will be corrected soon enough.

I’ve calmed down about it for now, and will just fly with the few clouds preset until it’s working or I learnt to fly something else.

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85

Feel free to try it again with both friction settings set to 10. It’s still challenging, but at least doable.

86

The max demonstrated crosswind is what an experienced pilot can safely operate the aircraft at. For an inexperienced pilot the safety margin would be lower. In the SIM the whole thing is exacerbated by the quality and tuning of the control peripherals. So should you careen off the runway at 16knots? Well, maybe! You can’t just put it all down to the SIM, although the friction and inertia physics clearly do need improvement.

For me it’s the landings that the limitations are most noticeable - inertia should do a better job of keeping you moving in a straight line just after touchdown, but instead the vaning immediately has full effect and off you go…

But even then it’s only relatively subtle tuning that’s probably needed - pilot skill still is probably a bigger factor: when I watch very experienced IRL pilots MSFS streams or vids they achieve consistently better landings and rollouts than I can ever manage in tricky wind conditions. And that’s down to the skill coming from thousands of hours of experience.

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87

Have somebody tested what those new lines do?

ground_crosswind_effect_max_speed = -1000 // feet per second, default is 80
ground_crosswind_effect_zero_speed = -1000 // feet per second, default is 5

88

Some interesting work reported above:

And this in a different thread:

Is there something going on with wind or runway friction? - #91 by Raynen

89

Thanks for the information :slight_smile:

but thats about the friction. The line i asked about is the thing about crosswind.

90

Same difference! The other two new parameters are to do with friction. The four are meant to be used in conjunction, not isolation I think. The base issue with ground physics is friction.

91

Look in the sdk documentation. There are good explanations to those variables there. They’re about cancelling out crosswind.

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92

One line states the minimum ground speed ar which crosswind will be felt. The other value is the speed that 100% of crosswind will be felt.

So you’ll experience no crosswind all all below the minimum, then it will gradually increase to 100% at the maximum speed.

As the SDK states, those default values are “realistic” in the sense that you don’t stop experiencing a crosswind just because you stop moving.

When I was playing around with the 172, and keeping that in mind, I left those values at “-1000”, and concentrated on the tyre friction instead. The first two feel a bit of a cheat, if you see why I mean.

I think the tyre friction, instead of just being those two static values, should have other factors included, such as aircraft weight. It stands to reason that an empty plane would exert less force on the ground than one at max weight.

2 Likes
93

I’m an engineer and I thought I’d weigh in here. What you set with those variables is the tyre friction coefficient. It’s not to do with the force exerted on the tyres. The friction force is the product of the load times the coefficient. The load on the wheels is actually accounted for already. You notice that if you push the yoke forward the nose wheel steering becomes more effective. I think one thing that needs improving is the effect of lateral friction when turning the wheels. Obviously when you turn it, it will slide a bit. There is always a bit of slip. That’s why the steering during taxi lacks the usual delay or lag you get when turning the front wheel. Furthermore, the system doesn’t consider the contact area. Obviously, the bigger the contact area the higher the friction coefficient. The size of that area depends on how compressed the tyres are and the pressure in them. Lastly, temperature also has an effect on the friction coefficient. All those effects still have to be implemented. Well, at least the coefficient changes with speed now which is a big step forward.

3 Likes
94

Thanks for your insight. Altering those two values certainly makes turning easier in strong crosswinds. Changing it from “1” to “10” makes it possible to turn into a 15kt crosswind, with “1” being impossible at speeds between ~10-40kts.

I preferred that option rather than just turning the crosswind off at certain speeds.

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95

I will try increase 1. The plane can be hard to controll in crosswinds.

96

10 works quite well, still needing near maximum rudder deflection, and aileron to stay near or on the centreline. I had jumped straight to 10 from 2 as I wasn’t seeing much in the way of change, which has been explained above by way of the “resync” feature which I will play with tonight, so I don’t know how far back from 10 you can get away with. My amateurish way of looking at it is if you can land a 172 in a 15kts crosswind, and make a good job of staying on or near the centre line, those values may be close to what you need.

But 1 just isn’t enough.

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97

I use 10 too :slight_smile: I wonder what type of tires 10 means :man_shrugging: Maybe slicks :slight_smile:

Maybe, in the future that value can be dynamic and make the tires get worse everytime we land :slight_smile: When it gets down to 0 we get puncture.

98

As I mentioned before 0, and 1 have you lose control as soon as you hit ~10kts. 2 was little better than that. 10 allowed me to stay on the centreline, and at those in-between speeds of ~25-40kts, I had enough friction to turn into the wind enough to be able to zig zag across the centre line between the stripes.

I haven’t actually tried commenting out all four of those lines to see how a pre-SU10 172 handles 15kts. That in itself would be interesting.

I also haven’t tried out some asymmetry, if that makes sense, having different values for main gear, and nose gear.

I might make sense to have slightly higher friction for the main gear than the nose gear.

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99

It’s so much improvement that can be done with ground physics. Microsoft own forza, hope those devs can help out with tiremodel

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100

Completely different Game-Engine. You can not copy “physics” from one engine to the other, usually. But yeah, improvement can be done for sure. :slight_smile:

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